# HSC Physics Notes Motors and Generators

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 HSC Physics Notes Motors and Generators Motors use the effect of forces on current-carrying conductors in magnetic fields 1. discuss the effect on the magnitude of the force on a current-carrying conductor of variations in the strength of the magnetic field in which it is located Force is proportional to the magnetic field strength (B). i.e. F = B the magnitude of the current in the conductor The force is proportional to the current (I) in the conductor. i.e. F = I the length of the conductor in the external magnetic field The force is proportional to the length (l) of the conductor. i.e. F = l the angle between the direction of the external magnetic field and the direction of the length of the conductor The force is at a maximum when conductor is at right angles to the field. The force is equal to zero when the conductor is parallel to the field. F = Θ. F = BIlsin Can be used to determine force in a magnetic field 2. explain qualitatively and quantitatively the force between long parallel current-carrying conductors Because we know that a wire carrying a current will produce a magnetic field, thus it will exert forces upon other fields or objects near or in the field. When two long parallel current-carrying conducting wires (known as a solenoid) are placed side by side with a finite distance between them, their magnetic fields will affect each other. If the current is flowing in the same direction in both conductors, the fields will attract (making a combined, larger field) If the currents of the conductors are flowing in opposite directions, the magnetic fields will repel from each other. d The right-hand grip rule can also be applied to determine the direction of flow of current and thus whether the two long parallel current-carrying conducting magnetic fields exert repelling or attracting fields with relation to each other. Determining the magnitude of force between two parallel current-carrying conducting wires is given by the following equation: F l = k I 1 I 2 d where; F = the force acting upon the length of a conductor (N) l = length of chosen conductor (m) k = constant (derived through careful analysis + testing) = 2.0 x 10-7 N A -2 I 1 and I 2 = current of either conductor (amps) d = distance between conductors (m) 3. define torque as the turning moment of a force using: = Fd Torque is the turning effect of an object when force is acting upon it. The torque of an object is greater when the distance of the force from the pivot point (where the torque occurs) is further away. Thus, as distance increasing, so does the torque of an object.

2 If the force applied is perpendicular to the line joining the point of application of the force and the pivot point, the following formula can be used: = Fd where; т = Torque of an object (Newton metre Nm) F = Force (N) d = Distance from the point of application to the pivot point (m) 4. identify that the motor effect is due to the force acting on a current-carrying conductor in a magnetic field A current-carrying conductor produces a magnetic field. When the current-carrying conductor passes through an external magnetic field, the magnetic field of the conductor interacts with the external magnetic field and the conductor experiences a force. This effect was discovered in 1821 and is known as the motor effect. The direction of the force on the current-carrying conductor can be determined using the right hand push rule remembering that magnetic field lines go from north to south. 5. describe the forces experienced by a current-carrying loop in a magnetic field and describe the net result of the forces If a current-carrying wire (loop) is present in an external magnetic field, then the current-carrying conductor will experience forces exerted upon it. Applying the right hand push rule, one can determine the direction of force on the loop in the external magnetic field. The force acting on the sides of the coil that are perpendicular to the magnetic field can be calculated using: F = nbilsin where; F = Force (N) B = Magnetic field strength I = Current (A) l = length of current-carrying conductor (m) n = number of loops in wire coil armature This extra force on each side of the conductor increases the torque of the armature (the rotational device which motors the motor). This torque in turn rotates the coil to a point where the current-carrying conductors are parallel with the magnets and the magnetic field however momentum pushes the armature further around to the perpendicular position where the split-ring commutator changes the direction of current so the rotor can continue rotating in the same direction. The net force is a continual rotation determined by the right hand push rule at a magnitude calculated by the above formula. 6. describe the main features of a DC electric motor and the role of each feature The DC electric motor relies on the motor effect to create a continuous spinning motion in which a current must be continuously supplied into the motor to keep the magnetic fields interacting and the external field exerting forces on the current-carrying conductors. The main features are: Armature the ferromagnetic cylinder which rotates on an axle to produce the rotational motion of the DC electric motor. Coil is wrapped/coiled around the armature on opposite sides so that the current changes direction about the armature. It is responsible for giving the current a medium to flow. Split-ring commutator is used so that the current is kept perpendicular to the magnetic field lines. The commutator's role is to change the direction of the current at the right point to ensure the armature continues rotation in the same direction. Brushes are used to keep the current flowing into the commutator without sparking. Magnets produce the external magnetic field which interacts with the field produced by the coiled wire about the armature.

3 7. identify that the required magnetic fields in DC motors can be produced either by current-carrying coils or permanent magnets The magnetic field of a DC motor can be provided either by permanent magnets or by electromagnets. The permanent magnets are fixed to the body of the motor. Electromagnets can be created using a soft iron shape that has coils of wire around it. The current that flows through the armature coil can be used in the electromagnet coils. 1. solve problems using: F = k I I 1 2 l d Which simply involves practising questions where there are two long parallel current-carrying conductors to determine the force between them. 2. perform a first-hand investigation to demonstrate the motor effect Wire + Electronic Balance: The current-conducting wire is placed on an electronic balance which passes between two oppositely 'polarised' magnets i.e. one north and one south. When the wire is balanced on the electronic scales, it is zeroed. When the current is pushed through the current-carrying wire the balance will record a positive or negative value depending on the direction of the current however, despite whether the reading displayed is negative or positive, the fact that there is a change in magnitude shows the wire is experiencing a force exerted upon it. This force is a result of the interaction of the external magnetic field between the two magnets and the produced field from the wire. This shows the motor effect. 3. solve problems and analyse information about the force on current-carrying conductors in magnetic fields using: F = BIlsin A current-carrying conductor in a magnetic field creates a force. where; F = Force (N) B = Strength of magnetic field (T) I = Current (A) l = length of current-carrying conductor (m) θ = angle at which the conductor is at to the direction of the magnetic field The direction of the current can be obtained using the right hand push rule. 4. solve problems and analyse information about simple motors using: = nbiacos where; τ = Torque (Nm) n = number of coils B = Strength of magnetic field (T) I = Current (A) θ = angle between magnetic field lines and plane of coil 5. identify data sources, gather and process information to qualitatively describe the application of the motor effect in: the galvanometer A galvanometer is used to measure the magnitude and direction of direct current (DC). It uses the motor effect to do this. A coil consisting of many loops is connected in series and coiled around a soft iron core. When the current flows through the current-carrying wire, the coil experiences a force due to the presence of an external magnetic field exemplifying the motor effect.

4 The needle attached to the core is rotated until the magnetic force acting on the coil is equalled by a counter balancing, tensioned spring. The magnets are curved around the coil, thus shaping the magnetic field surrounding into a radial shape so the plane of the coil will always be parallel with the magnetic field. This also results in constant torque as the coil/spring rotate therefore making the scale of the galvanometer linear so that the force current. the loudspeaker Loudspeakers are used to transform electrical energy (impulses) into sound energy. A loudspeaker consists of a circular magnet that has one pole on the outside and the other on the inside. The voice coil sits in between the poles (essentially wrapped around the centre core) which is connected to an amplifier which produces the amplified sound. This voice coil is caused to vibrate or move in and out of the magnet due to the motor effect. The force acting upon the magnetic field produced from the coil pushes the amplified waves out of the speaker cone so that it can be heard. The field lines of the permanent magnets are always perpendicular to the current in the coil. 2. The relative motion between a conductor and magnetic field is used to generate an electrical voltage 1. outline Michael Faraday s discovery of the generation of an electric current by a moving magnet Michael Faraday discovered that when moving a bar magnet (or any type for that matter) through a coil of wire that an electrical current was produced. This is the opposite of the motor effect and is known as induction. Relative motion between a magnet and a coil induce a current, in which the strength of the current being induced can be changed by the relative speed of the magnet through/around the coil of wire (faster magnet, larger current). Faraday noticed that when putting the north end of a magnet into a coil, the current began to flow and direction could be determined. When pulling the magnet in the opposite direction, the direction of the current changed concurrently. 2. define magnetic field strength B as magnetic flux density The strength of a magnetic field, B, is also known as the magnetic flux density. In the SI system, B is measured in Tesla (T) or Weber per square metre (Wb m 2 ). It is also important to note that the stronger a magnetic field is (stronger magnetic flux), the closer the field lines will be when drawing. Magnetic flux is given the symbol: B 3. describe the concept of magnetic flux in terms of magnetic flux density and surface area Magnetic flux is the name given to the amount of magnetic field passing through a given area. If the particular area, A, is perpendicular to a uniform magnetic field of strength B (as shown in figure 7.8 on the opposite page) then the magnetic flux Φ B is the product of B and A. So to calculate magnetic flux, multiply the normal magnetic flux density component by the area through which the magnetic field lines are passing. = B A B

5 4. describe generated potential difference as the rate of change of magnetic flux through a circuit The generated potential difference (or voltage) is equal in magnitude to the rate at which the magnetic flux through the circuit is changing with time. The equation derived to calculate the total generated potential difference is as follows: = B The negative sign indicates the direction of the induced emf. t where; ε = generated potential difference (V) Ф B = magnetic flux density (T) t = time (s) 5. account for Lenz s Law in terms of conservation of energy and relate it to the production of back emf in motors Lenz s Law states that an induced current is always in a direction such that its magnetic field opposes the changing field that created it. Lenz s Law is a result of conservation of energy. We know that energy cannot be created or destroyed and as a result of this, Lenz's law applies to the generation of back emf in motors (and the motor effect). It applies as following: If we have a current flowing through a wire in the presence magnetic field in a motor, then this will cause the coil to spin. However, this relative motion between the rotating current-carrying coil and the magnetic field will produce a current (as a result of the motor effect and induction). This current, in the same direction as the initial current, would grow infinitely larger and eventually overload the system; also producing energy from no work. This would break the law of conservation of energy. Thus, the current produced as a result of the rotating coil flows in the opposite direction, conserving the system's energy this is known as back emf. When the coil of a motor rotates, a back emf is induced in the coil due to its motion in the external magnetic field. Therefore, Lenz identified this issue and devised his law (above). 6. explain that, in electric motors, back emf opposes the supply emf Due to Lenz's law and the result of a back emf in a rotating coil within a motor, there must be energy conserved throughout the system. For this to occur, the back emf that is induced must oppose or flow in the opposite direction of the supplied emf that is being put into the system. The smaller the back emf is, he greater the current flowing through the coil. When the motion of the coil is resisted, say by a load, then the coil will be spinning slower and so the back emf (which is induced due to the relative motion of a coil and a magnetic field) will be less. Therefore the net voltage in a motor is the supply voltage minus the produced back emf. Note: Preliminary formulas may need to be used in questions, such as V = IR 7. explain the production of eddy currents in terms of Lenz s Law Eddy currents are produced between the relative movement of a metal (not necessarily magnetic) and a magnetic field. They are small circular paths. Due to resistance eddy currents produce heat and these currents produce a magnetic field that, due to Lenz s law, opposes the original changing magnetic field. The right hand push rule can be applied to determine the direction of the force on the eddying current (which is meant to resemble the swirl of water after a boat takes off). An eddy current can be produced or mimicked by dropping a small magnet down a metallic (preferably non-magnetic) tube. As the magnetic makes relative movement to the metal, swirling eddy currents will be produced vertically down the cylinder in big rings.

6 1. perform an investigation to model the generation of an electric current by moving a magnet in a coil or a coil near a magnet A permanent magnet was moved from left to right through an insulated coil of wire to generate a current in the coil. The coil was attached to a multimeter on each end to measure the current flowing through. As the magnet approached from the left, the multimeter measured a small current which in turn produced a magnetic field which opposed the magnetic field produced by the permanent magnet making it harder to push through. When the bar was placed in the middle, the induced current travelled in the same direction (toward to the magnet) as before but the current was far stronger due to the larger magnetic flux in the centre. Upon removing the magnet out the right side of the magnet, the current lowered again to approximately the same amperes as before putting the magnet in. The current was still in the same direction. If I were to reverse the poles of the magnet (i.e. turn it around) then the induced current would travel in the opposite direction as before; this is to ensure the magnetic field produced by the induced current opposes the permanent magnets field due to Len's Law. Note: The right hand grip rule was applied to verify that the two magnetic fields opposed each other however this could be physically felt by their repulsion. 2. plan, choose equipment or resources for, and perform a first-hand investigation to predict and verify the effect on a generated electric current when: same experiment as above the distance between the coil and magnet is varied As the distance is increased the strength of the magnetic field decreases thus less current is induced. This was verified by numerous repeated tests at many lengths of 3cm further away each time. D = A the strength of the magnet is varied As the strength of the magnet increased, the induced current was greater (and thus the induced magnetic field was greater too). This was tested with varying strength in magnets so the flux was different for each test. B = A the relative motion between the coil and the magnet is varied The faster the relative movement between the coil and magnet, the greater the induced current. V = A 3. gather, analyse and present information to explain how induction is used in cooktops in electric ranges Induction cooktops use the fact that a conductor in the presence of a changing magnetic field will have induced eddy currents created which create a magnetic field to oppose the first magnetic field. Induction cooktops have a coil beneath the surface which AC power is supplied to (DC power would not work as the magnetic field is required to vary so a varying current is needed) which in turn produces a varying magnetic field. The changing magnetic field beneath the cooktop induces eddy currents in the metallic pan and also agitating the actual atoms within the pan/pot. Due to the resistance (a property or an eddy current), heat is given off into the metallic pan/pot to cook the food. The rapidly changing magnetic field(s) directly heat up the metallic object on top so no heat is lost, compared to the older gas or heated coil style of cooktops. 4. gather secondary information to identify how eddy currents have been utilised in electromagnetic braking Electromagnetic braking systems utilise eddy currents to interact with electromagnets as to create a stopping force for moving vehicles.

7 The electromagnetic brakes consist of electromagnets positioned on either side of a rotating disc. The electromagnets will be creating a magnetic field as a result of the current flowing through them; and as a result of Len's Law, the spinning disc (nonmagnetic) will interact with this magnetic field, producing eddy currents. These eddy currents produced as a result of the relative motion between the disc and electromagnetic fields will produce their own magnetic field which opposes the electromagnetic field which is the braking force. Electromagnets are chosen rather than permanent magnets, because the electromagnets can be switched off when not needing to brake (so there is no magnetic field while the disc spins). The strength of the magnetic field from the electromagnets can be increased by increasing the current in them, resulting in hard or soft braking. 3. Generators are used to provide large scale power production 1. describe the main components of a generator The DC generator functions exactly the same as a motor but simply in reverse. Instead of creating torque due to the current flowing through the motor; in a generator a current is generated from the spinning of the central armature the torque. The stationary parts of a generator are called the stator, while the moving parts are known as the rotor. You can determine the magnitude and direction of torque using: = nbiacos 2. compare the structure and function of a generator to an electric motor Because the operation of a motor and generator are simply in reverse, then the generator and the motor can in fact be the device, however, power station generators are different. A power station generator produces AC current. It has the magnetic field rotating inside a stationary coil. Solenoid, creates Front View: Rear View: magnetic field from DC current. AC ouput Rotor, which is rotated. Spilt ring commutator and brushes are added to allow DC supply for solenoid. Stator, generating coil (current is induced due to changing. To determine the direction of the current in a generator, the right hand push rule can be modified. Where fingers are the direction of magnetic field, thumb is the direction of turning motion and palm is the direction of the current in the wire.

8 3. describe the differences between AC and DC generators AC and DC generators operate in the same way, but generate different kinds of electricity. Slip rings are used in the AC generators, while a simple split-ring commutator is used in the DC generator. AC Generators are preferred because: Slip rings won't wear down or break as easily as split ring commutators Mains power is AC; therefore there is no need for a DC to AC converter when AC generators are in use Both the AC and DC generators are used to transform mechanical kinetic energy into electrical energy. The energy output from either of these generators can be represented graphically: AC Voltage Generation The AC generator's voltage output represents a sine wave curve (right) while the DC generator will be the same, however, not produce negative values. The AC generator alternates its current output in intervals, whereas the DC generator is a constant flow in the one direction. 4. discuss the energy losses that occur as energy is fed through transmission lines from the generator to the consumer Power stations and generators are most often located large distances away from the centre of busy cities where most people reside. This long distance presents problems in transferring electricity to those in the large CBD areas which are so far away. We know (and see) that the large power cables overhead or beneath the ground in some cities are used to transport electricity to households are businesses; however, the length and size of these wires resists the flow of electricity. The resistance of the wires used to transport electricity to the consumer is the most costly and inefficient part of the process. The resistance (R) of the metallic conducting wire is proportional to it's resistivity and length, also inversely proportional to it's area. Thus: R = where; R = overall resistance of the wires p = resistivity of the wires (depending on type of wire) l = length (m) A = area Now, by the knowledge that V = IR we can determine the power loss. P = VI, thus by multiplying both sides of the first formula by I, we determine that P loss = I 2 R The significant resistance which the long metallic wires pose can be minimised by forcing the electricity through at a higher voltage (emf) The implementation of transformers across the country has enabled household and infrastructure powered by electricity to succeed because they allow the transfer of electricity over long distances with minimal resistance. Transformers and substations are used to step-up and stepdown the AC electricity so that the resistance along the transfer is negated with a voltage boost. 5. assess the effects of the development of AC generators on society and the environment Society: The production AC generators have allowed the transfer of AC electricity to domestic homes which are used to power lights, cooking utensils, refrigerators etc. Without AC electricity, modern man would not survive in terms of food gathering and cooking. Many businesses require electricity to power many machines to operate their company. Without the introduction of AC generators there could not have been simple electronics in homes. Has laid the foundations for infrastructure to be built and continued technology now relies on pl A

10 Westinghouse AC electricity Bought the patents and works of Tesla for \$1,000,000. The invention of the electric chair (and what type of electricity to use) The Niagara Falls Power Plant project was established to give the winner money if they could utilise the power of the falls in a generator. Westinghouse's AC design won this competition. The Electric Chair War. AC was deemed to be more efficient because it could be stepped down using transformers from 300kV down to 240V mains power. 4. gather and analyse information to identify how transmission lines are: insulated from supporting structures Transmission lines have the possibility to spark in dry and humid air. In dry air, a wire will spark 1cm for every 10kV and so most high voltage wires are approximately 330kV, therefore sparking 33cm (and even more in humid conditions). To prevent these sparks from reaching other cables and the structures which support the cables, insulators are used to separate them. insulator These insulators are often numerous discs (which increase the leakage distance) in a straight line, ceramic make because of its great insulating nature, and extend about cm in length to prevent the wires from interacting with the structure. protected from lightning strikes When lightning strikes from the bottom of the storm cloud, it will do so at the highest point on the earth which can often be the towers carrying high voltage power lines. These power lines are fitted with one earth cable which carries no current. The continuous earth line can be used to carry a current in times when other lines fail, however the earth line can be used to carry extremely high voltage lightning strikes into the Earth. 4. Transformers allow generated voltage to be increased or decreased before it is used 1. describe the purpose of transformers in electrical circuits Transformers are used in electrical domestic circuits and appliances to change the voltage in appliances so that they can function or perform their task. Voltage and current are directly related (V = IR) so that when voltage is increased, current must decrease. However, power (P = I 2 R) stays the same. 2. compare step-up and step-down transformers Primary Coil Secondary Coil AC current is required for a transformer to operate because it requires an alternating magnetic field. Step-up transformers increase the voltage of the system, and Step-down transformers will decrease the emf. Transformers operate on the fact that alternating magnetic fields produce a changing current.

11 Transformers which step down will have the primary coil at a higher voltage than the second, and to do this (since they are proportionally related by V = IR) then the second coil will have a lower voltage, however higher current. Step-up transformers have the power coming into the first coil at a high current, and is then lowered to increase the voltage (emf). 3. identify the relationship between the ratio of the number of turns in the primary and secondary coils and the ratio of primary to secondary voltage V p V s = n p n s If n s is greater than n p, the output voltage, V s, will be greater than the input voltage, V p. Such a transformer is known as a step-up transformer. If n s is less than n p, the output voltage, V s, will be less than the input voltage, V p. Such a transformer is known as a step-down transformer. The number of turns in the coil are also important. If there are more turns on the primary coil, but less on the secondary, then the transformer will be a step-down transformer as it increases current and decreases voltage. Note: because the voltage enters the primary coil, this is the input voltage. The voltage exists the secondary coil and is therefore the output voltage. In an ideal situation where the input and output voltages are equal, therefore the input and output currents of both must equal. 4. explain why voltage transformations are related to conservation of energy Transformers are related to the conservation of energy because they 'transform' energy from one state to another. The Law of Conservation of Energy states that no energy can be created nor destroyed there must be a trade-off or transforming of energy. The power which is injected into the primary coil can not exceed the power which is ejaculated from the secondary coil. This is related by the property: P = IV. The voltage and current can be, however, altered and this is what function transformers and transformations of energy within them act on. One would notice that not all the magnetic flux of the system is transferred to the secondary coil due to the production of eddy currents and production of heat as a result, which is then given off as thermal energy. 5. explain the role of transformers in electricity sub-stations Transformers must be used to allow electricity to be efficiently transferred to consumers in a fast, economic manner. We know that voltage in transmission lines will decrease based on the area, length and resistivity of the wire so it is sent at extremely high voltages to reduce this loss. However, the voltages are so high that they cannot possibly be sent to domestic homes for appliance or lighting operation this would cause fires and short fuses. To decrease the power and voltage of the electricity sent to homes, transformers are used to step-down the voltage. Substations are positioned across each state so that there are regular intervals that the voltage can be stepped up (for long distances as a result of loss) or stepped down to be transferred into homes. 6. discuss why some electrical appliances in the home that are connected to the mains domestic power supply use a transformer The mains power in a home is a stable 240V alternating current which is far than sufficient to power numerous household appliances at once. Most electrical appliances do not need to utilise the full 240V of power however, most only needing 12-24V, for this to occur a transformer needs to be used to step down the voltage of from the mains box otherwise the appliance would short out with too high (maximum) current flowing through the electrical circuit. However, some extremely large appliances which drain large levels of power such as large TVs and other high demand appliances require more than 240V. For this reason, such appliances contain a transformer to step up the voltage, however, lowing the current in the circuit. If these appliances were not able to get the required voltage above 240V, they simply wouldn't have the power to turn on or function.

12 7. discuss the impact of the development of transformers on society Transformers have allowed different voltage appliances to exist and operate perfectly in homes at lower voltages. Transformers have allowed 240V mains power to be lowered (or increased) and thus allowing toasters to operate, computers etc. The introduction of transformers have made homes safer when utilising electricity at lower voltages. The invention and implementation of transformers have resulted in the need for only one type of electricity (AC) and same mains voltage to homes. Transformers with the ability to step-up voltage allow electricity to be transported long distances as they can be stepped up into high kv (this is needed since electricity loses voltage across transmission lines). As a direct result of transformers possessing the ability to transfer electricity at higher voltages, and therefore minimising energy loss, consumers can save on money and costs compared if the electricity were transported at lower voltages. 1. perform an investigation to model the structure of a transformer to demonstrate how secondary voltage is produced A secondary voltage is induced in transformers due to Lenz's Law. When a current flows through the first (primary) coil, a magnetic field will be produced which covers the secondary coil entirely. Accordingly, with Lenz's Law, this secondary coil will also produce a current through it's coils. The voltage/current can be altered by changing the ratio of coils on each of the coils. Refer to model. Through experimentation, I found that the ratio of coils from primary to secondary coil was directly proportional to the ratio of voltage on each coil. I noticed, however, that this proportional correlation was affected because of the transfer of energy in the vibration of the transformer and also in the release of heat (minimised through the insulation of coil and lamination to prevent high eddy currents). 2. solve problems and analyse information about transformers using: V p V s = n p n s This formula demonstrates the direct proportion between the voltage in the solenoid to the respective number of coils on that conductor. This formula can be further extended to: V p V s = n p n s = I S I P 3. gather, analyse and use available evidence to discuss how difficulties of heating caused by eddy currents in transformers may be overcome Due to the high current that is input into the primary coil, a large and strong magnetic field is created which envelops the secondary solenoid. The interaction between the magnetic field and the metallic structure and ferrous, soft-iron core causes large eddy currents to develop and as a result, heat is produced and amplified in the same way that induction cooktops work. The heat is minimised in the following ways: Lamination: By lamination the iron core of the transformer, we insulate the transformer and will not conduct very much heat so that more energy can be transferred to the secondary coil. By using insulating lamination techniques, we can optimise the efficiency of the transformer by preventing large eddy currents from forming and instead, much smaller heat producing eddy currents are formed, reducing the amount of energy lost in the form of heat. Ferrites: May be used instead of an iron core. Ferrites are an impure mixture of iron ores and other substances which are bad conductors of heat and electricity. By minimising the amount of metallic core, we optimise the efficiency of the transformer as there is less area for eddy currents to form. Coolant: Obviously does not minimise the amount of eddy currents produced and therefore does not increase the efficiency of the system. Coolants are used to prevent transformers from overheating when eddy currents cannot be reduced by aforementioned techniques.

13 4. gather and analyse secondary information to discuss the need for transformers in the transfer of electrical energy from a power station to its point of use i) AC electricity is generated in power stations, most commonly by the combustion of fossil fuels in order to rotate a turbine which powers a generator to create electricity. ii) Electricity is stored until it reaches sufficient power and is stepped up using a transformer to voltages approximately 330kV across high power transmission lines as an AC power source. iii) Power does not need to be stepped up and down along the way to it's domestic or industrial use because of the efficiency to transport AC electricity over long distances. iv) A transformer, located in the most suitable (and close) vicinity which is steps down the electricity to approximately 11000V which is then split and distributed to a small 'power box' which contains a step down transformer. v) The voltage is then stepped down to 240V mains power using the step-down transformer located near or at the house. 5. Motors are used in industries and the home usually to convert electrical energy into more useful forms of energy 1. describe the main features of an AC electric motor There are two types of AC electric motors: AC Synchronous Motor: Cylindrical rotor and same stator parts as DC motor Slip rings Electromagnets to provide a rapidly changing magnetic field that induce the alternating current AC Induction Motor: Squirrel Cage: in which long bars of copper are attached on rings at either end that allow a current to pass from one end to the other Operates using AC powered electromagnets which create a rotating and changing magnetic field in the stator which is outside the rotor. The paired magnets change polarity with the AC phase, resulting in a torque. The changing magnetic field will induce a current in the long bars that will also produce a magnetic field to oppose the one that created it. This opposition because of the induced current creates the force, torque, which spins the rotor

14 1. perform an investigation to demonstrate the principle of an AC induction motor A sheet of aluminium foil was placed on top of a pool of water. This allows the aluminium foil to move and spin. When a magnet above the foil is spun the aluminium sheet also spins. This is due to Lenz s Law, where the aluminium foil will induce eddy currents to create its own magnetic field which opposes the original changing magnetic field. The interaction of these two magnetic fields causes the aluminium foil to spin. 2. gather, process and analyse information to identify some of the energy transfers and transformations involving the conversion of electrical energy into more useful forms in the home and industry Since energy cannot cannot be destroyed or created, it is therefore only ever converted from one type to the next and utilised in the house and industry for many pracitcal applications. Using electrical energy, the household television is a prime example of the conversion of electrical energy into light energy (the picture we see), sound energy (the music and sound we hear); and the same can be applied to hair dryers which convert electrical energy to kinetic energy to rotate a motor which converts this kinetic energy into heat energy through heat plates. kinetic energy or heat energy or sound energy or gravitational potential energy or chemical energy The industry is also able to access this fundamental property of the conversion of energy from one state to the next. In industry, lifts (elevators) and escalators use the conversion of electrical energy to create both a kinetic energy to move people from one place to another but in the same process then gain and convert into a gravitational potential energy by going up and down. Car batteries are an example of the conversion of electrical energy into chemical energy for storage when they are recharged.

### Chapter 14 Magnets and

Chapter 14 Magnets and Electromagnetism How do magnets work? What is the Earth s magnetic field? Is the magnetic force similar to the electrostatic force? Magnets and the Magnetic Force! We are generally

### Chapter 22: Electric motors and electromagnetic induction

Chapter 22: Electric motors and electromagnetic induction The motor effect movement from electricity When a current is passed through a wire placed in a magnetic field a force is produced which acts on

### Name: Date: Regents Physics Mr. Morgante UNIT 4B Magnetism

Name: Regents Physics Date: Mr. Morgante UNIT 4B Magnetism Magnetism -Magnetic Force exists b/w charges in motion. -Similar to electric fields, an X stands for a magnetic field line going into the page,

### Question Bank. 1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction

1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction 1. Diagram below shows a freely suspended magnetic needle. A copper wire is held parallel to the axis of magnetic

### 1. The diagram below represents magnetic lines of force within a region of space.

1. The diagram below represents magnetic lines of force within a region of space. 4. In which diagram below is the magnetic flux density at point P greatest? (1) (3) (2) (4) The magnetic field is strongest

### GENERATORS AND MOTORS

GENERATORS AND MOTORS A device that converts mechanical energy (energy of motion windmills, turbines, nuclear power, falling water, or tides) into electrical energy is called an electric generator. The

### MAGNETISM MAGNETISM. Principles of Imaging Science II (120)

Principles of Imaging Science II (120) Magnetism & Electromagnetism MAGNETISM Magnetism is a property in nature that is present when charged particles are in motion. Any charged particle in motion creates

### Chapter 14 Magnets and Electromagnetism

Chapter 14 Magnets and Electromagnetism Magnets and Electromagnetism In the 19 th century experiments were done that showed that magnetic and electric effects were just different aspect of one fundamental

Copyright 2014 Edmentum - All rights reserved. Science Physics Electromagnetic Blizzard Bag 2014-2015 1. Two coils of insulated wire are placed side by side, as shown in the illustration. The blue lines

### And in un-magnetized state, the molecular magnets are arranged randomly.

MAGNETISM A magnet is a piece of metal that attracts other metals. It has two poles i.e. North Pole and South Pole A pole This is a point or an area in a magnet where the attractive power seems to be concentrated.

### MAGNETIC EFFECTS OF ELECTRIC CURRENT

CHAPTER 13 MAGNETIC EFFECT OF ELECTRIC CURRENT In this chapter, we will study the effects of electric current : 1. Hans Christian Oersted (1777-1851) Oersted showed that electricity and magnetism are related

### BASANT S SCIENCE ACADEMY STUDY MATERIAL MAGNETIC EFFECT OF CURRENT

BASANT S SCIENCE ACADEMY Why does a compass needle get deflected when brought near a bar magnet? A compass needle is a small bar magnet. When it is brought near a bar magnet, its magnetic field lines interact

### 1. E&M induction requires change, of the intensity of a magnetic field or of motion in a magnetic field.

Chapter 25 EXERCISE key 1. E&M induction requires change, of the intensity of a magnetic field or of motion in a magnetic field. 2. Magnetic induction will not occur in nylon, since it has no magnetic

### In order to get the G.C.S.E. grade you are capable of, you must make your own revision notes using your Physics notebook.

In order to get the G.C.S.E. grade you are capable of, you must make your own revision notes using your Physics notebook. When summarising notes, use different colours and draw diagrams/pictures. If you

### physics 112N electromagnetic induction

physics 112N electromagnetic induction experimental basis of induction! seems we can induce a current in a loop with a changing magnetic field physics 112N 2 magnetic flux! useful to define a quantity

### Magnetism Basics. Magnetic Domains: atomic regions of aligned magnetic poles Random Alignment Ferromagnetic Alignment. Net Effect = Zero!

Magnetism Basics Source: electric currents Magnetic Domains: atomic regions of aligned magnetic poles Random Alignment Ferromagnetic Alignment Net Effect = Zero! Net Effect = Additive! Bipolar: all magnets

### Motor Fundamentals. DC Motor

Motor Fundamentals Before we can examine the function of a drive, we must understand the basic operation of the motor. It is used to convert the electrical energy, supplied by the controller, to mechanical

### Pearson Physics Level 30 Unit VI Forces and Fields: Chapter 12 Solutions

Concept Check (top) Pearson Physics Level 30 Unit VI Forces and Fields: Chapter 1 Solutions Student Book page 583 Concept Check (bottom) The north-seeking needle of a compass is attracted to what is called

### Copper and Electricity: Generation

PHYSICS Copper and Electricity: Generation (Electromagnetic Induction) 16-18 YEARS Below are different sections of this e-source, for quick navigation. Electricity from Movement What is Induction? Flux

### ELECTRODYNAMICS 05 AUGUST 2014

ELECTRODYNAMICS 05 AUGUST 2014 In this lesson we: Lesson Description Discuss the motor effect Discuss how generators and motors work. Summary The Motor Effect In order to realise the motor effect, the

### Chapter 19 Magnetism Magnets Poles of a magnet are the ends where objects are most strongly attracted Two poles, called north and south Like poles

Chapter 19 Magnetism Magnets Poles of a magnet are the ends where objects are most strongly attracted Two poles, called north and south Like poles repel each other and unlike poles attract each other Similar

### ElectroMagnetic Induction. AP Physics B

ElectroMagnetic Induction AP Physics B What is E/M Induction? Electromagnetic Induction is the process of using magnetic fields to produce voltage, and in a complete circuit, a current. Michael Faraday

### Chapter 14: Magnets and Electromagnetism

Chapter 14: Magnets and Electromagnetism 1. Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when viewed from above. This causes a magnetic field. Inside

### The purposes of this experiment are to test Faraday's Law qualitatively and to test Lenz's Law.

260 17-1 I. THEORY EXPERIMENT 17 QUALITATIVE STUDY OF INDUCED EMF Along the extended central axis of a bar magnet, the magnetic field vector B r, on the side nearer the North pole, points away from this

### Level 2 Physics: Demonstrate understanding of electricity and electromagnetism

Level 2 Physics: Demonstrate understanding of electricity and electromagnetism Static Electricity: Uniform electric field, electric field strength, force on a charge in an electric field, electric potential

### Physics 12 Study Guide: Electromagnetism Magnetic Forces & Induction. Text References. 5 th Ed. Giancolli Pg

Objectives: Text References 5 th Ed. Giancolli Pg. 588-96 ELECTROMAGNETISM MAGNETIC FORCE AND FIELDS state the rules of magnetic interaction determine the direction of magnetic field lines use the right

### AP Physics C Chapter 23 Notes Yockers Faraday s Law, Inductance, and Maxwell s Equations

AP Physics C Chapter 3 Notes Yockers Faraday s aw, Inductance, and Maxwell s Equations Faraday s aw of Induction - induced current a metal wire moved in a uniform magnetic field - the charges (electrons)

### STUDY GUIDE: ELECTRICITY AND MAGNETISM

319 S. Naperville Road Wheaton, IL 60187 www.questionsgalore.net Phone: (630) 580-5735 E-Mail: info@questionsgalore.net Fax: (630) 580-5765 STUDY GUIDE: ELECTRICITY AND MAGNETISM An atom is made of three

### Inductance. Motors. Generators

Inductance Motors Generators Self-inductance Self-inductance occurs when the changing flux through a circuit arises from the circuit itself. As the current increases, the magnetic flux through a loop due

### Chapter 25 Practice Problems, Review, and Assessment

Chapter 25 Practice Problems, Review, and Assessment Section 1 Inducing Currents: Practice Problems 1. You move a straight wire that is 0.5 m long at a speed of 20 m/s vertically through a 0.4-T magnetic

### DIRECT CURRENT GENERATORS

DIRECT CURRENT GENERATORS Revision 12:50 14 Nov 05 INTRODUCTION A generator is a machine that converts mechanical energy into electrical energy by using the principle of magnetic induction. This principle

### PS-6.2 Explain the factors that determine potential and kinetic energy and the transformation of one to the other.

PS-6.1 Explain how the law of conservation of energy applies to the transformation of various forms of energy (including mechanical energy, electrical energy, chemical energy, light energy, sound energy,

### 2. A conductor of length 2m moves at 4m/s at 30 to a uniform magnetic field of 0.1T. Which one of the following gives the e.m.f. generated?

Extra Questions - 2 1. A straight length of wire moves through a uniform magnetic field. The e.m.f. produced across the ends of the wire will be maximum if it moves: a) along the lines of magnetic flux

### Chapter 21 Electromagnetic Induction and Faraday s Law

Lecture PowerPoint Chapter 21 Physics: Principles with Applications, 6 th edition Giancoli Chapter 21 Electromagnetic Induction and Faraday s Law 2005 Pearson Prentice Hall This work is protected by United

### Electrical discharge in air e.g. lightning

Static Electricity electron transfer causes static electricity results from an imbalance of charges can occur by induction, friction, and contact You need to describe the direction of motion of charges

### Characteristics and Benefits

Defining Quality. Building Comfort. Characteristics and Benefits Characteristics and Benefits The two most common electronic devices to vary fan speed in HVAC equipment are the variable frequency drive

### Chapter 27 Magnetic Induction. Copyright 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley

Chapter 27 Magnetic Induction Motional EMF Consider a conductor in a B-field moving to the right. In which direction will an electron in the bar experience a magnetic force? V e - V The electrons in the

### Electromagnetic Laboratory Stations

Electromagnetic Laboratory Stations The following laboratory exercises are designed to help you study magnetic fields produced by magnets and current carrying wires, and study other well-known electromagnetic

### Chapter 20. Magnetic Induction Changing Magnetic Fields yield Changing Electric Fields

Chapter 20 Magnetic Induction Changing Magnetic Fields yield Changing Electric Fields Introduction The motion of a magnet can induce current in practical ways. If a credit card has a magnet strip on its

### ELECTROMAGNETISM I. CAUSES OF MAGNETISM

I. CAUSES OF MAGNETISM ELECTROMAGNETISM 1. Moving electric fields (moving charges) cause magnetism. Yes, that current moving in electric circuits cause a magnetic field. More later! 2. Elementary nature

### 2. TRANSFORMERS. The main learning objectives for this chapter are listed below. Use equivalent circuits to determine voltages and currents.

. TRANSFORMERS Transformers are commonly used in applications which require the conversion of AC voltage from one voltage level to another. There are two broad categories of transformers: electronic transformers,

### Chapter 7. Magnetism and Electromagnetism ISU EE. C.Y. Lee

Chapter 7 Magnetism and Electromagnetism Objectives Explain the principles of the magnetic field Explain the principles of electromagnetism Describe the principle of operation for several types of electromagnetic

### Electromagnetic Induction

Electromagnetic Induction PHY232 Remco Zegers zegers@nscl.msu.edu Room W109 cyclotron building http://www.nscl.msu.edu/~zegers/phy232.html previously: electric currents generate magnetic field. If a current

### AC generator theory. Resources and methods for learning about these subjects (list a few here, in preparation for your research):

AC generator theory This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit http://creativecommons.org/licenses/by/1.0/,

### 6. ELECTROMAGNETIC INDUCTION

6. ELECTROMAGNETIC INDUCTION Questions with answers 1. Name the phenomena in which a current induced in coil due to change in magnetic flux linked with it. Answer: Electromagnetic Induction 2. Define electromagnetic

### Objectives for the standardized exam

III. ELECTRICITY AND MAGNETISM A. Electrostatics 1. Charge and Coulomb s Law a) Students should understand the concept of electric charge, so they can: (1) Describe the types of charge and the attraction

### Reading Quiz. 1. Currents circulate in a piece of metal that is pulled through a magnetic field. What are these currents called?

Reading Quiz 1. Currents circulate in a piece of metal that is pulled through a magnetic field. What are these currents called? A. Induced currents B. Displacement currents C. Faraday s currents D. Eddy

### 2. B The magnetic properties of a material depend on its. A) shape B) atomic structure C) position D) magnetic poles

ame: Magnetic Properties 1. B What happens if you break a magnet in half? A) One half will have a north pole only and one half will have a south pole only. B) Each half will be a new magnet, with both

### Magnetic Forces and Magnetic Fields

1 Magnets Magnets are metallic objects, mostly made out of iron, which attract other iron containing objects (nails) etc. Magnets orient themselves in roughly a north - south direction if they are allowed

### Chapter 4: DC Generators

Chapter 4: DC Generators Creating an AC Voltage The voltage produced in a DC generator is inherently AC and only becomes DC after rectification Consider an AC generator, consisting of a coil on the rotor

### Electricity. Short Answer Questions QUESTIONS

S.N O Electricity Short Answer Questions QUESTIONS 1 A child has drawn the electric circuit to study Ohm s law as shown in Figure. His teacher told that the circuit diagram needs correction. Study the

### Physics 1653 Exam 3 - Review Questions

Physics 1653 Exam 3 - Review Questions 3.0 Two uncharged conducting spheres, A and B, are suspended from insulating threads so that they touch each other. While a negatively charged rod is held near, but

### Teacher Content Brief

Teacher Content Brief Electric Motors Introduction Motors convert electric energy into mechanical energy. This mechanical energy turns the propellers on your Sea Perch. But what makes a motor spin? To

### PHYS 222 Spring 2012 Final Exam. Closed books, notes, etc. No electronic device except a calculator.

PHYS 222 Spring 2012 Final Exam Closed books, notes, etc. No electronic device except a calculator. NAME: (all questions with equal weight) 1. If the distance between two point charges is tripled, the

### Chapter 31. Faraday s Law

Chapter 31 Faraday s Law Michael Faraday 1791 1867 British physicist and chemist Great experimental scientist Contributions to early electricity include: Invention of motor, generator, and transformer

### Basics of Electricity

Basics of Electricity Generator Theory PJM State & Member Training Dept. PJM 2014 8/6/2013 Objectives The student will be able to: Describe the process of electromagnetic induction Identify the major components

### Chapter 21. Magnetic Forces and Magnetic Fields

Chapter 21 Magnetic Forces and Magnetic Fields 21.1 Magnetic Fields The needle of a compass is permanent magnet that has a north magnetic pole (N) at one end and a south magnetic pole (S) at the other.

### Objectives. Capacitors 262 CHAPTER 5 ENERGY

Objectives Describe a capacitor. Explain how a capacitor stores energy. Define capacitance. Calculate the electrical energy stored in a capacitor. Describe an inductor. Explain how an inductor stores energy.

### Induced voltages and Inductance Faraday s Law

Induced voltages and Inductance Faraday s Law concept #1, 4, 5, 8, 13 Problem # 1, 3, 4, 5, 6, 9, 10, 13, 15, 24, 23, 25, 31, 32a, 34, 37, 41, 43, 51, 61 Last chapter we saw that a current produces a magnetic

### Force on Moving Charges in a Magnetic Field

[ Assignment View ] [ Eðlisfræði 2, vor 2007 27. Magnetic Field and Magnetic Forces Assignment is due at 2:00am on Wednesday, February 28, 2007 Credit for problems submitted late will decrease to 0% after

### Preview of Period 16: Motors and Generators

Preview of Period 16: Motors and Generators 16.1 DC Electric Motors What causes the rotor of a motor to spin? 16.2 Simple DC Motors What causes a changing magnetic field in the simple coil motor? 16.3

### Magnetic Field Lines. Uniform Magnetic Field. Earth s Magnetic Field 6/3/2013

Chapter 33: Magnetism Ferromagnetism Iron, cobalt, gadolinium strongly magnetic Can cut a magnet to produce more magnets (no magnetic monopole) Electric fields can magnetize nonmagnetic metals Heat and

### Lecture PowerPoints. Chapter 20 Physics: Principles with Applications, 7 th edition Giancoli

Lecture PowerPoints Chapter 20 Physics: Principles with Applications, 7 th edition Giancoli This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching

### Draw a ring around the correct answer to complete the following sentences. power supply. (1)

Q. The diagram shows a transformer made by a student. The student has designed the transformer to make a 6 V light bulb work using a 2 V power supply. (a) Draw a ring around the correct answer to complete

### Chapter 3: Electricity

Chapter 3: Electricity Goals of Period 3 Section 3.1: To define electric charge, voltage, and energy Section 3.2: To define electricity as the flow of charge Section 3.3: To explain the generation electricity

### Eðlisfræði 2, vor 2007

[ Assignment View ] [ Pri Eðlisfræði 2, vor 2007 29a. Electromagnetic Induction Assignment is due at 2:00am on Wednesday, March 7, 2007 Credit for problems submitted late will decrease to 0% after the

### EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3. OUTCOME 3 - MAGNETISM and INDUCTION

EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3 OUTCOME 3 - MAGNETISM and INDUCTION 3 Understand the principles and properties of magnetism Magnetic field:

### Chapter 23 Magnetic Flux and Faraday s Law of Induction

Chapter 23 Magnetic Flux and Faraday s Law of Induction 23.1 Induced EMF 23.2 Magnetic Flux 23.3 Faraday s Law of Induction 23.4 Lenz s Law 23.5 Mechanical Work and Electrical Energy 23.6 Generators and

### Final Exam (40% of grade) on Monday December 7 th 1130a-230pm in York 2622 You can bring two 8.5x11 pages, front and back, of notes Calculators may

Final Exam (40% of grade) on Monday December 7 th 1130a-230pm in York 2622 You can bring two 8.5x11 pages, front and back, of notes Calculators may be used multiple choice like quizzes, only longer by

### Linear DC Motors. 15.1 Magnetic Flux. 15.1.1 Permanent Bar Magnets

Linear DC Motors The purpose of this supplement is to present the basic material needed to understand the operation of simple DC motors. This is intended to be used as the reference material for the linear

### MOVING CHARGES AND MAGNETISM

MOVING CHARGES AND MAGNETISM 1. A circular Coil of 50 turns and radius 0.2m carries of current of 12A Find (a). magnetic field at the centre of the coil and (b) magnetic moment associated with it. 3 scores

### Name: Lab Partner: Section: The purpose of this lab is to study induction. Faraday s law of induction and Lenz s law will be explored.

Chapter 8 Induction - Faraday s Law Name: Lab Partner: Section: 8.1 Purpose The purpose of this lab is to study induction. Faraday s law of induction and Lenz s law will be explored. 8.2 Introduction It

### Electric Engineering II EE 326 Lecture 4 & 5

Electric Engineering II EE 326 Lecture 4 & 5 Transformers ١ Transformers Electrical transformers have many applications: Step up voltages (for electrical energy transmission with

### DC GENERATOR THEORY. LIST the three conditions necessary to induce a voltage into a conductor.

DC Generators DC generators are widely used to produce a DC voltage. The amount of voltage produced depends on a variety of factors. EO 1.5 LIST the three conditions necessary to induce a voltage into

### Chapter 22. Electromagnetic Induction

Chapter 22 Electromagnetic Induction 22.4 Faraday s Law of Electromagnetic Induction FARADAY S LAW OF ELECTROMAGNETIC INDUCTION The average emf induced in a coil of N loops is E E ) = N ' ( Φ Φ t t o o

### Worked solutions Chapter 9 Magnets and electricity

9.1 Fundamentals of magnetism 1 A magnetic field exists at any point in space where a magnet or magnetic material (e.g. iron, nickel, cobalt) will experience a magnetic force. 2 C. The magnetic force between

### Lesson 11 Faraday s Law of Induction

Lesson 11 Faraday s Law of Induction Lawrence B. Rees 006. You may make a single copy of this document for personal use without written permission. 11.0 Introduction In the last lesson, we introduced Faraday

### 10.2 Electromagnets. What is an electromagnet? Chapter 10

In the last section you learned about permanent magnets and magnetism. There is another type of magnet, one that is created by electric current. This type of magnet is called an. What is an? Why do magnets

### Electrical Machines II. Week 1: Construction and theory of operation of single phase transformer

Electrical Machines II Week 1: Construction and theory of operation of single phase transformer Transformers Overview A transformer changes ac electric power at one frequency and voltage level to ac electric

### Induced currents and Eddy Currents

Induced currents and Eddy Currents There are quite a few nice experiments you can do to demonstrate Eddy currents and induced currents with relatively cheap equipment. Equipment: Rare-earth ceramic magnets:

### Induction and Inductance

Induction and Inductance How we generate E by B, and the passive component inductor in a circuit. 1. A review of emf and the magnetic flux. 2. Faraday s Law of Induction 3. Lentz Law 4. Inductance and

### Physics Notes for Class 12 Chapter 4 Moving Charges and Magnetrism

1 P a g e Physics Notes for Class 12 Chapter 4 Moving Charges and Magnetrism Oersted s Experiment A magnetic field is produced in the surrounding of any current carrying conductor. The direction of this

### Ch.20 Induced voltages and Inductance Faraday s Law

Ch.20 Induced voltages and Inductance Faraday s Law Last chapter we saw that a current produces a magnetic field. In 1831 experiments by Michael Faraday and Joseph Henry showed that a changing magnetic

### Investigating Electrical Energy Workshop. QUT Extreme Engineering

Investigating Electrical Energy Workshop QUT Extreme Engineering Investigating Electrical Energy Introduction This workshop is designed for grades 6-7, to give them some hands-on experience in building

### Electric Generators and Motors

Electric Generators and Motors Reading Quiz: Look at the demonstration of the large electromagnet. Observe what happens (spark) when the switch is opened. What best explains this? A) The battery voltage

### Induction. d. is biggest when the motor turns fastest.

Induction 1. A uniform 4.5-T magnetic field passes perpendicularly through the plane of a wire loop 0.10 m 2 in area. What flux passes through the loop? a. 5.0 T m 2 c. 0.25 T m 2 b. 0.45 T m 2 d. 0.135

### A Practical Guide to Free Energy Devices

A Practical Guide to Free Energy Devices Part 60: Last updated: 3rd February 2006 Author: Patrick J. Kelly Electrical power is frequently generated by spinning the shaft of a generator which has some arrangement

### MAGNETISM AND ELECTRICITY

MAGNETISM AND ELECTRICITY Magnetism is a natural phenomenon first documented by the Greeks who observed that a naturally occurring substance, magnetite would attract pieces of iron. Later on, the Chinese

### Q1. (a) A transformer operating on a 230 V mains supply provides a 12 V output. There are 1150 turns on the primary coil.

Q1. (a) A transformer operating on a 230 V mains supply provides a 12 V output. There are 1150 turns on the primary coil. (i) Calculate the number of turns on the secondary coil. answer =... turns (1)

### Chapter 24 Practice Problems, Review, and Assessment

Section 1 Understanding Magnetism: Practice Problems 1. If you hold a bar magnet in each hand and bring your hands close together, will the force be attractive or repulsive if the magnets are held in the

### Electromagnetic Induction - A

Electromagnetic Induction - A APPARATUS 1. Two 225-turn coils 2. Table Galvanometer 3. Rheostat 4. Iron and aluminum rods 5. Large circular loop mounted on board 6. AC ammeter 7. Variac 8. Search coil

### ELECTRICITY & ELECTROMAGNETISM TRANSFORMERS + ETC

Circuitry, Formulas & Electricity Ch5 Bushong RT 244 12 Lect # 3 1 RT 244 WEEK 10 rev 2012 2 LECTURE # 3 ELECTRICITY & ELECTROMAGNETISM TRANSFORMERS + ETC BUSHONG CH. 4 & 5 REF: CARLTONS CH 3, 4 & 5 &

### Magnetic Field and Magnetic Forces

Chapter 27 Magnetic Field and Magnetic Forces PowerPoint Lectures for University Physics, Thirteenth Edition Hugh D. Young and Roger A. Freedman Lectures by Wayne Anderson Goals for Chapter 27 To study

### PHY 212 LAB Magnetic Field As a Function of Current

PHY 212 LAB Magnetic Field As a Function of Current Apparatus DC Power Supply two D batteries one round bulb and socket a long wire 10-Ω resistor set of alligator clilps coil Scotch tape function generator

### 13 ELECTRIC MOTORS. 13.1 Basic Relations

13 ELECTRIC MOTORS Modern underwater vehicles and surface vessels are making increased use of electrical actuators, for all range of tasks including weaponry, control surfaces, and main propulsion. This

### Magnetic Force. For centuries, humans observed strange force. Between iron and special stones called lodestones. Force couldn't be gravity or electric

MAGNETIC FIELD Magnetic Force For centuries, humans observed strange force Between iron and special stones called lodestones Force couldn't be gravity or electric Not enough mass or electric charge to

### Magnetism. Magnetism. Magnetic Fields and Magnetic Domains. Magnetic Fields and Magnetic Domains. Creating and Destroying a Magnet

Magnetism Magnetism Opposite poles attract and likes repel Opposite poles attract and likes repel Like electric force, but magnetic poles always come in pairs (North, South) Like electric force, but magnetic

### S E C T I O N O N E : I N T R O D U C T I O N

S E C T I O N O N E : I N T R O D U C T I O N What you will learn: What electricity is What an electrical current is How electricity is created How electricity is used to perform useful tasks The physical