# Chapter 3: Electricity

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 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 Section 3.4: To discuss the transmission of electricity Section 3.5: To calculate the cost of using electricity 3.1 Electric Charge, Voltage, and Energy Electric Charge The world around us is full of electric charge. Evidence for the existence of electric charge comes from the electric forces between charged objects. Because electric charges on two adjacent objects can cause the objects to move, we conclude that a force must exist between the electric charges. An electric force can move charged objects closer together (an attractive force) or move them apart (a repulsive force). Since electric forces can move charged objects together or apart, we conclude that two opposite types of electric charge must exist. We rarely notice electric charge because most objects contain equal amounts of these two opposite types of electric charge, which cancel one another. A charged object results when a quantity of one type of charge is separated from an equal quantity of the opposite type of charge. The sum of equal quantities of opposite charge is zero. For this reason, the two types of electric charge are called positive charge (+) and negative charge ( ). Objects with equal numbers of positive and negative charge have a total net charge of zero and are electrically neutral. Objects with more positive than negative charge have a net positive charge, and objects with more negative than positive charge have a net negative charge. Charge is measured in units of coulombs (coul). We will use the variable Q to represent charge. Electrical Potential Energy and Voltage Chapter 2 defined work as the product of the force applied to an object times the distance that force caused the object to move: W = F x D. If we ignore wasted energy, the joules of energy required to do this work is equal to the joules of work done. Work and energy are likewise xx in electric charge. When the attractive electric force between positive and negative charges pulls charge together, work must be done against this attractive force to separate the charges. When separated charges are allowed to come back together, we can get work back out. On the other hand, since two positive charges or two negative charges repel one another, we must do work against this repulsive electric force to bring the charges together. We can get work out as the two charges move apart. 24

2 Electrical potential energy is described in terms of charge, Q, and voltage, V, rather than in terms of force times distance. The energy per charge is called the voltage. Voltage is measured in units of volts (V), with 1 volt = 1 joule of energy per 1 coulomb of charge. Voltage is the ratio E pot /Q, that is, voltage is the potential energy per unit of charge as shown in Equation 3.1. E pot Q V (Equation 3.1) where E pot = the electrical potential energy (in joules) (Example 3.1) Q = the charge (in coulombs) V = the voltage (in volts) Electric charge is placed on a metal surface. How much electrical potential energy do 2 x 10 9 coulombs of electric charge have when maintained at a voltage of 2,000 volts? E pot = Q V = 2 x 10 9 coul x 2,000 V = 4 x 10 6 joules 3.2 Electric Current Moving Electric Charge Produces Electric Current When separated electric charge flows through conducting material, the moving charge constitutes an electric current in the conductor. Electric current usually consists of flowing electrons, which can move freely in a conducting material. The amount of electric current is the rate at which charge Q flows past a given point in the conductor. Since charge is measured in coulombs, current I is measured in units of coulombs per second. One coulomb per second is called one ampere (amp). The greater the amount of charge that flows, the larger the electric current. We can express this definition of current with the equation: or Current = Amount of Charge moved Elapsed Time Q I (Equation 3.2) t with I = current (in amperes) Q = charge (in coulombs) t = time elapsed (in seconds) 25

3 (Example 3.2) How much charge must flow to provide a current of 10 amps for 20 seconds? Solve equation 3.2 for Q by multiplying both sides by t and canceling: t Q t I t 10 amps x 20 sec = 200 coul Concept Check 3.1 a) How much current is present if 10 coulombs of charge flow through a conductor every 5 seconds? b) How long must a 5 amp current flow to provide 200 coul of charge? 3.3 Generating Electricity Moving Electric Charges and Magnetic Fields When an electric charge, such as an electron, moves, the charge is surrounded by a magnetic field. The magnetic field produced by an electric current can exert a force and do work on nearby permanent magnets or on other moving electric charges. Likewise, a nearby magnetic field can do work on a current-carrying wire. But an additional effect also occurs a changing magnetic field can produce a current in a nearby conductor such as a piece of metal or a wire that is part of a closed or complete circuit. The changing magnetic field can be produced by moving a magnet or by moving the conductor. The process of generating a current in a conductor is known as inducing a current. In class, we induce a current by moving a magnet into and out of a coil of wire. Moving the magnet into the coil induces a current in one direction in the wire. When the magnet stops moving, the current stops flowing. Pulling the magnet out of the coil produces a current flowing in the opposite direction. To produce this current, only the relative motion of the coil and wire is important the same current is induced whether the coil moves or the magnet moves. Electric Generating Plants The principle that a magnet moving with respect to a wire induces a current in the wire is used in power plants to generate electricity. Generators use magnets and coils of wire to convert kinetic energy into electrical energy. Electric generating plants convert the kinetic energy of rotating magnets into electrical energy by spinning large magnets near coils of conducting wire. To rotate the magnets, generating plants use 26

4 kinetic energy from the sources described below to turn the blades of turbines. Turbines are wheels with blades attached, similar in principle to waterwheels. A shaft attached to the rotating turbine causes the magnets to spin. The most common mechanism for turning turbines is steam pressure. In steam generating plants, water is heated in a closed container. As the water changes to steam, the volume and pressure increase. The steam exerts pressure on the turbine blades, turning them. In many generating plants, water is heated by burning coal, oil, natural gas, or other fuels. In nuclear power plants, water is heated by the thermal energy that results from reactions in radioactive fuels. Fig. 3.1 Turbine In hydroelectric plants, falling water rotates the turbines. The gravitational potential energy of the water is converted into kinetic energy of motion as the water falls and turns the turbines. In addition to the many hydroelectric power plants built along rivers, a tidal powered generating plant along the ocean shore can use tides to turn turbines. In tidal plants, water flows in during high tide and is trapped behind gates. As the tide recedes, the trapped water is left at a higher level than the surrounding ocean. The trapped water returning to the ocean spills over the turbines, turning them. Wind turbines use the kinetic energy of moving air molecules to spin large blades that are attached to a turbine. Wind turbines are most effective when placed in a near constant source of wind, such as along the shore of large bodies of water or on flat plains. 3.4 Transmitting Electricity Joule Heating As electric current moves through wires, electrons collide with atoms of the wire material and some electrical energy is converted into thermal energy. Conversion of electrical energy into thermal energy in a resistor is known as joule heating. Unless the purpose of transmitting current is to generate heat in a wire, such as in a toaster s filament, this thermal energy is wasted. The watts of joule heating power are the product of the current squared times the resistance of the wire. Resistance is the ability of a material to resist the flow of electric current. Resistance is measured in units of ohms ( ). (Equation 3.3) P joule = I 2 R with P joule = power (in watts) I = current (in amperes) R = resistance (in ohms) 27

5 Joule heating in power transmission lines represents both a waste of energy resources and a loss of revenue for the power generating company. Even a voltage drop of only 18 volts between the generating plant and the user represents a large amount of power waste from joule heating. Example 3.3 calculates the amount of wasted power. (Example 3.3) How much power would be wasted as joule heating of the transmission wires if 1.67 x 10 6 amps of current was transmitted with the very small resistance of 1.1 x 10-5 ohms? P joule = I 2 R = (1.67 x 10 6 amps) 2 x (1.1 x 10-5 ohms) = (2.79 x amps 2 ) x (1.1 x 10-5 ohms) = 3.1 x 10 7 watts As shown in Example 3.3, transmitting large amounts of current even at very low resistance would wastes large amounts of power as joule heating of the wires. Fortunately, there is another alternative power transmission at high voltages. Transformers One way to reduce the amount of current in transmission wires is to increase the voltage of that current. Power is directly proportional to the product of current and voltage as shown in Equation 3.4. A higher voltage results in a smaller current for a given amount of power transmitted. (Equation 3.4) P = I V with P = power (in watts) I = current (in amperes) V = voltage (in volts) Transformers make it possible to transmit electricity at a higher voltage by changing the voltage of the electric current. The purpose of a transformer is to trade high voltage for low current or low voltage for high current. From Equation 3.4, we see that as the voltage is increased, the current must decrease to provide the same power. Likewise, if the voltage is decreased, the current increases. Step-up transformers increase voltage and decrease current for long distance transmission. While high voltage reduces joule heating, it poses a safety hazard for consumers. Step-down transformers are used to decrease voltages to safe levels at the point of use of the electricity. 28

6 Step-down transformers reduce the voltage of transmitted power in stages to progressively lower voltages. Power is transmitted over long distances at up to 700,000 volts. Over shorter distances or to small towns with low power requirements, power is transmitted at 25,000 volts. Power lines along city streets typically operate at about 2,000 volts. Finally, a transformer about the size of a garbage can, often located on a utility pole, reduces the voltage for household use. Households are normally supplied 240 volts, which is delivered in such a way as to provide 120 volts to regular outlets and 240 volts to outlets for devices that require more power, such as electric stoves, water heaters, and clothes dryers. (Example 3.5) If a power company transmits electricity at 500,000 volts (5 x 10 5 V) rather than 120 volts, how much current would be needed to provide 200 megawatts of power (2 x 10 8 watts) to a city? Solve P = I V for I by dividing both sides by V and canceling: P V I 2 x x 10 5 watts volts 400 amps Just 400 amps of current could supply 200 megawatts of power when transmitted at a high voltage, compared to the 2.79 x amps of current required to transmit at 120 volts in Example 3.4. Transmitting at high voltage and low current greatly reduces the power wasted as joule heating of the wires. Transformers make it possible to transmit electricity at high voltages, then step the electricity down to lower voltages that are safer for consumer use. Concept Check 3.2 a) A 400 amp current is transmitted through wires with a resistance of 0.8 ohms for every mile of wire. How much power is wasted as joule heating of a transmission wire 200 miles in length? b) If 200 megawatts (2 x 10 8 watts) is the total power input, what is the efficiency of the transmission process? 29

7 3.5 Cost of Electricity Power Measurements and Requirements Power companies provide electrical energy, or electricity, and charge for it in units of kilowatt-hours (kwh). To measure the electrical energy supplied to consumers, power companies use kilowatt-hour meters attached to residences and businesses. The meter is a small electric motor with a rotating disc. Because the rotation speed of the disc is proportional to the power being used at the time, electricity can be measured by the number of rotations of the disc. The measurement of electricity may be shown by a digital display or by an analog display with rotating pointers on dials. The difference between the current month's dial reading and previous month's reading measures the total energy provided, which is used to determine the electric bill. To calculate the cost of electricity from an electric bill, we must know how many kilowatts of electric power were used and for how many hours. Power is the energy transferred or work done divided by the time required, as shown in Equation 3.5. with P = E = W t t P = power (in watts) E = energy transferred (in joules) W = work done (in joules) t = time elapsed (in seconds) (Equation 3.5) From Equation 3.5, you see that the faster energy is transferred or work is done, the greater the power required. (Example 3.6) How many kilowatt-hours (kwh) of energy are required to operate a 1,000 watt electric heater for 2 hours? Find the energy used by an appliance by solving equation 3.5 for the energy requirement, E. P E t or E P t E = 1,000 watts x 2 hours = 2,000 watt-hours. Use a ratio to convert from watts to kilowatts: 2,000 watt-hours x 1 kw = 2 kilowatt-hours = 2 kwh 1,000 watts 30

8 The total kilowatt-hours of energy used during a month is the sum of the power requirement of each appliance multiplied by the hours that appliance operated. (Example 3.7) How many kilowatt-hours of energy are used when a 100 watt light bulb burns for 7 hours, a 1,000 watt hair dryer operates for 15 minutes, and a 1,500 watt electric heater operates for ½ hour? Light bulb: 1kilowatt 100 watts x x 7 hours 1,000 watts 0.70 kilowatt hours Dryer: 1kilowatt 1 hour 1,000 watts x x 15 min x 1,000 watts 60 min 0.25 kilowatt hours Heater: 1 kilowatt 1 hour 1,500 watts x x 30 min x 1,000 watts 60 min 0.75 kilowatt hours The total energy used is 0.70 kwh kwh kwh = 1.7 kilowatt-hours. (Example 3.8) If the power company charges \$0.10 per kilowatt-hour of energy, how much would you pay for the energy used by the light bulb, hair dryer, and heater in Example 3.7? Energy Cost = number of kwh used x cost per kwh \$ kilowatt hours x 1 kilowatt hour \$0.17 Concept Check 3.3 a) How many kilowatt-hours are required to use a 600 watt oven for 45 minutes? b) If electricity costs \$0.10 per kilowatt-hour, how much would you pay to operate the oven for 45 minutes? 31

9 Table 3.1: Metric and English Units and Their Symbols Quantity Symbol Metric Units Metric Unit Abbreviation English Unit English Unit Abbrev. Force F newton N (1 N = 1 kg m/s 2 ) pound lb Energy E joule J (1 J = 1 kg m 2 /s 2 ) foot-pound ft-lb Work W joule J foot-pound ft-lb Power P watt W (1 W = 1 J/s) horsepower hp (1 hp = 550 ft-lb/s) 32

10 Chapter 3 Summary 3.1 Electric charge Q is measured in coulombs. The voltage V is the energy per charge. The electrical potential energy of charge Epot = Q V 3.2: Moving electric charge is electric current I. Current is measured in units of amperes or amps. Since current is the rate of flow of charge, I = Q/t 3.3: Electric current is generated, or induced, when magnets and coils of wire move relative to one another. In power generating plants, kinetic energy from steam, flowing water, or wind turns turbines. The moving turbines spin magnets near coils of wire. 3.4: Electric generating plants are often located far from heavily populated areas, thus the electricity they generate must be transmitted long distances to its point of use. To transmit electricity to consumers, the electricity is transmitted at high voltage to minimize the power wasted as joule heating of the transmission wires. Joule heating (P joule = I 2 R) occurs when some electrical energy transmitted through wires is wasted as thermal energy heating the wires. Transformers trade current and voltage, while keeping the power nearly constant. (P = I V). Step-up transformers are used to reduce the current and increase the voltage for efficient long distance transmission of electricity. Less current transmitted reduces power wasted as joule heating. Near the point of electricity consumption, step-down transformers reduce the voltage and increase the current for safer use of electricity. 3.5: Power is the rate at which work is done or energy is transferred. P = W/t or P = E/t Power is measured in joules/second, or watts, in the metric system and in footpounds/second, or horsepower, in the English system. Electrical energy provided to homes is measured and billed to consumers in units of kilowatt-hours. To find the cost of electricity for using an appliance: 1) Convert watts to kilowatts, by dividing watts by 1,000. 2) Find the total time of use in hours. 3) Multiply kilowatts times hours to find the total kwh. 4) Multiply kwh by the cost per kwh. 33

11 Solutions to Chapter 3 Concept Checks 3.1 a) I = Q = 10 coul. = 2 amps t 5 sec b) I = Q or t = Q = 200 coul. = 40 sec t I 5 amps 3.2 a) P joule = I 2 R = (400 amps) 2 x 0.8 ohms = 128,000 watts/mile 128,000 watts/mile x 200 miles = 25,600,000 watts = 2.56 x 10 7 watts b) 2 x 10 8 watts = total power input total power input = useful power out + wasted power out useful power out = total power input wasted power out useful power out =2 x x 10 7 = 2 x x 10 8 = 1.74 x 10 8 (Note that 2.56 x 10 7 was converted to x Adding or subtracting numbers in scientific notation requires each number to have the same power of ten.) Efficiency = useful power out = 1.74 x 10 8 watts = 0.87 = 87% total power in 2 x 10 8 watts 3.3 a) E = P t = 600 watts x 0.75 hours = 450 watt-hours. Use a ratio to convert from watts to kilowatts: 450 watt-hours x 1 kw = 0.45 kilowatt-hours = 0.45 kwh 1,000 watts b) 0.45 kwh x \$0.10 = \$0.045 kwh 34

### Electrical Power. How do you calculate electrical power? 14.3

. Name: Date: Electrical Power 14.3 How do you calculate electrical power? In this skill sheet you will review the relationship between electrical power and Ohm s law. As you work through the problems,

### Objectives 316 CHAPTER 6 POWER

Objectives Explain the relationship between power, current, and voltage in electrical systems. Explain the relationship between power, current, and resistance in electrical systems. Calculate energy usage

### Chapter 13 Electric Circuits

Chapter 13 Electric Circuits What is Electric Current? How does it resemble the flow of water in a pipe? Can you get a flashlight bulb to light, with a battery and a single wire? Electric Circuits and

### 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

### 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,

### 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

### 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

### 4 Electrical Quantities and Ohm s Law

Ch a pt er 4 Electrical Quantities and Ohm s Law Learning Outcomes Define electric current, voltage, resistance, power, and energy, and list the unit of measurement of each. Identify the essential parts

### How do you measure voltage and current in electric circuits? Materials

20A Electricity How do you measure voltage and current in electric circuits? Electricity Investigation 20A We use electricity every day, nearly every minute! In this Investigation you will build circuits

### Chapter 5. Electrical Energy

Chapter 5 Electrical Energy Our modern technological society is largely defined by our widespread use of electrical energy. Electricity provides us with light, heat, refrigeration, communication, elevators,

### Direction of current flow. Heat produced in a resistor. Heat produced in a resistor. L 27 Electricity and Magnetism [4]

L 27 Electricity and Magnetism [4] simple electrical circuits direct current DC Alternating current (AC) vs direct current (DC) electric power distribution household electricity household wiring GFIC s

### IV. POWER. P = W t. = E t. where W is the work done, t is the time required to do the work, and E is the energy used. 1 horsepower = 1 hp = 550

IV. POWER A. INTRODUCTION Power is the rate at which work is done. Work involves a force or force-like quantity acting on object and causing its displacement in the direction of the force. The time required

### Preview of Period 13: Electrical Resistance and Joule Heating

Preview of Period 13: Electrical Resistance and Joule Heating 13.1 Electrical Resistance of a Wire What does the resistance of a wire depend upon? 13.2 Resistance and Joule Heating What effect does resistance

### I = V/r P = VI. I = P/V = 100 W / 6 V = 16.66 amps. What would happen if you use a 12-volt battery and a 12-volt light bulb to get 100 watts of power?

Volts, Amps and Ohms Measuring Electricity The three most basic units in electricity are voltage (V), current (I) and resistance (r). Voltage is measured in volts, current is measured in amps and resistance

### ELECTRICITY - A Secondary Energy Source

ELECTRICITY - A Secondary Energy Source A Secondary Source The Science of Electricity How Electricity is Generated/Made The Transformer - Moving Electricity Measuring Electricity energy calculator links

### Chapter 2: Forms of Energy

Chapter 2: Forms of Energy Goals of Period 2 Section 2.1: To describe the forms of energy Section 2.2: To illustrate conversions from one form of energy to another Section 2.3 To describe energy storage

### Henry Lin, Department of Electrical and Computer Engineering, California State University, Bakersfield Lecture 3 (Electric Circuits) July 16 th, 2013

Henry Lin, Department of Electrical and Computer Engineering, California State University, Bakersfield Lecture 3 (Electric Circuits) July 16 th, 2013 1 What is an electrical circuit? An electrical network

### Quiz: What is the voltage difference across the 25- resistance?

Quiz: What is the voltage difference across the 25- resistance? a) 0.1 V b) 2.5 V c) 6 V d) 25 V e) 60 V since I 25 I series : V 25 I series R 25 0.1 A 25 2.5 V In a parallel circuit, there are points

### Coulomb's Law. Two like charges of 1 Coulomb placed 1 meter apart repel each other with a force of 9 x 10 9 Newtons

Electricity Electricity is a force much like gravity but many times more powerful. Unlike gravity, electrical forces can be attractive or repulsive. Gravity has only one type of mass. Electricity has two

### Chapter 2: Forms of Energy

Chapter 2: Forms of Energy Goals of Period 2 Section 2.1: To describe the forms of energy Section 2.2: To illustrate conversions from one form of energy to another Section 2.3: To define the efficiency

### Section 5. Electric Power: Load Limit. What Do You See? What Do You Think? Investigate. Learning Outcomes

Section 5 Electric Power: Load Limit What Do You See? Learning Outcomes In this section, you will Define power, insulator, and conductor. Use the equation for power, P = IV. Calculate the power limit of

### Topic Seven: P1.3.1 Transferring electrical energy

Topic Seven: P1.3.1 Transferring electrical energy Electrical Devices Electrical energy is very versatile. It can be transformed into most other kinds of energy: Light bulb Electric heater Electric motor

### Power Ranger: Monitoring Electrical Appliances

Power Ranger: Monitoring Electrical Appliances Outcomes: 1. Understand how to use a power monitoring meter to measure line voltage, current, and power consumption. 2. Understand the difference between

### 1&2) -Have the students split into groups of 4. Each of them should go around and explain the answers they found for the pre-visit activity.

We use electricity to power things that we use every day from our lights to our refrigerators. In order for the students to get the most out of the program when they visit Macalester, I thought it would

### Electric Currents. Electric Potential Energy 11/23/16. Topic 5.1 Electric potential difference, current and resistance

Electric Currents Topic 5.1 Electric potential difference, current and resistance Electric Potential Energy l If you want to move a charge closer to a charged sphere you have to push against the repulsive

### 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

### 1) ASSOCIATE ELEMENTARY PARTICLES WITH THEIR ELECTRICAL CHARGE

Name Date STUDY GUIDE CHAPTER 5 ELECTRICITY AND MAGNETISM 1) ASSOCIATE ELEMENTARY PARTICLES WITH THEIR ELECTRICAL CHARGE Scientists now know that an atom is composed of even smaller particles of matter:

### Current and resistance

Current and resistance Electrical resistance Voltage can be thought of as the pressure pushing charges along a conductor, while the electrical resistance of a conductor is a measure of how difficult it

### Fundamentals of Direct Current Circuits

Fundamentals of Direct Current Circuits Course No: E06-001 Credit: 6 PDH A. Bhatia Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774

### Electricity. Electricity: The Mysterious Force. 32 Intermediate Energy Infobook CARBON ATOM SEVERAL COMMON ELEMENTS

Electricity: The Mysterious Force What exactly is the mysterious force we call electricity? It is simply moving electrons. And what exactly are electrons? They are tiny particles found in atoms. Everything

### 7. What is the current in a circuit if 15 coulombs of electric charge move past a given point in 3 seconds? (1) 5 A (3) 18 A (2) 12 A (4) 45 A

1. Compared to the number of free electrons in a conductor, the number of free electrons in an insulator of the same volume is less the same greater 2. Most metals are good electrical conductors because

### Chapter 17 Study Questions Name: Class:

Chapter 17 Study Questions Name: Class: Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. If two charges repel each other, the two charges

### 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

### 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

### Concept Review. Physics 1

Concept Review Physics 1 Speed and Velocity Speed is a measure of how much distance is covered divided by the time it takes. Sometimes it is referred to as the rate of motion. Common units for speed or

### Physics Worksheet Electric Current Section: Name:

Do Now: Water Flow vs. Electric Current Models: f an electric circuit consists of wires, a battery and a light bulb, please compare the water flow in the following picture to the electric current in a

### Temperature coefficient of resistivity

Temperature coefficient of resistivity ρ slope = α ρ = ρ o [ 1+ α(t To )] R = R o [1+ α(t T o )] T T 0 = reference temperature α = temperature coefficient of resistivity, units of (ºC) -1 For Ag, Cu, Au,

### HYDROPOWER Basics Glossary of Terms

Alternating current (AC) Electric current that reverses direction many times per second. Ampere A measure of electric current (similar to describing water volume in cubic feet per second). Ancillary services

### UNIT 1 GCSE PHYSICS 2011 FXA. 1.3.1 Transferring Electrical Energy APPLIANCE USEFUL ENERGY NON-USEFUL ENERGY

UNIT 1 Examples of energy transformations that everyday electrical devices bring about. APPLIANCE USEFUL ENERGY NON-USEFUL ENERGY 40 The amount of electrical energy a device transforms depends on how long

### 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

### 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

### Ch. 20 Electric Circuits

Ch. 0 Electric Circuits 0. Electromotive Force Every electronic device depends on circuits. Electrical energy is transferred from a power source, such as a battery, to a device, say a light bulb. Conducting

### Energy transfers in appliances - cost and power

Energy transfers in appliances - cost and power 9 minutes 93 marks Page of 37 Q. The diagrams in List A show three electrical appliances. Each appliance is designed to transfer electrical energy. Draw

### f. The current at location A is equal to the current at location B. e. The current at location B is greater than the current at location E.

1. Answer: The current outside the branches of a combination circuit is everywhere the same. The current inside of the branches is always less than that outside of the branches. When comparing the current

### Coulomb s Law. F = k q 1q 2. k = x 10 9 N m 2 /C 2

Electricity Electricityisaforcemuchlikegravitybutmillionsoftimemorepowerful. Unlike gravity, electricity can be attractive and repulsive. There are two types of electric charge which are labeled positive

### General Physical Science

General Physical Science Chapter 4 Work and Energy Work The work done by a constant force F acting upon an object is the product of the magnitude of the force (or component of the force) and the parallel

### s_5xut Page 1 Physics Samples

Physics Samples E&M Unit 1. Two metal spheres having charges of +4.0 x 10 6 coulomb and +2.0 x 10 5 coulomb, respectively, are brought into contact and then separated. After separation, the charge on each

### A kilowatt-hour (kwh) is a unit for measuring energy. It is, as its name suggests, one kilowatt of power used over a period of one hour.

How Much Electricity Does a Light Bulb Use and What will it Cost Me? We (the Village of Paw Paw) are often asked How do I know how much electricity a home appliance or device is using and what is the charge

### S15--Physics current and Circuit PRACTICE

Name: Class: Date: ID: A S5--Physics current and Circuit PRACTICE Multiple Choice Identify the choice that best completes the statement or answers the question.. Three resistors, with values of 2.0, 4.0

### Forms of Energy: Multiple Transformations : Teacher Notes

Forms of Energy: Multiple Transformations : Teacher Notes Introduction The focus of the investigation is to further define energy and realize that chains of energy transformations can occur. The VoltageCurrent,

### Series and Parallel Circuits

Series and Parallel Circuits Components in a circuit can be connected in series or parallel. A series arrangement of components is where they are inline with each other, i.e. connected end-to-end. A parallel

### MC Electricity Resistors Review

2. In the circuit shown above, what is the value of the potential difference between points X and Y if the 6 volt battery has no internal resistance? (A) 1 V (B) 2 V (C) 3 V (D) 4 V (E) 6V 8. The circuit

### Forms of Energy. Freshman Seminar

Forms of Energy Freshman Seminar Energy Energy The ability & capacity to do work Energy can take many different forms Energy can be quantified Law of Conservation of energy In any change from one form

### PHYS-2020: General Physics II Course Lecture Notes Section III

PHYS-2020: General Physics Course Lecture Notes Section Dr. Donald G. Luttermoser East Tennessee State University Edition 4.0 Abstract These class notes are designed for use of the instructor and students

### Electrical Principles, Terminology, and Safety. Instructional Materials Service Texas A&M University

Electrical Principles, Terminology, and Safety Instructional Materials Service Texas A&M University Definition of Electricity Layman s Definition: a form of energy that can be converted to light, heat,

1 ANSWERS to CIRCUITS 1. The speed with which electrons move through a copper wire is typically 10-4 m s -1. a. Explain why is it that the electrons cannot travel faster in the conductor? b. Explain why

### National 4 Summary Notes

North Berwick High School Department of Physics National 4 Summary Notes Unit 3 Electricity and Energy Physics N4 Unit 1: Pupil Notes Page 1 of 22 Section 1: Generation of Electricity What is electricity?

### Energy is the basic necessity for the economic

CHAPTER 1 Introduction 1.1 Importance of Electrical Energy 1.2 Generation of Electrical Energy 1.3 Sources of Energy 1.4 Comparison of Energy Sources 1.5 Units of Energy 1.6 Relationship Among Energy Units

### Energy The Word vs. The Physics Concept

ENERGY Energy The Word vs. The Physics Concept The word energy is used loosely As a commodity I paid my energy bill today Does energy come through pipes like water? As a mood or behavior He played with

### Electrical Charge: a type of energy that comes from the flow of charged particles; it allows electrical devices to function.

Unit E: Electrical Applications Chapter 11: Electrical Energy 11.1: Generating Electricity pg. 420 Key Concepts: 1. Electrical energy is generated using a variety of technologies. 2. Electrical energy

### 60 kg 10 m/s 3000 J b W P 1500 W

Final Exam Review Activity hysics 100 December 15, 016 rofessor Menningen Section I. Answer True (+) or False (O) Name: 1. Molecules at 00 ºC K have twice the average kinetic energy than molecules at 100

### COMPONENT SYMBOL COMPONENT SYMBOL

DUNFERMLINE HIGH SCHOOL NATIONAL PHYSICS HOMEWORK 01 Symbols and Plug EQUATIONS: Question 1 5 Marks Copy and complete the following table. COMPONENT SYMBOL COMPONENT SYMBOL wire switch cell battery bulb

### Work and Energy. Work = Force Distance. Work increases the energy of an object. Energy can be converted back to work.

Work and Energy Ch. 6 Work = Force Distance Work increases the energy of an object. Energy can be converted back to work. Therefore, energy and work have the same unit: Newton meter = Nm Energy per gram,

### OHM S LAW 05 AUGUST 2014

OHM S LAW 05 AUGUST 2014 In this lesson, we: Current Lesson Description Revise the definitions of current, potential difference and emf Explore Ohm s law Identify the characteristics of ohmic and non-ohmic

### Science 9 Unit D Electrical Principles Topic 3.0

Science 9 Unit D Electrical Principles Topic 3.0 Energy is all around us in many different forms light from lamps, sound from stereos, heat from furnaces and stoves. Yet we rarely think about how much

### 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

### Basic Electrical Theory

Basic Electrical Theory Power Principles and Phase Angle PJM State & Member Training Dept. PJM 2014 10/24/2013 Objectives At the end of this presentation the learner will be able to; Identify the characteristics

### In science, energy is the ability to do work. Work is done when a force causes an

What is energy? In science, energy is the ability to do work. Work is done when a force causes an object to move in the direction of the force. Energy is expressed in units of joules (J). A joule is calculated

### STEM 2 3: The Basics of Energy, Electricity, and Water Jigsaw

STEM 2 3: The Basics of Energy, Electricity, and Water Jigsaw Objective To increase understanding of forms of energy, sources of energy, atomic structure, electricity, magnetism, electricity generation,

### Energy and Power Energy

Energy and Power Energy Energy is the capacity to change a physical situation. When we say we are full of energy we mean that we could do a lot of physical thing.s Energy can neither be made nor destroyed

### ( ) where W is work, f(x) is force as a function of distance, and x is distance.

Work by Integration 1. Finding the work required to stretch a spring 2. Finding the work required to wind a wire around a drum 3. Finding the work required to pump liquid from a tank 4. Finding the work

### Energy and Society. Professor Ani Aprahamian

Energy and Society Professor Ani Aprahamian Wednesday, September 14th Nieuwland Science Hall 123; 6 pm - 7pm Dr. Peter Burns - "Nuclear Energy: Past Mistakes, Current Challenges, Future Prospects" Thursday,

### ELECTRICITY (E) So, what is this mysterious stuff that we call E? Where does it come from? Where does it go and why is it

ELECTRICITY (E) Electricity how it works, how we measure and pay for it. INTRODUCTION: HOW ELECTRICITY WORKS: E completely surrounds us. Modern life would be rather primitive without it. A few examples

### What is the direction of a compass needle placed at point A?

SAMPLE QUIZ: COVERAGE OHM S LAW CIRCUIT ANALYSIS RESISTANCE ELECTRICAL POWER MAGNETISM AND ELECTROMAGNETISM MAGNETISM: 1. In order to produce a magnetic field, an electric charge must be 1. stationary

### The Environmental Cost of Using Electricity

Calculating Energy Costs The watt (W) is a unit of electrical power, which is the rate at which we use energy. We pay the electric company for the use of energy. A kilowatt (kw) is equal to 1000 watts:

### Energy, electricity and magnetism page The diagram below shows an object made from a battery, a nail, and some wire.

Energy, electricity and magnetism page 3 Name: ate: 1. The diagram below shows an object made from a battery, a nail, and some wire. What will happen if you touch a metal paperclip to the nail? A. The

### Science AS90191 Describe Aspects of Physics.

Circuits and components Science AS90191 Describe Aspects of Physics. An electric current is the movement of electrons (negatively charged particles). A circuit is made up of components connected together

### 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

### Electric current II. Except in a superconductor

Electric current Charges in motion: Count positive charges going from left to right Add negative charges going from right to left Subtract all charges moving in the opposite direction Divide by time =>

### Topic 1 Electrical Charges

Topic 1 Electrical Charges 1. When are materials said to be electrically charged? Materials are positively charged if They have an uneven number of protons and electrons 2. How could you produce an electric

### 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

### Chapter 2 Faraday s Miracle

Chapter 2 Faraday s Miracle In this chapter we discuss how electricity generators work. Michael Faraday was the father of electricity generation. Almost 200 years ago, he discovered electromagnetic induction.

### 101 BASICS SERIES LEARNING MODULE 2: FUNDAMENTALS OF ELECTRICITY. Cutler-Hammer

101 BASICS SERIES LEARNING MODULE 2: FUNDAMENTALS OF ELECTRICITY Cutler-Hammer WELCOME Welcome to Module 2, Fundamentals of Electricity. This module will cover the fundamentals of electricity in a practical

### Electric Motors and Generators

Electric Motors and Generators Motors run a tremendous number of devices, from toy trains to refrigerators, from air conditions to cars. What is inside a motor and how do they work? How are motors related

### Gravitational Potential Energy

Gravitational Potential Energy Consider a ball falling from a height of y 0 =h to the floor at height y=0. A net force of gravity has been acting on the ball as it drops. So the total work done on the

### Are You Switched on to Switching Off?

Lesson 2.12 - Power Station to Plug Are You Switched on to Switching Off? Play Animation 1 Play Animation 2 what you will need Lesson 2.12 - Power Station to Plug click for more Key Question: Are You Switched

### Energy Transfer, PE, KE and Efficiency

ENERGY Part of our everyday lives: Energetic people Food that is full of energy High cost of electric energy Risks of nuclear energy Energy: An ability to accomplish change When anything happens in the

### Understanding and Measuring School Electronics

Understanding and Measuring School Electronics MATERIALS NEEDED: 1. 6 energy monitoring devices (note: these can be obtained from a variety of sources, i.e., local hardware stores, internet [average cost

### Power and Power Measurement. ENGR 10 Intro to Engineering College of Engineering San Jose State University

Power and Power Measurement ENGR 10 Intro to Engineering College of Engineering San Jose State University Electricity is a convenient way of transmitting energy by wires Sourcing Energy Energy transmission

### Introduction to Hydroelectric Power. This lesson provides an overview of hydroelectric power (also called

Overview This lesson provides an overview of hydroelectric power (also called hydropower), with an emphasis on low-head and low impact hydropower. Students view an audiovisual presentation, Introduction

### Period 9 Activity Sheet Solutions: Power

Period 9 Activity Sheet Solutions: Power Activity 9.1: How Much Power Do Appliances Require? a) Light Bulbs: Connect the small hand-cranked generator to the 4-bulb tray. Compare how easily the crank turns

### Section B: Electricity

Section B: Electricity We use mains electricity, supplied by power stations, for all kinds of appliances in our homes, so it is very important to know how to use it safely. In this chapter you will learn

### Electricity Review-Sheet

Name: ate: 1. The unit of electrical charge in the MKS system is the. volt. ampere. coulomb. mho 2. Which sketch best represents the charge distribution around a neutral electroscope when a positively

### Two kinds of electrical charges

ELECTRICITY NOTES Two kinds of electrical charges Positive charge Negative charge Electrons are negatively charged Protons are positively charged The forces from positive charges are canceled by forces

### Electric Potential Difference

Name: Electric Potential Difference Read from Lesson 1 of the Current Electricity chapter at The Physics Classroom: http://www.physicsclassroom.com/class/circuits/u9l1a.html http://www.physicsclassroom.com/class/circuits/u9l1b.html

### Student Content Brief Advanced Level

Student Content Brief Advanced Level Electric Circuits Background Information There are a variety of forces acting on the body of the Sea Perch. One important force is pushing electrons through the wires

### Part 1. Part 1. Electric Current. and Direct Current Circuits. Electric Current. Electric Current. Chapter 19. Electric Current

Electric Current Electric Current and Direct Current Circuits Chapter 9 Resistance and Ohm s Law Power in Electric Circuits Direct Current Circuits Combination Circuits Real life is mostly dynamic Part

### What will we learn in this chapter?

Chapter 19: Current, resistance, circuits What will we learn in this chapter? What are currents? Resistance and Ohm s law (no, there are no 3 laws). Circuits and electric power. Resistors in series and