Circuits Review KEY Interpreting Diagrams Use the diagram below to answer the following questions.

Transcription

1 Circuits Review KEY Interpreting Diagrams Use the diagram below to answer the following questions. 1. Look at the arrows which indicate the direction of the flow of electrons. Label the negative and the positive terminals on the battery above. 2. Explain how you knew which terminal was negative and which terminal was positive. Electrons come out of the negative end and into the positive end Series Closed Battery Direct 2 light bulbs 3. Is this a series circuit or a parallel circuit? 4. Is the circuit open or closed? 5. What is the electrical energy source for the circuit? 6. Is the circuit using direct current or alternating current? 7. What device is the load in this circuit? (there are two of them) 8. If one of the lamps in the circuit burns out, what will happen to the other lamp? Also, why does it If one lamp burns out, the other will not work. This is because there is only one path for the electricity to flow. happen? 9. Re-draw the above circuit using common representations for the battery and the bulbs. (Remember that the bulbs are resistors.)

2 Multiple Choice Write the letter of the term or phrase that best completes each statement. 1. Safe electrical cords use a. only conductors. b. only insulators. c. both conductors and insulators. d. neither conductors nor insulators. 2. Electric current can flow only through a. a closed circuit. b. an open circuit. c. a parallel circuit. d. a series circuit. 3. A circuit in which electric charges can follow more than one path is called a a. double circuit. b. multi-circuit. c. series circuit. d. parallel circuit. 4. The energy available to move electric charges is called a. electrical force. b. voltage. c. static electricity. d. resistance. 5. The atomic particle with a negative electric charge is called the a. proton. b. electron. c. neutron. d. nucleus. 6. The kind of electric current generated by power plants is a. either AC or DC. b. DC. c. AC. d. neither AC nor DC. 7. The part of an atom that is free to move is the a. electron. b. proton. c. nucleus. d. neutron.

3 8. In direct current, electric charges a. reverse directions. b. move in one direction. c. vibrate. d. do not move. 9. Of the following materials, the best conductor is a. copper. b. cork. c. wood. d. paper. 10. Electricity can flow easily through all a. plastics. b. gases. c. insulators. d. conductors. 11. An electric circuit is shown below. The accompanying table shows the current measured at different levels of resistance. Resistance Current (Ω) (A) Based on the data shown in the table, what is the voltage drop across the variable resistor? A. 1.5 V B. 6 V C. 9 V D. 12 V 12. Mr. Jenkins constructed a circuit consisting of a variable source, wires, and a resistor. In order to triple the amount of current, how should he change the voltage of the source? A. make the voltage three times larger B. make the voltage one-third as great C. make the voltage nine times larger D. make the voltage one-ninth as great

4 13. What is the voltage in a circuit with a current of 3 Amps and a total resistance of 12 Ω? A V B. 4 V C. 15 V D. 36 V 14. The circuit diagram below shows three resistors, an ammeter, and a battery. How much current flows through the ammeter? A. 1.0 A B. 6.0 A C A D Students in a physics lab are studying the circuit shown in the diagram below. Which of the following options will double the current through the ammeter? A. replacing the battery with a 5 V battery B. adding a 30 Ω resistor in parallel with R C. replacing the resistor with a 30 Ω resistor D. adding a second 60 Ω resistor in series with R 16. A 72 W navigation unit on a commercial aircraft has a 24 V power supply and uses 3 A of electric current. What is the electrical resistance of the navigation unit? A. 4 Ω B. 8 Ω C. 13 Ω D. 22 Ω

5 17. The diagram below shows an incomplete circuit due to a break in the wire at point X. A student is testing materials to see if they conduct electricity. The student places each item shown at position X, making sure the object is in contact with the loose end of each wire. Which item will electricity flow through, causing the bulb to light? Correct answer is D 18. When a light bulb is turned on, energy changes from one form to another. Which of the following best describes this change? A. sound energy to light energy B. nuclear energy to light energy C. electrical energy to light energy D. magnetic energy to light energy 19. Marta has a radio in her room. It requires electricity in order to play. Which of the following is necessary in order for electricity to move from the source to the radio? A. a circuit B. a magnet C. a light bulb D. an insulator

6 20. The figures below show a light bulb connected to a battery in two different ways. When the switch in Figure 1 is closed the bulb will light. A plastic ring is inserted in the circuit as shown in Figure 2. What will happen when the switch is closed in Figure 2? A. The bulb will light just as it did in Figure 1. B. The bulb will be brighter than it was in Figure 1. C. The bulb will light, but will be less bright than it was in Figure 1. D. The bulb will not light at all. MCAS Open Response Question: Look at the objects shown below. Some of these objects are conductors of electricity and some are insulators. a. List all the objects that are conductors. b. List all the objects that are insulators. c. Describe the difference between a conductor of electricity and an insulator of electricity. a. Conductors: paper clip, copper tubing, clothes hanger (if made of metal) b. Insulators: rubber band, glass tubing, clothes hanger (if made of plastic) c. Conductors have loosly bound electrons so they allow electrons to flow through them easily. Insulators have tightly bound electrons so they prevent the flow of electrons through them.

7 Written Response Answer the following questions in complete sentences. 1. Kamaria is hanging a string of decorative lights. When she plugs the lights in, she notices that one light in the string is burned out. The rest of the lights are still lit. Are the lights wired in a series circuit or in a parallel circuit? How do you know? The light are wired in a parallel circuit. I know because one of them stopped working but the others did not. In a parallel circuit, each light bulb has its own path for the electricity to flow. 2. What are the forms of energy involved in a simple circuit? There are four major forms of energy involved. Write two to three sentences discussing the energy transformations that take place. In a simple circuit there are: chemical potential energy, electric energy, light energy, and heat energy. The battery converts chemical potential energy into electric energy. The light bulb converts electric energy into light and heat energy. Problem Solving: Use your MCAS formula sheet to help you. SHOW ALL WORK. 1. A hairdryer is plugged into a 120 Volt outlet and draws 30 Amps of Current. What is the Power rating of the hairdryer? V = 120 V P = I V I = 30 A P = (120 V)(30 A) P? P = 3600 W 2. How much current is flowing through the ammeter? 9 volts 3 ohms A V = 9 V I = V/R R = 3 ohms I = (9 V)/(3 ohms) I? I = 3 A # If#one#lamp#burns#out,#the#other#will#not#work.#This#is# because#there#is#only#one#path#for#the#electricity#to#flow.#

8 Key Term Review: Match each term in Column B with its definition in Column A. Write the correct letter in the space provided. Each term is used once and only once. Column A 1. D 1. atomic particle with a negative electric charge 2. I 2. material through which electric charges do not flow easily 3. J 3. flow of electric charges through a conductor 4. L 4. switch that opens a circuit if too much current is flowing 5. F 5. circuit in which electric current follows only one path 6. material through which electric charges flow easily 6. N 7. atomic particle with a positive electric charge 7. A 8. current in which electrons change direction at a regular rate 8. B 9. circuit in which electric current can follow more than 9. C one path 10. R 10. the rate at which work is done. 11. O 11. unit used to measure resistance 12. K 12. energy available to move electric charges through a wire 13.E 13. path that an electric current follows 14. P 14. the units used for power 15. opposition to the flow of electric current 15. G 16. unit used to measure electric current 16. M 17. the units used for energy 17. Q 18. unit used to measure voltage 18. K Interpreting Diagrams Use the diagram below to answer the following questions. Column B a. proton b. alternating current c. parallel circuit d. electron e. electric circuit f. series circuit g. resistance h. volt i. insulator j. electric current k. voltage l. circuit breaker m. ampere n. conductor o. ohm p. Watt q. Joule r. power Filament 1. Trace the path that a current takes through the bulb. 2. Label the filament. 3. Explain why the filament glows when current flows through it: It glows because electrons are passing through it making it heat up and glow.

9 Drawing and Explaining Diagrams : Use circuit diagram symbols for the following questions. 1. SHORT CIRCUITS: a. Draw a complete circuit that includes one battery and one bulb. Then add wire(s) to short circuit the bulb. NO b. Does a short circuited bulb light? Why or why not? The electrons must come into the light bulb and out of the light bulb through 2 different places (side and bottom) for the light bulb to work. A short circuit connects the battery to itself without including the load (light bulb) 2. SERIES CIRCUITS: a. Draw a circuit that has two batteries and three bulbs in series. b. One bulb is broken. Do the other bulbs light? NO c. You add a fourth bulb in series. What happens to the brightness of the bulbs? As you add another light bulb, the bringhtness goes down. This is because more light bulbs increases the total resistance of the circuit which decreases the current drawn out of the battery. 3. PARALLEL CIRCUITS: a. Draw a circuit that has one battery and two bulbs in parallel. b. One bulb is broken. Does the other bulb light? YES c. You add a second battery. What happens to the brightness of the bulbs? As you add another light bulb, the bringhtness stays the same. This is because more light bulbs decreases the total resistance of the circuit which increases the current drawn out of the battery.