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Unit 5 Practice Test

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                             Electricity and Magnetism Practice Test
1. An ampere is a…
a) Unit of resistance b) Unit of current      c) Unit of charge      d) Unit of voltage

2. A microwave has a resistance of 30 ohms. How much current will pass through the microwave when
it is plugged in to a 120-V electrical outlet?
a) 90 A                 b) 40 A                c) 4 A         d) 0.25 A

3. What is the resistance of the circuit in the diagram shown to the right?
a) 240 Ω
b) 15 Ω
c) 30 Ω
d) 0.067 Ω


4. If 0.5 amps of current pass through the 12-ohm resistor in the circuit below, what is the voltage of the
battery?
a) 6 V
b) 24 V
c) 60 V
d) 2.4 V




5. A 60-watt light bulb is plugged in to a 240-V electrical outlet. How much current passes through the
light bulb?
a) 4 A                b) 40 A                c) 0.25 A               d) 2.5 A

6. Which electrical device is used to amplify the current in a circuit?
a) Capacitor          b) Transistor          c) Superconductor        d) Resistor

7. If an electron is found near a positively-charged object, the two will ________________.
a) Attract              b) Repel               c) Neither

8. The Earth is surrounded by a magnetic field. This field is able to deflect __________ coming from the
Sun.
a) Light              b) X-rays             c) Charged particles d) Gas particles

9. What is the direction of the magnetic field in the coil shown to the right?
a) Up
b) Down
c) Left
d) Right

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10. When a magnet is moved into and out of a coil of wire, it will induce a(n) ______________ in the
wire.
a) Electric field   b) Magnet             c) Current                d) Resistor

11. A plasma is a gas that has become ___________________.
a) Magnetized         b) Electrified       c) Induced                   d) Ionized

12. The symbol used to represent resistance in a schematic diagram is…
a) Two straight lines b) One straight line c) A zigzag line       d) A circle

13. A capacitor is used in a circuit to…
a) Control the amount of current                b) Store electric charge
c) Amplify the current                          d) Decrease the resistance

14. In Portugal, the voltage of the electrical outlets is 220 V (here in the US it is 120 V). If you were to
plug in a light bulb in Portugal with 240  of resistance, how much current would pass through the bulb?
a) 2 A                  b) 0.92 A              c) 0.5 A                d) 1.1 A

15. What is the voltage of the battery in the circuit shown to the right?
a) 9 V
b) 2.25 V
c) 0.44 V
d) 45 V


                                                16. How much power is dissipated by the resistor shown
                                                to the left?
                                                a) 96 W
                                                b) 12 W
                                                c) 18 W
                                                d) 144 W

17. If a transistor is used as an amplifier in a circuit, the current in the circuit will…
a) Decrease              b) Increase            c) Remain the same d) Become zero

18. Which picture below shows the direction of the electric field near a positive charge?




a)                      b)                      c)                      d)


19. Which diagram below shows the magnetic field between two south poles?


a)                      b)                      c)                      d)



                                                                                                         p. 2
20. The wire shown to the right carries a current that is directed into the page.
What is the direction of the magnetic field near the wire?
a) Up                  b) Down                c) Clockwise            d) Counterclockwise

21. In order to induce an electric current in a nearby wire, a magnetic field must be _______________.
a) Increasing         b) Decreasing            c) Constant          d) Changing

22. Plasmas are gases that have become ionized and contain free _________________.
a) Protons           b) Electrons          c) Neutrons           d) Scions

23. Since a superconductor has no resistance, it won’t generate ______________ when an electric current
travels through it.
a) Heat              b) Current             c) A magnetic field d) An electric field

24. What happens to the amount of current traveling through a circuit when the resistance is increased?
a) The current increases                   b) The current decreases
c) The current remains the same            d) The current no longer flows through the circuit

25. If 3 amps of current travel through the circuit shown to the right, what
is the voltage of the battery?
a) 12 V
b) 24 V
c) 9 V
d) 45 V


26. How much current travels through the 4-ohm resistor in the circuit below?




a) 2.86 A              b) 10 A                c) 4 A                 d) 160 A

27. A 6-Ω motor is connected to a 3-V battery. How much power is dissipated by the motor?
a) 18 W              b) 2 W                c) 0.5 W           d) 1.5 W

28. When placed in a circuit, a transistor can act as an amplifier or a…
a) Superconductor    b) Switch                c) Capacitor            d) Resistor

29. When two negatively-charged objects are placed near each other, the two will ______________.
a) Attract          b) Repel              c) Neither

30. Which diagram best represents the magnetic field around a bar magnet?


a)                     b)                     c)                     d)


                                                                                                      p. 3
31. An electric current travels in a wire to the left. What is the direction of the magnetic field below the
wire?




a) Up                  b) Down                c) Into the page       d) Out of the page

32. Falling water is used to spin a magnet near a coil of wire, inducing a current in the coil as shown in
the diagram below.




Which of the following would decrease the amount of current induced in the wire?
a) Spinning the magnet faster              b) Moving the coil farther from the spinning magnet
c) Using a stronger magnet                 d) Adding more loops of wire to the coil

33. Since plasma has free moving electrons, it is able to conduct _________________.
a) Heat              b) Electricity         c) Energy               d) Magnetic fields

34. To determine the strength of different magnets, a group of students tests how many paperclips they
are able to pick up with each magnet. With the first magnet, one group finds they can pick up 17
paperclips, but a second group is only able to pick up 12 paperclips with the same magnet. Which of the
following would help each group get accurate values in this experiment?
a) Perform multiple trials for each magnet and calculate the average value
b) Perform a single trial using larger paperclips with each magnet
c) Replace the paperclips with steel nails and repeat the experiment
d) Measure the mass of each magnet and use the mass to determine their strength

35. Which tool would not be helpful in verifying Ohm’s Law?
a) Ohmmeter         b) Voltmeter            c) Wattmeter             d) Ammeter

36. Which device is used as an amplifier inside radios, cell phones, and other electronic devices?
a) Capacitor         b) Transistor          c) Superconductor       d) Transducer



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