Electromagnetic Induction Practice Test 1

1.

A circular loop of radius 0.10 m is placed in a uniform magnetic field of 0.5 T. The field is perpendicular to the plane of the loop. If the field is reduced to zero in 0.2 s, what is the magnitude of the average induced emf?

a) 0.039 V b) 0.079 V c) 0.16 V d) 0.25 V

2.

Which of the following best describes Lenz's law?

a) The induced emf always opposes the change in magnetic flux b) The induced emf is always positive c) The induced emf is proportional to the area d) The induced emf is independent of time

3.

A straight conductor of length 0.5 m moves at 3 m/s perpendicular to a 0.2 T magnetic field. What is the induced emf across its ends?

a) 0.03 V b) 0.10 V c) 0.15 V d) 0.30 V

4.

Which of the following best describes the unit of inductance?

a) Tesla b) Henry c) Weber d) Farad

5.

Which of the following best describes the direction of the induced current in a loop when the magnetic flux through the loop increases into the page?

a) Clockwise b) Counterclockwise c) Upward d) Downward

6.

A coil of 200 turns and area 0.01 m² is placed in a uniform magnetic field of 0.2 T. The field is reduced to zero in 0.1 s. What is the average induced emf?

a) 0.2 V b) 0.4 V c) 0.8 V d) 1.2 V

7.

Which of the following best describes the time constant in an RL circuit?

a) L/R b) R/L c) RC d) 1/RC

8.

Which of the following best describes the induced emf in a coil when the magnetic flux is constant?

a) Maximum b) Zero c) Depends on the area d) Depends on the number of turns

9.

A 0.2 m long rod moves at 5 m/s perpendicular to a 0.3 T magnetic field. What is the induced emf across its ends?

a) 0.03 V b) 0.15 V c) 0.30 V d) 0.60 V

10.

A coil is connected to a sensitive galvanometer. When a bar magnet is quickly inserted into the coil, the galvanometer needle deflects to the right. What happens if the magnet is withdrawn quickly instead?

a) The needle deflects to the right again b) The needle deflects to the left c) The needle does not move d) The needle vibrates rapidly

11.

A bar magnet is pushed into a coil (north pole first). What is the direction of the induced current (viewed from the magnet side)?

a) Clockwise b) Counterclockwise c) Upward d) Downward

12.

A coil of 50 turns and area 0.02 m² is placed in a uniform magnetic field of 0.3 T. The field is reduced to zero in 0.5 s. What is the average induced emf?

a) 0.6 V b) 0.3 V c) 0.12 V d) 0.09 V

13.

A straight conductor of length 0.4 m moves at 2 m/s perpendicular to a 0.25 T magnetic field. What is the induced emf across its ends?

a) 0.10 V b) 0.15 V c) 0.20 V d) 0.25 V

14.

A coil of 100 turns is placed in a magnetic field. The flux through the coil changes by 0.05 Wb in 0.1 s. What is the average induced emf?

a) 25 V b) 50 V c) 100 V d) 500 V

15.

A 0.3 m metal rod moves to the right at 4 m/s on conducting rails in a magnetic field of 0.2 T directed into the page. What is the emf across the rod?

a) 0.06 V b) 0.12 V c) 0.18 V d) 0.24 V

16.

Which of the following best explains why a transformer only works with AC and not DC?

a) AC produces a changing magnetic flux b) DC produces a stronger field c) AC is safer d) DC reverses direction

17.

A rectangular loop is pulled at constant speed from a region with magnetic field into a region with no field. What happens to the induced current as the loop leaves the field?

a) It increases b) It decreases to zero c) It reverses direction d) It remains constant

18.

A coil of 20 turns and area 0.01 m² is perpendicular to a 0.4 T magnetic field. If the field drops to zero in 0.2 s, what is the average induced emf?

a) 0.04 V b) 0.08 V c) 0.16 V d) 0.40 V

19.

Suppose you double the speed at which a magnet is pushed into a coil. What happens to the peak induced emf?

a) It doubles b) It halves c) It stays the same d) It becomes zero

20.

A 0.5 m rod moves at 6 m/s perpendicular to a 0.1 T magnetic field. What is the emf across its ends?

a) 0.03 V b) 0.15 V c) 0.30 V d) 0.60 V

21.

Which of the following would increase the energy stored in an inductor?

a) Increasing the current b) Decreasing the inductance c) Decreasing the current d) Decreasing the number of turns

22.

A transformer has 200 turns on the primary and 1000 turns on the secondary. If the input voltage is 120 V, what is the output voltage (ideal transformer)?

a) 24 V b) 60 V c) 600 V d) 1200 V

23.

Which of the following best describes the effect of increasing the resistance in the secondary coil of a transformer?

a) Increases the current b) Decreases the current c) No effect d) Increases the voltage

24.

A coil of 10 turns and area 0.05 m² is perpendicular to a 0.2 T magnetic field. If the field drops to zero in 0.1 s, what is the average induced emf?

a) 0.05 V b) 0.10 V c) 0.20 V d) 0.40 V

25.

Suppose a coil is connected to a sensitive ammeter. A magnet is dropped through the coil. What does the ammeter show?

a) A steady current in one direction b) A current that reverses direction c) No current d) A current only as the magnet enters

26.

Which of the following best describes the effect of increasing the resistance in an RL circuit on the maximum current?

a) Increases the maximum current b) Decreases the maximum current c) No effect d) Reverses the current direction

27.

A 0.2 m rod moves at 3 m/s perpendicular to a 0.4 T magnetic field. What is the emf across its ends?

a) 0.12 V b) 0.24 V c) 0.36 V d) 0.60 V

28.

A student graphs the current in an RL circuit as a function of time after the switch is closed. What does the graph look like?

a) Linear increase b) Exponential increase c) Exponential decrease d) Constant

29.

Which of the following best describes the effect of increasing the area of the secondary coil in a transformer?

a) Increases the output voltage b) Decreases the output voltage c) No effect d) Reverses the current direction

30.

A coil of 25 turns and area 0.04 m² is perpendicular to a 0.5 T magnetic field. If the field drops to zero in 0.2 s, what is the average induced emf?

a) 0.10 V b) 0.20 V c) 0.25 V d) 0.50 V

Electromagnetic Induction Practice Test 1

30 Challenging Questions – AP Physics C Level