Question

TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false.
11) A changing magnetic field can produce an electric current.
12) An emf is induced in a wire by moving the wire near a magnet.
13) A constant magnetic field can be used to produce an electric current.
14) An electric generator is a device that converts electrical energy into mechanical energy.

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
15) Faraday's law of induction states that the emf induced in a loop of wire is proportional to A) the magnetic flux density times the loop's area.
B) the magnetic flux.
C) current divided by time.
D) the time variation of the magnetic flux.
16) An electric generator transforms.
A) direct current into alternating current.
B) mechanical energy into electrical energy.
C) electrical energy into mechanical energy.
D) alternating current into direct current.
E) chemical energy into electrical energy.
17) A transformer is a device that
A) operates only on AC.
B) increases the power level of a circuit.
C) operates only on DC.
D) operates on either DC or AC.
18) In a transformer, the power input
A) can be either larger or smaller than the power output.
B) is larger than the power output.
C) is equal to the power output.
D) is smaller than the power output.

TRUE/FALSE.
19) An ac signal of a certain frequency is applied to a capacitor. The current leads the voltage by 90°.
20) The capacitive reactance increases with the capacitance

Answer 1

11)

T

[the reason is the change in magnetic field produces a change in magnetic flux which produces an emf creates a current]

12)

T

[moving near a magnet changes the magnetic lines linked with the wire so flux is changed]

13)

F

14)

F

[ converts mechanical to electrical energy]

15)

Answer is

D) the time variation of the magnetic flux

[this is because change in flux cretes an emf]

16)

Answer is

B) mechanical energy into electrical energy.

[A loop rotating mechanically creates an electrical energy]

17)

Answer is

B) increases the power level of a circuit.

18)

A) can be either larger or smaller than the power output.

19)

T

[ in inductance the current lags over voltage where as in capacitor the current leads the voltage]

20)

F

[ the capacitive reactance is 1/(omega*C) so it decreases with capacitance]