Which of the following factors could you change in a system and not change its induced emf?

The options attached to the question above are listed below:
A. Magnetic field.
B. Type of wire.
C. Velocity of the wire.
D. Length of the wire in the field.

ANSWER
The correct option is B.
The factors that determine the induced current in a system are: the number of wires in the coil, the strength of the magnetic field and speed of armature rotation [speed of cutting]. Generally, the induced electromotive force across a conductor is equal to the rate at which magnetic flux is cut by the conductor. The type of wire used does not affect the induced EMF.

The density would be 1.622