In which case is there an induced electromotive force?

An electromagnet operating on direct current is held inside a second coil of wire.

An electromagnet operating on alternating current is held inside a second coil of wire.

A permanent bar magnet is held inside a coil of wire.

Field lines from earth's magnetic field cross the area of a coil of wire.

Question

In which case is there an induced electromotive force?
    
   An electromagnet operating on direct current is held inside a second coil of wire.

       An electromagnet operating on alternating current is held inside a second coil of wire.

       A permanent bar magnet is held inside a coil of wire.

       Field lines from earth's magnetic field cross the area of a coil of wire.

izzyrawrz · Answer

@cookiimonster27

jtvatsim · Answer

Electromotive force is generated whenever there is a [change] in magnetic flux. Does this help you rule out any of the answer choices?

izzyrawrz · Answer

No...I am really bad at physics, please help.

anonymous · Answer

EMF proportional to change of magnetic flux per time through a loop, so rule out A, C, D.

izzyrawrz · Answer

Thanks :)

anonymous · Answer

You're welcome