Question

The electromagnet in which of the following diagrams will generate a magnetic field that periodically reverses its orientation?


W.
X.

Y.
Z.
A.
W
B.
Y
C.
X
D.
Z

Answer 1

I can't see the diagrams you mean — could you upload the image or describe each diagram (what each coil is connected to: battery, AC source, generator, commutator, etc.)?

General rule you can use to pick the correct diagram:
- The magnetic field of an electromagnet reverses whenever the direction of the current in the coil reverses.
- That happens periodically if the coil is fed from an alternating-current source (AC symbol ~) or any circuit that causes the coil current to reverse periodically.
- A simple DC battery produces a steady (non-reversing) magnetic polarity.
- Devices like an AC generator or a coil connected through slip rings to an AC source will produce a periodically reversing field. A plain DC battery with no reversing switch/commutator will not.

If you send the diagrams or describe what each coil is connected to, I’ll pick the correct letter and explain why.