Question

Constant current is sent through a helical coil. The coil :
A) tends to get shorter
B) tends to get longer
C) tends to rotate about its axis
D) Produces zero magnetic field at its center

Answer 1

A)
It will tend to shorten ,just use the direction of current to find the direction of magnetic field on the wires near and opposite to it.
Then since you have the direction of the current in those wires find the direction of force on them .
You'll find that the force is radially inward (almost).