Question

A coil having 12 turns is connected to a battery as shown. The magnetic field at the axis of the helix will be ___ the magnetic field at the center of a similar circular loop but with a single turn.

• A. greater than
• B. equal to
• C. lesser than
• D. opposite in direction to

Answer 1

The correct option is C lesser than

The magnetic field at the centre of a loop is a straight line due to the sum of components of magnetic fields at the centre due to different parts of the loop.

When we take a coil having 12 turns, the magnetic field at the axis is the sum of magnetic fields from each loop of the coil. Hence, it is 12 times the magnetic field due to a single loop, since the radii are the same.