A flat coil of wire, having 5 turns, has an inductance L. The inductance of a similar coil having 20 turns is:
A) 4L
B) L/4
C) 16L
D) L/16
E) L

Question

Quizplus · Accepted Answer

The inductance of a coil is directly proportional to the square of the number of turns (N^2). Therefore, if the number of turns increases from 5 to 20 (which is a factor of 4), the inductance increases by a factor of 4^2 = 16. Hence, the inductance of the coil with 20 turns is 16L.

A Flat Coil of Wire, Having 5 Turns, Has an Inductance