Question

Pick out the expression for force per unit length between two parallel carrying conductors if the current passing through both of them are the same?

(a) \(\frac {\mu_o 2I^2}{4πb}\)

(b) \(\frac {\mu_o 2I^3}{4πb}\)

(c) \(\frac {\mu_o I^2}{4πb}\)

(d) \(\frac {\mu_o 4I^2}{4πb}\)

I had been asked this question during a job interview.

This interesting question is from Ampere and Forces between Two Parallel Currents topic in portion Moving Charges and Magnetism of Physics – Class 12

Answer 1

The correct option is (b) \(\frac {\mu_o 2I^3}{4πb}\)

Explanation: The expression for force between 2 parallel current carrying conductors is given by:

f=\(\frac {\mu_o}{4\pi } \big [ \frac {I_1 I_2}{b} \big ] \)

In this case, the current passing through both of them are the same, i.e. I1=I2

Therefore, the force per unit length is given as:

f=\(\frac {\mu_o}{4\pi } \big [ \frac {I^2}{b} \big ] \)