Question

What is the expression for the force experienced by two parallel current carrying conductors of unequal length?

(a) F=\(\frac {\mu_o}{4\pi } \times \frac {2I_1 I_2}{r}\) × l

(b) F=\(\frac {\mu_o}{4\pi } \times \frac {I_1 I_2}{r}\) × l

(c) F=\(\frac {\mu_o}{4\pi } \times \frac {\frac {2I_1 I_2}{r}}{l}\)

(d) F=\(\frac {\mu_o}{4\pi } \times \frac {2I_1 I_2}{4r}\) × l

The question was posed to me during an online interview.

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

Answer 1

The correct choice is (a) F=\(\frac {\mu_o}{4\pi } \times \frac {2I_1 I_2}{r}\) × l

The best I can explain: If two linear current carrying conductors of unequal length are held parallel to each other, then the force on a long conductor is due to magnetic field interaction due to currents of short conductor and long conductor. The force on long conductor is force to that on the short conductor given by:

F=\(\frac {\mu_o}{4\pi } \times \frac {2I_1 I_2}{r}\) × l