Question

Currents of a $10$ ampere and $2$ ampere are passed through two parallel thin wires $A$ and $B$ respectively in opposite directions. Wire $A$ is infinitely long and the length of the wire $B$ is $2\, m$. The force acting on the conductor $B$, which is situated at $10\, cm$ distance from $A$ will be

• A. $8 \times 10^{-5}\,N$
• B. $5 \times 10^{-5}\,N$
• C. $8 \pi\times 10^{-7}\,N$
• D. $4 \pi\times 10^{-7}\,N$

Answer 1

Answer: (A)

$8 \times 10^{-5}\,N$

Answer 2

Force acting on conductor B due to conductor A is given by relation $F = \frac{\mu_{0}I_{1}I_{2}l}{2\pi r}$ $l$-length of conductor B $r$-distance between two conductors $\therefore F = \frac{4\pi \times 10^{-7}\times 10\times 2\times 2}{2\times \pi\times 0.1} = 8\times 10^{-5}\,N$