Question

Currents of $10 \,A$ and $2 \,A$ are passed through two parallel wires $A$ and $B$ respectively in opposite directions. If the wire is uniformly long and the length of wire $B$ is $2\,m$. The force on conductor $B$ at separation $10 \,cm$ from A will be :

• A. $ 40\times 10^{-7}N $
• B. 8 $ \pi $ $ \times 10^{-7}N $
• C. $ 8\times 10^{-5}N $
• D. $ 4\times 10^{-5}N $

Answer 1

Answer: (C)

Here, $i_{1}=10 \,A, i_{2}=2 \,A$
$ r=10 \,cm =0.1\, m , l=2 \,m$
Using the relation $F=\frac{\mu_{0} i_{1} i_{2} l}{2 \pi R}$
or $F=\frac{4 \pi \times 10^{-7} \times 10 \times 2 \times 2}{2 \pi \times 0.10}$
So, $F=8 \times 10^{-5} N$