Question

One ampere is the current which when flowing through each of two parallel wires spaced one meter apart in vacuum and of infinite length will give rise to a force between then equal to

• A. $1$ N/m
• B. $1\times {10}^{-2}$N/m
• C. $2\times {10}^{-7}$N/m
• D. $4\pi \times {10}^{-7}$N/m

Answer 1

Answer: (C)

$2\times {10}^{-7}$N/m

Force per unit length on two parallel current carrying conductor is given by

$\frac{F}{l}={10}^{-7}\times 2\frac{i_1{i}_2}{a}$

$\Rightarrow \frac{F}{l}={10}^{-7}\times 2\frac{1\times 1}{1}$

$=2\times {10}^{-7}N/m$