Moving Charges and Magnetism - Result Question 71
72. Two long parallel wires are at a distance of 1 metre. Both of them carry one ampere of current. The force of attraction per unit length between the two wires is
(a) $2 \times 10^{-7} N / m$
(b) $2 \times 10^{-8} N / m$
(c) $5 \times 10^{-8} N / m$
(d) $10^{-7} N / m$
[1998]
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Answer:
Correct Answer: 72. (a)
Solution:
- (a) $F=\frac{\mu_0}{4 \pi} \times \frac{2 i_1 i_2 l}{r}=10^{-7} \times \frac{2 \times 1 \times 1 \times 1}{1}$
$=2 \times 10^{-7} N / m$.
[This relates to the definition of ampere]
