Question: Q. 2. Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current.
R [O.D. I, II, III 2014]
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Solution:
Ans. Definition : One ampere is the value of steady current which when maintained in each of the two very long, straight, parallel conductors of negligible cross-section and placed one metre apart in vacuum, would produce on each of these conductors a force equal to $2 \times 10^{-7} \mathrm{~N} / \mathrm{m}$ of its length.
Alternatively :
$$ F=\frac{\mu_{0}}{2 \pi} \frac{I_{1} I_{2}}{r} L $$
and says that when
$I_{1}=I_{2}=1$ ampere
$r=1$ metre and $L=1$ metre, then
$F=2 \times 10^{-7} \mathrm{~N}$
Alternatively,
[CBSE Marking Scheme, 2014]
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