MCQ
In given figure, $X$ and $Y$ are two long straight parallel conductors each carrying a current of $2\,\, A.$ The force on each conductor is $F$ newtons. When the current in each is changed to $1\, A $ and reversed in direction, the force on each is now
  • $F/4$ and unchanged in direction
  • B
    $F/2$ and reversed in direction
  • C
    $F/2$ and unchanged in direction
  • D
    $F/4$ and reversed in direction

Answer

Correct option: A.
$F/4$ and unchanged in direction
a
$F=\frac{\mu_{0}}{4 \pi} \frac{2 I_{1} I_{2}}{d}$

$F=\frac{\mu_{0}}{4 \pi} \frac{2 \times 2 \times 2}{d} \times l$

$F^{\prime}=\frac{\mu_{0}}{4 \pi} \frac{2 \times 1 \times 1}{d} \times l=\frac{F}{4}$

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