CUET Preparation Today
A square loop is placed near a long straight current carrying wire as shown in figure. If the loop is moved away from the wire.
|
Induced current in loop will be anti-clockwise Wire will exert net attractive force on the loop Wire will exert net repulsive force on the loop No current is induced in the loop |
Wire will exert net attractive force on the loop |
The correct answer is Option (2) → Wire will exert net attractive force on the loop Magnetic field at distance $r$ from the long straight wire: $B=\frac{\mu_0 i}{2\pi r}$. As the loop is moved away, $B$ through the loop decreases. By Lenz's law the induced current produces a field to oppose this decrease, hence induced current is clockwise (viewed from front) so as to produce $B$ into the page. Left (near) side current is upward (parallel to wire current) → attraction. Right (far) side current is downward (antiparallel) → repulsion, but weaker because $B$ is smaller there. Net force on the loop is attractive. |
