Question

A copper rod of length L and mass m is sliding down a smooth inclined plane of inclination $\theta$ with a constant
speed v. A current I is flowing in perpendicular to the plane of diagram inwards. A vertically upward magnetic
field $\overrightarrow{B}$ exist in this region.The magnitude of the required magnetic field $\overrightarrow{B}$ is

• A. $\frac{mg}{IL}sin\theta$
• B. $\frac{mg}{IL}sin\theta$
• C. $\frac{mg}{IL}tan\theta$
• D. $\frac{mg}{ILsin\theta }$

Answer 1

The correct option is C

$\frac{mg}{IL}tan\theta$

BIL $cos\theta =mgsin\theta$ or $B=\frac{mg}{IL}\frac{sin\theta }{cos\theta }=\frac{mg}{IL}tan\theta$