### NEET Solved Paper 2018 Question 26

##### Question: A metallic rod of mass per unit length $ 0.5kgm^{1} $ is lying horizontally on a smooth inclined plane which makes an angle of $ 30{}^\circ $ with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is [NEET - 2018]

#### Options:

A) $ 14\text{.76 A} $

B) $ 5\text{.98 A} $

C) $ 7\text{.14 A} $

D) $ 11\text{.32 A} $

## Show Answer

#### Answer:

Correct Answer: D

#### Solution:

For equilibrium,

$ \text{mg sin30}{}^\circ \text{=I}l\text{B cos 30}{}^\circ $

$ \text{I=}\frac{mg}{lB}\tan 30{}^\circ $ $ =\frac{0.5\times 9.8}{0.25\times \sqrt{3}}=11.32A $