Question

A wire carrying a current of 3 A is bent in the form of a parabola $y^2=4-x$ as shown in figure, where x and y are in metre.The wire is placed in a uniform magnetic field $\overrightarrow{B}=5\hat{k}$ tesla.The force acting on the wire is

• A. $60\hat{i}N$
• B. $-60\hat{i}N$
• C. $30\hat{i}N$
• D. $-30\hat{i}N$

Answer 1

Answer: (A)

$60\hat{i}N$

At $x=0$
$y=\pm 2m$
$\overrightarrow{F_{MNP}}=\overrightarrow{F_{MP}}=i[\overrightarrow{MP}\times B]$
$=3\left[\right(4\hat{j})\times (5\hat{k}\left)\right]$
$=60\hat{i}$