Question

A current of $1A$ is flowing along positive $x-axis$ through a straight wire of length $0.5m$ placed in a region of a magnetic field given by $\vec{B}=(2\hat{i}+4\hat{j})T$. The magnitude and the direction of the force experienced by the wire respectively are

• A. $\sqrt{18}N$, along positive z-axis
• B. $\sqrt{20}N$, along positive x-axis
• C. 2N, along positive z-axis
• D. 4N, along positive y-axis

Answer 1

Answer: (C)

The force experienced by the wire placed in magnetic field, $F=Bil$
$=(2\hat{i}+4\hat{j})\left(1\hat{i}\times \frac{1}{2}\right)$
$=\hat{i}\times \hat{i}+4\times \frac{1}{2}(\hat{i}\times \hat{j})=2\hat{k}N$
Direction of this force can be find out by Fleming's left hand rule which is along pasitive z-axis.