Question

A wire ABCDEF is bent in the form as shown in figure. The wire carries a current I and is placed into a uniform magnetic field of induction B parallel to positive Y-axis. If each side is of length L, the force experienced by the wire will be :

• A. IBL along the positive Z-direction
• B. IBL along the negative Z-direction
• C. 2IBL along the positive Z-direction
• D. 2IBL along the negative Z-direction

Answer 1

The correct option is A IBL along the positive Z-direction

Here we need to apply the Fleming's left hand rule to find force on a current carrying conductor in magnetic field.

Here we will consider each line segments separately.

For the segment

1. FE

$F=iL\times B=0$

because here current is parallel to the magnetic field.

2. ED

$F=-iLB\hat{i}$

Force will be along negative x-axis

3. DC

$F=iLB\hat{k}$

Force will be along positive z-axis

4. CB

$F=iLB\hat{i}$

Force will be along positive x-axis

5. BA

$F=iL\times B=0$

Force will be zero because the current is parallel to the magnetic field.

From above we can see that 2 and 4 will cancel out each other.

So net force will be along positive z-axis.

Hence, option 'A' is correct.