Question

Uniform magnetic field B is directed vertically upwards and 3 wires of equal length L, carrying equal current l are lying in a horizontal plane such that the first one is along the north, the second one along north-east and the third one at ${60}^0$ north of east. Force exerted by magnetic field B on them is

• A. zero on the first
• B. $\frac{BlL}{\sqrt{2}}$ on the second
• C. $\sqrt{3}\frac{BlL}{\sqrt{2}}$ on the third
• D. BlL on all of them

Answer 1

The correct option is D BlL on all of them

If magnetic field is vertical each wire make angle ${90}^{\circ }$ with vertical.

So each wire experience force

$f=iL\times B=iLB\sin {90}^{\circ }=BIL$