Two large metal sheets carry surface currents as shown in figure . The current through a strip of width dl is Kdl where K is a constant . Find the magnetic field at the points P,Q and R. `

Explanation

At point P,
Current i=0
So, magneti field B= 0
At point Q,
Applying Ampere's Law
`int B. dl = um_oi`
`rArr B.dl = mu_o kdl`
`rArr B=mu_o^k`
At point R
current I = 0, so, B =0.