Question

Two large metal sheets carry 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.

Answer 1

At point P,
Current, i = 0
∴ Magnetic field B = 0
At point Q,
Applying Ampere's law, we get
$$\begin{gathered} \int \mathrm{B}.dl={\mu }_{0}i \\ \Rightarrow \mathrm{B}.dl={\mu }_{0}kdl \\ \Rightarrow \mathrm{B}={\mu }_{0}k \end{gathered}$$
At point R,
Current, i = 0
∴ B = 0