Two parallel beams of electrons moving in the same direction produce a mutual force:

Choose the correct statement.

Two parallel beams of protons and electrons,carrying equal currents,are fixed at a separation $d$. The protons and electrons move in opposite directions. $P$ is a point on a line joining the beams,at a distance $x$ from the proton beam. The magnetic field at $P$ is $B$. If $B$ is plotted against $x$,which of the following best represents the resulting curve?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$(A)$ Permeability of free space	$(I) \ [M L^2 T^{-2}]$
$(B)$ Magnetic field	$(II) \ [M T^{-2} A^{-1}]$
$(C)$ Magnetic moment	$(III) \ [M L T^{-2} A^{-2}]$
$(D)$ Torsional constant	$(IV) \ [L^2 A]$

Choose the correct answer from the options given below:

The adjoining figure shows a very long semi-cylindrical conducting shell of radius $R$ carrying a current $i$. An infinitely long straight current-carrying conductor is lying along the axis of the semi-cylinder. If the current flowing through the straight wire is $i_0$,then the force per unit length on the conducting wire is

Which of the following statements is correct?