$A$ uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure. In the field,an electron and a proton move as shown. The electron and the proton experience:

What is the nature of the magnetic field produced by a current-carrying circular coil? Explain with the help of an experiment.

$A$ current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and a point directly above it?

Who first observed the magnetic effect of an electric current?

$A$ square coil moves in a plane with uniform velocity $v$ parallel to its sides. $A$ magnetic field $B$ points perpendicular and into the loop. What is the induced current in the coil?

$(a)$ Define electromagnetic induction.
$(b)$ Two coils $P$ and $S$ are wound over the same iron core. Coil $P$ is connected to a battery and a key,and coil $S$ is connected to a galvanometer. Draw a suitable diagram of this arrangement and write your observations when:
$(i)$ current in the coil $P$ is started by closing the key.
$(ii)$ current continues to flow in coil $P$.
$(iii)$ current in coil $P$ is stopped by removing the key.
Explain the reason for such observations.