The branch of science that covers the comprehensive study of electricity and magnetism is known as $.........$.

State the direction of the magnetic field in the following case:

When is the force experienced by a current-carrying conductor placed in a magnetic field the largest?

By which instrument can the presence of a magnetic field be determined?

How can we find the direction of the magnetic field due to a straight current-carrying conductor?

$(a)$ $A$ coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is:
$(i)$ pushed into the coil with its north pole entering first?
$(ii)$ withdrawn from inside the coil?
$(iii)$ held stationary inside the coil?
$(b)$ Name the above phenomenon and mention the name of the scientist who discovered it. State the law that relates the direction of current in the coil with the direction of motion of the magnet.