$(a)$ What is electromagnetic induction?
$(b)$ In what way can the magnitude of the induced current be increased?

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

Which instrument works on the principle of 'Electromagnetic induction'?

In our daily life,we use two types of electric current whose current-time graphs are given below:
$(i)$ Name the type of current in two cases.
$(ii)$ Identify any one source for each type of current.
$(iii)$ What is the frequency of current in case $(b)$ in our country?
$(iv)$ On the basis of these graphs,list two differences between the two currents.
$(v)$ Out of the two,which one is used in transmitting electric power over long distances and why?

$(a)$ Describe an activity to show the pattern of magnetic field lines of a bar magnet,with the help of a cardboard piece and iron filings.
$(b)$ Compare the magnetic field of a bar magnet with that of a current-carrying solenoid with the help of a figure.

$(a)$ 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.