A small iron bar is kept near the north pole of a bar magnet. How does the iron bar acquire magnetism? Draw a diagram to show the polarity on the iron bar. What will happen if the magnet is removed?

Explain the method of plotting magnetic field lines by using a small compass needle.

Look at the figure and answer the following questions:

(i) The end P becomes:

1. south pole
2. north pole
3. cannot say
4. none of the above

(ii) The end Q becomes:

1. south pole
2. north pole
3. cannot say
4. none of the above

(iii) The given bar shows magnetic properties only when …………… through the solenoid and it loses the magnetic properties as soon as the ……………

1. current is switched off, current is switched on
2. current is switched on, current is switched off
3. current is switched on, current is switched on
4. both (a) and (b)

The magnetic field of an electromagnet can be increased by …………… in the solenoid and by ……………through the solenoid.

1. increasing the number of turns, decreasing the current.
2. decreasing the number of turns, increasing the current.
3. decreasing the number of turns, decreasing the current.
4. increasing the number of turns, increasing the current.