Which of the following statements is not true ?

1. The strength of magnetic field due to a bar magnet can be changed.
2. A solenoid behaves like a bar magnet i.e. it attracts iron filings.
3. The magnetic field increases if a soft iron core is placed along the axis of solenoid.
4. The magnetic field lines inside the solenoid are nearly straight and parallel to the axis of solenoid.

Which of the following statements is not true for an electromagnet ?

1. It is made of soft iron.
2. Its magnetic field strength can be changed.
3. The polarity of an electromagnet cannot be changed.
4. It can easily be demagnetised.

On reversing the direction of current in a wire, the magnetic field produced by it:

1. gets reversed in direction
2. increases in strength
3. decreases in strength
4. remains unchanged in strength and direction.

A strong permanent magnet is made of :

1. soft iron
2. steel
3. nickel
4. copper