In the figure given below, current is passed in a downward direction through a cardboard. The magnetic field lines would be :

1. straight lines
2. concentric circles
3. elliptical lines
4. squares

According to the right hand thumb rule, the thumb points in the direction of …………… and fingers encircle the wire in direction of ……………

1. magnetic field lines, current
2. electric field lines, current
3. current, magnetic field lines
4. none of the above

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.