Question

Draw a diagram representing the magnetic field inside and outside a solenoid through which a current is flowing and mark with arrows, the direction of current in the solenoid and the direction of magnetic field lines. Also mark the polarity at the faces of solenoid. A bar of soft-iron is then placed parallel to its length inside the solenoid. Describe what happens.

Answer 1

Fig. shows the magnetic field lines due to a current carrying solenoid. The direction in the solenoid at the face A is clockwise, so it will have the south ( *) polarity and the face B of solenoid will have the north (N) polarity.

If a bar of soft iron is placed parallel to its length inside the solenoid, the magnetic field inside the solenoid becomes closer i.e. the magnetic field inside the solenoid is increased.