Question

Name the device used to magnetise a piece of magnetic material. Draw a labelled diagram to show the arrangement used for the magnetisation of a cylinder made of soft iron.

Assertion (A) : The deflection of a compass needle placed near a current carrying wire decreases when the magnitude of an electric current in the wire is increased. Reason (R) : Strength of the magnetic field at a point due to a current carrying conductor increases on increasing the current in the conductor.

Draw a diagram to show the pattern of magnetic field lines on a horizontal sheet of paper due to a straight conductor passing through its centre and carrying current vertically upwards. Mark on it (i) the direction of current in the conductor and (ii) the corresponding magnetic field lines. State right hand thumb rule and check whether the directions marked by you are in accordance with this rule or not.

Ravi performed an experiment in his school laboratory to study the magnetic effect of electric current. He passed electric current through a straight copper conductor placed near a magnetic compass. He observed that the compass needle deflected when current flowed through the conductor. When the direction of current was reversed, the direction of deflection of the compass needle also reversed. Later, Ravi used a solenoid connected to a battery and placed a soft iron core inside it. He observed that the solenoid behaved like a bar magnet when current flowed through it and lost its magnetism when the current was switched off.