43. NCERT Exemplar VII

1. A magnetic compass needle is placed in the plane of paper near point A as shown in figure. In which plane should a straight current carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

 

 

The current carrying conductor is placed in the plane of the paperperpendicular to the paper itself. This is because the axis of the compass is horizontalvertical and the field due to the conductor is also horizontalalso vertical. The deflection is minimunmaximum when the conductor passes through A in a plane perpendicularparallel to the plane of paper. This is because the field is maximum in the perpendicular to the papermaximum in the plane of the paper.

 

2. Under what conditions permanent electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.

 

Conditions in which a permanent electromagnet is obtained if a current carrying solenoid is used are:

 

i. The magnitude of direct current through the solenoid should be .lowlarge

 

ii. The number of turns in the solenoid should be lowlarge and loosely packedclosely packed, so that a strong uniform magnetic field inside it is produced.

 

iii. The rod kept inside is made of a magnetic materialnon magnetic material.