# NCERT Exemplar Class 10 Science Chapter-13Magnetic Effects of Electric Current

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## NCERT Exemplar Class 10 Science Chapter-13Magnetic Effects of Electric Current

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?

Answer. In the given situation, a straight current-carrying conductor should be placed in the plane of paper. The held produced by it is perpendicular to the plane of paper and parallel to the vertical axis of compass needle. As a result there will be no change in the deflection of compass needle.
The deflection is maximum when the straight current carrying conductor through the point A is perpendicular to the plane of paper so that field due to it is parallel to the plane of 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.
(i) The magnitude of direct current through the solenoid should be large.
(ii)The number of turns in the solenoid should be large and closely packed, so that a strong uniform magnetic field inside it is produced.
(iii) The rod kept inside is made of a magnetic material such as steel.

3.AB is a current carrying conductor in the plane of the paper as shown in figure. What are the directions of magnetic fields produced by it at points P and Q? Given r1 > r2, where will the strength of the magnetic field be larger?

Answer. Apply right hand thumb rule, the direction of magnetic field produced by a current carrying conductor at Point P – into the plane of paper
Point Q – out of the plane of paper.
As magnetic field is inversely proportional to distance, the field at Q will be larger than the field at P ( r1 > r2).

4.It is established that an electric current through a metallic conductor produces a magnetic field around it. Is there a similar magnetic field produced around a thin beam of moving (i) alpha particles, (ii) neutrons? Justify your answer.
(i) Yes, similar magnetic field is produced around a thin beam of moving a-particle. a-particle being positively charged constitutes a current in the direction of beam motion.
(ii) No, neutron being electrically neutral, does not constitute a current.

5.Name four appliances wherein an electric motor, a rotating device that converts electrical energy to mechanical energy, is used as an important component. In what respect motors are different from generators?
Answer.The four appliances wherein electric motor, a rotating device that converts electrical energy into mechanical energy is used are electric fan, water pump, grinder and washing machine.
Difference between electric motor and generator:

 Electric Motor Electric Generator (a) It converts electrical energy into mechanical energy. (a) It converts mechanical energy into electrical energy. (b) It works on the principle of magnetic effect of electric (b) It works on the phenomenon of electromagnetic induction.

6.What is the role of the two conducting stationary brushes in a simple electric motor?
Answer.The two stationary conducting brushes make the contact in between the two halves of the split rings and the source battery. Current in the coil enters from the source battery through one conducting brush and flows back to the battery through another brush.