#### Term 2 Magnetism and Electromagnetism Three Marks Questions

9th Standard

Reg.No. :
•
•
•
•
•
•

Science

Time : 00:45:00 Hrs
Total Marks : 30
10 x 3 = 30
1. State an important advantage of ac over dc.

2. A portable radio has a built in transformer so that if can work from the mains instead of batteries. Is this a step up or step down transformer?

3. Two coils A and B of insulated wire are kept close to each other. Coil A is connected to a galvanometer. While coil B is connected to a battery through a key. What would happen if
(i) a current is passed through coil B by plugging the key?
(ii) the current is stopped by removing the plug from the key?

4. State Faraday’s laws of electromagnetic induction.

6. Give some uses of electromagnets

7. A conductor of length 50 cm carrying a current of 5 A is placed perpendicular to a magnetic field of induction 2×10-3 T. Find the force on the conductor.

8. A current carrying conductor of certain length, kept perpendicular to the magnetic field experiences a force F. What will be the force if the current is increased four times, length is halved and magnetic field is tripled?

9. The primary coil of a transformer has 800 turns and the secondary coil has 8 turns. It is connected to a 220 V ac supply. What will be the output voltage?

10. A transformer is designed to give a supply of 8 V to ring a house bell from 240 V ac mains. The primary coil has 4800 turns. How many turns will be in the secondary coil.