Electricity Test paper 10
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June 27, 2015 |
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1. Name two safety measures commonly used in electric circuits and appliances. (1marks)
2. State advantages of the third wire of earth connection in domestic electric appliances? (1mark)
3. How can it be shown that a magnetic field exists around a wire through which a direct electric current is passing? (1 mark)
4. Where is the magnetic field due to current through a circular loop is uniform? (1 mark)
5. Why does a compass needle get deflected when brought near a bar magnet? (2 marks)
6. Why don’t two magnetic lines of force intersect each other? (2 marks)
7. Explain different ways to induce current in a coil. (2 marks)
8. The essential difference between an AC generator and a DC generator is that (2 marks)
(i) AC generator has an electromagnet while a DC generator has permanent magnet
(ii) DC generator will generate a higher voltage.
(iii) AC generator will generate a higher voltage.
(iv) AC generator has slip rings while the DC generator has a commutator.
9. Write function of an earth wire? Why is it necessary to earth metallic appliances? (2 marks)
10. List the properties of magnetic lines of force. (3 marks)
11. Write precautions to be taken to avoid the overloading of domestic electric circuits? (3)
12. Explain the principle, construction and working of an AC generator, showing the output.
What is the function of brushes? (5 marks)
13. What is the effect of placing an iron core in a solenoid? (1mark)
14. How much force is exerted by a magnetic field on a stationary charge? (1mark)
15. What is the effect of increasing the number of turns on the magnetic field produced due
to a circular coil? (1mark)
16. Name the device which converts mechanical energy into electrical energy. (1mark)
17. Explain why the direction of induced current in the coil of an AC generator changes after
energy half revolution of the coil. (2 marks)
18. Why does a current – carrying conductor experience a force in a magnetic field? (2marks)
19. Why do we use power supply of two different current ratings at our homes? (2 marks)
20. What is an electric fuse? What material is selected for fuse wire? (2marks)
21. Explain the use of an electric fuse. (2 marks)
22. What is the difference between direct current and alternating current? (2 marks)
23. Draw the pattern of field lines due to a bar magnet. Mention any two properties of the
magnetic field lines. (3 marks)
24. Give three advantages of electromagnet over a permanent magnet? (3marks)
25. Give three points of differences between an electromagnet and a permanent magnet. (3
marks)
26. Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor? (5 marks)
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