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Flux change

Flux change. The coil is moving towards the north pole of the magnet. The flux linkage of the coil is increasing. EM Induction. Class example. S. . . S. . Right hand rule. Class example. Class example. I. Alternator. I. X. Note that there is no power supply!. View form X.

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Flux change

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  1. Flux change The coil is moving towards the north pole of the magnet.

  2. The flux linkage of the coil is increasing.

  3. EM Induction

  4. Class example S   S 

  5. Right hand rule

  6. Class example

  7. Class example I

  8. Alternator I X Note that there is no power supply!

  9. View form X

  10. Class example

  11. Dynamo I - +

  12. Induction cooker

  13. a.c. power supply

  14. Y-gain = 50 mV cm-1 Time base = 50 ms cm-1

  15. Transformer I Power station Step-up transformer Step-down transformer V Consumer P = power input from power station V = voltage after stepping up I = current flowing through the cable

  16. We have the followings: • P is fixed • As V is large, I becomes small • Heat loss in the cable = 2  power loss in the cable becomes smaller

  17. Class example(P.241#7) • Total resistance of cable • = 0.165  10  2 • = 3.3  (b) Voltage drop along the line = I R = 400  3.3 = 1320 V

  18. (c) Power input to the line = V I = 132000  400 = 52800000 W = 52.8 MW

  19. (d) Power lost in the line = I2 R = 4002 3.3 = 528000W = 0.528 MW

  20. (e) The ‘lost’ energy is changed into internal energy in the cable and then changed into heat energy in the environment.

  21. (f) The primary coil should have larger number of turns. The number of turns in primary coil is 550 times of that of the secondary coil.

  22. (g) By P = V I 1440000 = 240 IS IS = 600 A (h) The machines and electrical appliances used in factories and homes are not .

  23. (h) The machines and electrical appliances used in factories and homes are not designed to be operated at such a high voltage and hence it is very dangerous.

  24. 92CEII#35 Which of the following can increase the efficiency of a transformer?  (1) Increasing the number of turns of the secondary coil.  (2) Using a laminated iron core.  (3) Using thicker copper wires to make the coils .

  25. 94CEII#34 100 kW of electrical power is transmitted at 20 kV through cables of total resistance 4 . Find the potential drop and power loss in the cables. By P = V I  I = 100k  20k = 5 A Potential drop in cables = I R = 5 (4) = 20 V Power loss in cables = V I = 20 (5) = 100 W Power loss in cables = I2 R = 52 (4) = 100 W

  26. 96CEII#31 Which of the following devices is not an application of electromagnetic induction? A a transformer B a bicycle dynamo C a magnetic tape playback head  D a moving coil loudspeaker

  27. Energy Loss In Transformer

  28. Class example(P.244#13) (a) i. Resistance = ii.current through the lamp = 2 A iii.Power loss:

  29. iv.Efficiency =

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