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The efficiency of d.c. motor is given by...

The efficiency of d.c. motor is given by `eta =`

A

`("back e.m.f.")/("applied e.m.f.")`

B

`("applied e.m.f.")/("back e.m.f.")`

C

back e.m.f. `xx` applied e.m.f.

D

none of the above

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The correct Answer is:
A
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PRADEEP-ELECTROMAGNETIC INDUCTION & ALTERNATING CURRENT-Exercise
  1. State Fleming's left-hand rule.

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  2. What is the role of the split-ring in an electric motor?

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  3. The efficiency of d.c. motor is given by eta =

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  4. A transformer is an electrical device used for

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  5. The relation (E(s))/(E(P)) = (n(s))/(n(P)) is applicable only be

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  6. A battery of 12 V is connected to primary of a transformer with turns ...

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  7. Out of the following , choose the wrong statement :

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  8. An a.c. generator is a machine that produces…………….from………………

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  9. An a.c generator is based on the phenomenon of……………………………

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  10. In hydroelectric power station,………………of falling water is converted int...

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  11. A d.c. generator produces…………………from…………………

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  12. In d.c. generator,…………………….generator of a.c. generator is replaced by…...

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  13. A d.c. motor converts ………………………into ……………………….

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  14. When a coil carrying current s …………………..it expericences ………………………….whi...

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  15. In a.c. generator, we use……………………… to determine the direction of………………...

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  16. In d.c. motor, we use……………………….to determine the direction of……………………..

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  17. A transformer is an electrical device that is used for …………………. It ………...

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  18. An a.c. generator consists of a coil of 100 turns and cross sectional ...

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  19. An a.c. generator consists of a coil of 2000 turns each of area 80 cm^...

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  20. A flat coil of 500 turns each of area 50 cm^(2) rotates in a uniform m...

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