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240 A.C. mains supply is given to one tr...

240 A.C. mains supply is given to one transformer which draws 0.7 A from it. This transformer is used to operate a bulb having power rating "24 V, 140 W". Then efficiency of this transformer is ......

A

`90%`

B

`80%`

C

`70%`

D

`60%`

Text Solution

Verified by Experts

The correct Answer is:
B
Input power `P_1=VI=240xx0.7`
`therefore` input power `P_1`= 168 W
output power `P_2`= 140 W
`therefore` efficiency of transformer
`=("Output power" (P_2))/("Input power" (P_1))=140/168xx100` = 80%
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KUMAR PRAKASHAN-ALTERNATING CURRENTS -SECTION-D MCQs (DARPAN BASED ON TEXTBOOK)
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  2. A step-up transformer operates on a 230V line and supplies 2A to a loa...

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  3. 240 A.C. mains supply is given to one transformer which draws 0.7 A fr...

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  4. The ratio of primary and secondary turns in a transformer is 1: 200. I...

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  5. The ratio of primary and secondary turns in a transformer is 3:2, if 3...

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  6. If current is not obtained from secondary coil of an ideal transformer...

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  7. If number of turns in primary and secondary coils is increased to two ...

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  8. If for an ideal step-up transformer current in primary is IP and curre...

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  9. A transformer has an efficiency of 80%. It works at 100V and 4kW. If s...

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  10. For step-down transformer value of transformation ratio is ……….

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  11. In a step-up transformer, use of 120 V line provides a potential diffe...

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  12. In a noiseless transformer, an alternating current of 2A is flowing in...

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  13. A low loss transformer has 250 V applied to primary and gives 4.6 V in...

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  14. In an ideal transformer, the voltage is stepped down from 11 kV to 220...

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  15. The ratio of number of turns in primary and secondary coil of a transf...

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  16. The number of turns in primary and secondary of a transformer are 1000...

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  17. A transformer is having 2100 turns in primary and 4200 turns in second...

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  18. Transformer are used in ……….

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  19. A step-up transformer is used on a 120V line to provide a potential di...

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  20. The power is transmitted from a power house on high voltage a.c. becau...

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