The efficiency of a transformer which draws a power of 20 watt is 60%, the power supplied by it is:
Correct answer: D. 12 W
- A. 5 W
- B. 1.2 W
- C. 6 W
- D. 12 W
Explanation
The formula for efficiency is:% Efficiency = (Total Power Output/Total Power Input) x 100So if power input is 20 W, and % Efficiency is 60% we can rearrange the formula to make Power Output the subject and get the answer 12 W.
This question appeared on the ETEA MDCAT 2015 paper, which you can sit online with every answer explained.
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About Transformers
Transformers transfer alternating electrical energy between coils by mutual induction, with voltage ratio determined by the turns ratio. The topic covers step-up and step-down transformers, current changes, ideal power conservation and practical losses such as heating and flux leakage. A transformer requires changing magnetic flux, so it does not operate with steady direct current.
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