Quick questions on Power and efficiency explained: O-Level Physics

4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is efficiency in terms of power?

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Because power is energy per second, efficiency can also be written using powers:

What is q1?

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A machine transfers

600\ \text{J}

of energy in

3.0\ \text{s}

. Calculate its power. [2 marks]

What is q2?

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A device takes in

400\ \text{J}

and usefully outputs

240\ \text{J}

. Calculate its efficiency. [2 marks]

What is q3?

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Explain why no device can be more than

100\%

efficient. [2 marks]

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