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Electric motors used in water pumps are labelled with a power input.

What does the power input of a motor mean? Select one explanation from the list below:

The electrical charge transferred by the motor per second.
The electric current flowing through the motor.
The electrical energy transferred each second to the motor.
The electrical potential difference across the motor.

[1]

Write down the equation which links current, potential difference, and power.

[1]

A utility pump's electric motor has a power input of $W75\text{ W}$ . The power supply potential difference is $V12\text{ V}$ . Calculate the current in the motor.

[2]

The table below shows information about three different electric motors, A, B, and C.

Motor	Total power input in watts	Useful power output in watts	Efficiency
A	$50.0$	$40.0$	$0.80$
B	$120.0$	$30.0$	$0.25$
C	$80.0$	$Y$	$0.65$

Write down the equation which links efficiency, total power input, and useful power output.

[1]

Calculate the value of $Y$ in the table.

[2]

In addition to the total power input, electric motors should also be labelled with their efficiency or their useful power output. Suggest why.

[2]

Conservation and dissipation of energy Questions

Practise AQA GCSE Physics Conservation and dissipation of energy with exam-style questions for Foundation and Higher tier. 29 questions covering Energy transfers in a system and Efficiency, matched to the AQA GCSE Physics (8463) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.