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Question 5

An electric winch is labelled with its power input.

What does power input mean?

Select one option:

The electrical charge transferred each second through the winch motor.
The electrical energy transferred each second to the winch motor.
The average potential difference across the winch motor.
The electrical current flowing through the winch motor.

[1]

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

[1]

An electric winch motor has a power input of $\text{ W}$ . The mains potential difference is $\text{ V}$ .

Calculate the current in the winch motor. Round your answer to 2 significant figures.

[3]

Table 1 shows information about three different electric winches.

Electric winch	Total power input in watts	Useful power output in watts	Efficiency
P	300	240	0.80
Q	1200	900	0.75
R	800	$k$	0.72

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

[1]

Calculate the value of $k$ in Table 1.

[2]

In addition to power input, electric winches should also be labelled with their useful mechanical power output. Suggest why this is important for a consumer.

[2]

An electric winch is labelled with its power input.

What does power input mean?

Select one option:

The electrical charge transferred each second through the winch motor.
The electrical energy transferred each second to the winch motor.
The average potential difference across the winch motor.
The electrical current flowing through the winch motor.

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

[1]

An electric winch motor has a power input of $\text{ W}$ . The mains potential difference is $\text{ V}$ .

Calculate the current in the winch motor. Round your answer to 2 significant figures.

[3]

Table 1 shows information about three different electric winches.

Electric winch	Total power input in watts	Useful power output in watts	Efficiency
P	300	240	0.80
Q	1200	900	0.75
R	800	$k$	0.72

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

[1]

Calculate the value of $k$ in Table 1.

[2]

In addition to power input, electric winches should also be labelled with their useful mechanical power output. Suggest why this is important for a consumer.

[2]

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Question 5

Markscheme

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Question 5

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1 Energy

Question 5

1 Energy Questions