1.2 Conservation and dissipation of energy

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Question 13

Electric motors used in cargo winches are labelled with a power input.

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

The electrical energy transferred to the motor per second.
The total amount of electric charge passing through the motor.
The rate of change of magnetic flux in the motor coil.
The work done against gravity by the motor per second.

[1]

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

[1]

An electric winch motor has a power input of $W180\text{ W}$ . The operating potential difference is $V24\text{ V}$ . Calculate the current in the motor.

[2]

The table below shows information about three different electric winch motors, P, Q, and R.

Motor	Total power input in watts	Useful power output in watts	Efficiency
P	$100.0$	$85.0$	$0.85$
Q	$250.0$	$100.0$	$0.40$
R	$150.0$	$Z$	$0.72$

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

[1]

Calculate the value of $Z$ 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]

1.2 Conservation and dissipation of energy

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Question 13

Electric motors used in cargo winches are labelled with a power input.

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

The electrical energy transferred to the motor per second.
The total amount of electric charge passing through the motor.
The rate of change of magnetic flux in the motor coil.
The work done against gravity by the motor per second.

[1]

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

[1]

An electric winch motor has a power input of $W180\text{ W}$ . The operating potential difference is $V24\text{ V}$ . Calculate the current in the motor.

[2]

The table below shows information about three different electric winch motors, P, Q, and R.

Motor	Total power input in watts	Useful power output in watts	Efficiency
P	$100.0$	$85.0$	$0.85$
Q	$250.0$	$100.0$	$0.40$
R	$150.0$	$Z$	$0.72$

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

[1]

Calculate the value of $Z$ 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]

1.2 Conservation and dissipation of energy

Question 13

Markscheme

1.2 Conservation and dissipation of energy

Question 13

Markscheme

1.2 Conservation and dissipation of energy

Question 13

1.2 Conservation and dissipation of energy Questions

1.2 Conservation and dissipation of energy

Question 13

1.2 Conservation and dissipation of energy Questions