Questions on Electric Circuits
Q14. Gary uses the following circuit to operate the electric motor of his model crane. Look carefully at the way Gary has connected the two cells.
![](electricitydiagram14c.png)
When he closes switch A the motor runs and the crane lifts a load.
(a) Gary opens switch A and closes switch B. Describe what happens to the motor.
The motor turns in the opposite direction - goes into reverse mode. ![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
(b) Gary closes both switches, A and B. Describe what happens to the motor.
It stops turning. ![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
(c) Both switches should not be closed at the same time. Explain why.
- the batteries or cells or wires will get hot
OR
- the batteries or cells will go flat quickly
![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
(d) Gary puts a resistor into his circuit as shown.
![](electricitydiagram14b.png)
What difference does the resistor make to the motor:
(i) when switch A is closed and switch B is open?
The motor turns forward just as it did before. ![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
(ii) when switch A is open and switch B is closed?
The motor turns in reverse mode - be more slowly than before.![](../../../graphics/symbols/nuclides/ticksmall.png)
1 mark
Maximum 5 marks
![](../../../graphics/buttons/Clickhereforsolution.png)