Current, Potential Difference, Resistance & Power (Edexcel International A Level Physics)

Topic Questions

1a
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3 marks

The circuit diagram shows a resistor of resistance 270 Ω connected to a battery of e.m.f. 9.0 V. The battery has an internal resistance of 15 Ω.

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Explain why the reading on the voltmeter is less than 9.0 V when the switch is closed.

1b
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3 marks

Calculate the reading on the voltmeter when the switch is closed.




Reading on voltmeter = ..............................

1c
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2 marks

The switch remains closed and 12 C of charge flows through the battery.

Calculate the decrease in the chemical energy store of the battery.



Decrease in chemical energy store = ...........................

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1a
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3 marks

Two resistors of resistance R subscript 1 and R subscript 2 are connected in parallel in a circuit.

Derive a formula for the total resistance R subscript straight T of the combination.

1b
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3 marks

The diagram shows a combination of five resistors, M, N, O, P and Q. Each resistor has a resistance of 5.0 Ω.

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i)
Show that the resistance between points A and B is about 3 Ω.
(3)
ii)
A student is told to modify the combination of resistors so that the combined resistance between A and B is greater than 5.0 Ω. She cannot change the arrangement of the resistors, but she can replace one of the 5.0 Ω resistors with a 20.0 Ω resistor.

Explain, without further calculations, which of the five resistors should be replaced.
(2)

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2a
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3 marks

The circuit diagram shows three identical resistors and two switches, X and Y.
The battery has negligible internal resistance.

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Each resistor consists of a wire of diameter 0.181 mm and length 55.0 cm. At room temperature, the resistivity of the wire is 1.10 × 10−6 Ω m.

Show that the resistance of one resistor at room temperature is about 24 Ω.

2b
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4 marks

A student suggests that the maximum power output from the resistors in this circuit will be greater than 12 W.

Assess whether the student’s suggestion is correct.

2c
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6 marks

Switch X was open and switch Y was closed.

i)
Calculate the number of conduction electrons passing through the resistor every second immediately after switch Y was closed.

(3)




Number of electrons = ............................

ii)
After switch Y had been closed for a few minutes, the power dissipated by the resistor decreased.

Explain why.

(3)

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3a
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6 marks

A student set up the circuit shown.

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Calculate the number of electrons passing point X each second.







Number of electrons in one second = ..............................

3b
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4 marks
Another resistor, Y, is added to the circuit as shown.

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The student wrote the following statement.

When resistor Y is added, the resistance of the parallel section
increases, the resistance of the whole circuit increases, and so, by
P = I2R, the power dissipated by the whole circuit also increases.



Evaluate the student’s statement.

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