International A LevelPhysicsEdexcelExam Questions2. Waves & ElectricityResistance, Resistivity & Potential Dividers

Resistance, Resistivity & Potential Dividers (Edexcel International A Level Physics)

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Resistance, Resistivity & Potential Dividers

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Resistance, Resistivity & Potential Dividers

1a
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Two copper wires, W and Z, are joined as shown. Wire W has twice the diameter of wire Z.

q11-wph12-02-june-2021-edexcel-int-as-a-level-phy

W and Z are connected in series with a cell and resistor, as shown.

q11-1-wph12-02-june-2021-edexcel-int-as-a-level-phy

State the purpose of the resistor in this circuit.

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1b
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The current I in a conductor is given by the formula

            I space equals space n q v A

Complete the following table, which shows ratios of quantities for wires W and Z.
The first row has been completed for you.

Ratio Value Reason
n subscript w over n subscript z 1 Both wires are made of the same material
I subscript w over I subscript z    
v subscript w over v subscript z    

  

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2a
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A filament lamp is marked 12 V 60 W. The filament is made from a long metal wire with a diameter of 0.25 mm. The metal has a resistivity of 5.6 × 10−8 Ω m when the wire is at normal operating temperature.

Calculate the length of the wire in the filament.






Length of wire = .........................................

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2b
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A student has two filament lamps. Lamp A is marked 12 V 60 W and lamp B is marked 12 V 30 W. The student sets up the circuit shown.

q13b-wph12-02-oct-2021-edexcel-int-as-and-a-level-phy

The student states that both lamps will operate normally.

Evaluate whether the student’s statement is correct.

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3a
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A nichrome wire of length 0.45 m has a cross-sectional area of 2.5 × 10–7 m2.
The resistance of the wire is 2.0 Ω.

Calculate the resistivity of nichrome.




Resistivity = ...................................

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3b
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A potential difference of 3.0 V is applied across the nichrome wire.

Calculate the drift velocity of the conduction electrons in the nichrome wire.

number of conduction electrons per m3 = 9.0 × 1028 m–3





Drift velocity = .................................

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3c
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A student suggests that the drift velocity will double if the length of wire used in the circuit is halved.

Comment on this suggestion.

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