C8ElectricCurrentPotentialDifferenceandResistance

What are the definitions of potential difference (p.d.) and electromotive force (e.m.f.), in terms of

energy transfer W and charge q ?

• A

• B

• C

• D

A resistor dissipates 25 W of power when there is a potential difference (p.d.) of 4.0 V across it.

What is the resistance of the resistor?

• 0.16 Ω

• 0.64 Ω

• 100 Ω

• 400 Ω

A kettle is connected to a 250 V mains supply.

What are possible values for the power of the kettle and the current in the kettle?

• A

• B

• C

• D

A cell with internal resistance is connected to a variable resistor R as shown.

The resistance of R is gradually decreased.

How do the current I and the terminal potential difference (p.d.) across the cell change?

• A

• B

• C

• D

What is the definition of potential difference across a component?

• energy transferred per unit charge

• energy transferred per unit current

• energy transferred per unit distance

• energy transferred per unit time

The I–V characteristics for four components, A, B, C and D, are shown.

Which component has the greatest resistance when the potential difference across it is V1?

• A

• B

• C

• D

Which quantity is given by the product of charge and electric potential difference?

• current

• energy transferred

• power dissipated

• resistance

The current in a filament lamp is increased.

Which statement about the lamp is correct?

• The brightness of the lamp decreases.

• The potential difference across the filament decreases.

• The resistance of the filament decreases.

• The temperature of the filament increases.

The current I in a conductor is given by the equation shown.

I = Anvq

What does the letter n represent in this equation?

• charge carried per charge carrier

• number of charge carriers per unit area

• number of charge carriers per unit volume

• total mass of charge carriers per unit volume

Which graph could show how the resistance R of a filament lamp varies with the applied potential

difference (p.d.) V, as V is increased to the normal operating p.d.?

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