Three and four mark questions

These are similar to one and two mark questions but you will be expected to write in more depth for three and four mark questions.

Three and four mark questions usually require longer answers.

Edexcel questions courtesy of Pearson Education Ltd.

Sample question 1 - Foundation and Higher


A student uses this circuit to investigate how the current in a filament lamp varies with the potential difference (voltage) across the lamp:

Circuit with a battery, variable resistor, ammeter and a lamp.

The student takes a range of measurements for the filament lamp.

He plots this graph from his measurements:

Graph plotting potential difference against current, the curve slopes upwards for a while, but then levels out and continues upwards but at a lower gradient.

Explain how changes in the filament of the lamp account for this graph. [4 marks]

The resistance of the lamp is constant up to 3 V [1]. It is:

R = \frac{V}{I}

= \frac{3}{0.3}

= 10 \Omega [1]

Then as the filament becomes hotter, its resistance increases [1]. This means the current is lower, and the gradient of the line becomes less steep [1].

Sample question 2 - Foundation and Higher


Explain why the temperature of a resistor increases when a current passes through it. [3 marks]

Current is a flow of electrons [1]. The electrons collide with ions in the metal [1], transferring energy into the thermal store of the resistor [1].

Sample question 3 - Foundation and Higher


A kettle is earthed and fitted with a fuse. Explain how this can protect the person using the kettle if there is a fault. [3 marks]

When there is a fault that causes a large current to flow through the earth wire, the fuse melts/blows [1]. This breaks the circuit [1] and prevents a person from getting an electric shock if they touch the kettle [1].