Current, resistance and potential difference: Required practical activity 15: use circuit diagrams to set up and check appropriate circuits to investigate the factors affecting the resistance of electrical circuits. This should include:

The idea

In this required practical you build circuits from circuit diagrams and test how resistance depends on factors such as the length of a wire, the number of resistors in series or parallel, and the type of component. A typical method uses a battery or power supply, an ammeter in series, a voltmeter in parallel with the test component, and a variable resistor to change current. Record potential difference and current, then calculate resistance using R = V ÷ I. For a wire, measure resistance at several lengths and plot a graph; resistance should increase with length. For series and parallel combinations, compare measured total resistance with predictions. Control variables such as temperature and wire material. Assess the circuit before closing the switch, check meter ranges and connections, and repeat readings to improve reliability.

What earns the marks

• Draws or follows a circuit diagram with an ammeter in series and a voltmeter in parallel with the component under test.
• Sets up and checks the circuit, including correct meter ranges, secure connections and an open switch before starting.
• Measures current and potential difference and calculates resistance using R = V ÷ I.
• Investigates a named factor, such as wire length, number of resistors or component type, while controlling other variables.
• Records data in a suitable table and plots an appropriate graph, such as resistance against wire length.
• Uses repeat readings or checks anomalous results to improve the reliability of the conclusion.

Common mistakes and how to put them right

• Connecting the ammeter in parallel with the component.

  Put it right: The ammeter must be in series so the current passes through it.

• Connecting the voltmeter in series.

  Put it right: The voltmeter must be in parallel with the component whose potential difference is being measured.

• Changing more than one variable at once, such as wire length and thickness.

  Put it right: Change only the independent variable and keep all others constant.

Exam tips

• Sketch the circuit diagram clearly and label the ammeter, voltmeter and component under test.
• State the independent, dependent and control variables before describing the method.
• Use the equation R = V ÷ I and include units in the results table headings, for example V in volts and I in amperes.