4.2.3.1 Difference

Spec reference: 4.2.3 (subtopic).

What you need to know

• difference/volts (V).
• Dependent variable: current (A).
• Control variable: number of components (e.g. 1 filament
• bulb, 1 resistor), type of power source.
• Set up the circuits as shown below and measure the
• current and the potential difference.
• Draw graphs of the results once collected.
• Equations and Maths

Self-assessment (checklist)

• I can state whether mains electricity is an ac or dc supply.
• I can recall the frequency of the UK mains electricity
• I can recall the potential difference of the UK mains
• I can explain the difference between direct and

Key steps (method)

• Identify what the question is testing and use the correct equation/definition.
• Show substitutions and units clearly.

Common mistakes

• Unit conversions, rearranging errors, or quoting a law without applying it.