4.2.2.1 Circuits

Spec reference: 4.2.2 (subtopic).

What you need to know

• Circuits with Resistors
• Independent variable: circuit type (series, parallel).
• Dependent variable: resistance.
• Control variables: number of resistors, type of power
• source.
• Conclusion: Adding resistors in series increases the total
• resistance of the circuit. In a parallel circuit, the more
• resistors you add, the smaller the resistance.

Self-assessment (checklist)

• I can state the two ways of joining electrical components
• I can describe the current through components
• I can describe the potential difference across components
• I can describe the total resistance of two components
• I can describe the potential difference across components
• I can describe the current through components
• I can describe the total resistance of two components
• I can use circuit diagrams to construct and check series
• I can describe the difference between series and parallel
• I can explain qualitatively why adding resistors in series
• I can explain the design and use of dc circuits for
• I can calculate the currents, potential differences and
• I can solve problems for circuits which include resistors in

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.