Unit 5 · Electricity and D.C. Circuits

What Cambridge International AS & A Level Physics (9702) Unit 5 covers

Use this map to connect each assessed skill to the relationship or representation that makes it visible.

Electricity and Direct Current Circuits

Connect the published share to the unit model

The 5.50 Ω load and 0.50 Ω internal resistance are in the same current path, giving 6.00 Ω in total. Dividing the 6.00 V e.m.f. by that resistance gives 1.00 A.

Terminal potential difference is lower than e.m.f. while current flows because Ir accounts for 0.50 V inside the source. Circuit topology determines which resistance and potential difference belong in each relation.

The completed chain reports 1.00 A and 5.50 V, then checks that ε = V + Ir. This recovery of the source e.m.f. tests the numerical result.

Mark current directions and potential differences on the circuit before simplifying it. Combine components only where the topology permits, then write the charge, resistance, loop or junction relation symbolically. A final power or limiting-behavior check is useful because it can expose an apparently tidy value obtained from an invalid series or parallel reduction.

The decision that organizes this unit

Define the system and choose the route before calculating

Add 5.50 Ω and 0.50 Ω

Mechanism route and repair branches

Relationships to preserve

• Series path: Load and internal resistance carry the same current.
• Current: The source provides 6.00 V across 6.00 Ω total.
• Terminal p.d.: Internal resistance accounts for Ir.

Representations to read

• A graph of terminal p.d. (V) against current (A).
• A formula card that explains the source relation separates external load resistance from the cell’s internal resistance.
• A table linking key concept, why it matters, visible method.

Branches to reject

• Ignoring r when finding the source current
• Reporting 6.00 V across the load while current flows
• Internal resistance accounts for Ir

How Cambridge International AS & A Level Physics (9702) assesses Electricity and D.C. Circuits

What a complete response must make visible

Match the task to evidence that a reader can audit, then check the most likely reasoning failure before finalizing the response.

Worked example: charge, resistance and circuit networks

Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.

Practice 1: Cell with internal resistance

Practice 2: Potential divider reasoning

Key terms for Unit 5: Electricity and D.C. Circuits

Models, uses, and boundaries

Electricity and Direct Current Circuits

The source relation separates external load resistance from the cell’s internal resistance. Use this relationship when the source relation separates external load resistance from the cell’s internal resistance..

Worked example: charge, resistance and circuit networks

At 1.00 A, the internal drop Ir is 0.50 V and the load receives 5.50 V. Use this relationship when at 1.00 A, the internal drop Ir is 0.50 V and the load receives 5.50 V..

Electricity and Direct Current Circuits: change one condition

Two current coordinates on V = 6.00 − 0.50I compare the cell’s loaded terminal values. Use this relationship when two current coordinates on V = 6.00 − 0.50I compare the cell’s loaded terminal values..

Electricity and Direct Current Circuits: test proposed results

A proposed result should satisfy both ε = I(R + r) and V = ε − Ir. Use this relationship when a proposed result should satisfy both ε = I(R + r) and V = ε − Ir..

Cambridge International AS & A Level Physics (9702) Unit 5 FAQ

Evidence workshop

Continue from the free model into complete practice

The full unit guide continues with the chapter’s worked examples, figures, scoring tables, and answer checks.

• Worked example: charge, resistance and circuit networks
• Electricity and Direct Current Circuits: change one condition
• Electricity and Direct Current Circuits: test proposed results
• Check the worked-example evidence for Electricity and Direct Current Circuits

Related Cambridge International AS & A Level Physics (9702) unit guides

How to study Cambridge International AS & A Level Physics (9702) Unit 5

Start with the organizing decision

Before solving, restate the decision in operational terms: Verify that 5.50 V across the load plus the 0.50 V internal drop recovers the stated 6.00 V e.m.f.. Your first written move should be to Add 5.50 Ω and 0.50 Ω.

Practice the same idea in several representations

Rotate through A graph of terminal p.d. (V) against current (A)., A formula card that explains the source relation separates external load resistance from the cell’s internal resistance., A table linking key concept, why it matters, visible method.. Use each representation to practice Electric Current and Charge Carriers, Potential Difference and Electrical Power, Resistance, Resistivity and I-V Characteristics, Practical Circuits: e.m.f., Terminal Potential Difference and Internal Resistance, Kirchhoff's Laws and Combinations of Resistors, Potential Dividers, Potentiometers, Thermistors and Light-Dependent Resistors, and explain what stays invariant when the surface form changes.

Turn each error into a repair check

After every attempt, audit the response for Ignoring r when finding the source current; Reporting 6.00 V across the load while current flows; Internal resistance accounts for Ir. Then redo only the first step that made the reasoning diverge, keeping units, direction, and model conditions visible.

Confirm current course details in the official Cambridge International syllabus for the 2025-2027 administration.

Where to go next

Return to the Cambridge International AS & A Level Physics (9702) to see every unit and plan your revision.