Electricity: Paper 2 Answering Guide (Form 5 SPM Physics)

Paper 2 at a glance

• Paper 2 carries 100 marks in total

"Define" items from this chapter

One precise sentence each; the unit is part of the definition where there is one.

• Series circuit, A circuit in which components are connected end to end in a single path, so the same current flows through each.
• Parallel circuit, A circuit in which components are connected across common points, providing more than one path for the current, with the same potential difference across each branch.
• Electromotive force, The energy supplied by a source to move one coulomb of charge around a complete circuit; measured in volts (V).
• Internal resistance, The resistance within a source of electromotive force, such as a cell, which causes some energy to be lost inside the source.
• Electrical energy, The energy transferred by an electric current, equal to power multiplied by time; measured in joules (J).
• Electrical power, The rate at which electrical energy is transferred or used (power = potential difference × current); measured in watts (W).

"Explain" items from this chapter

Give the physics reason, not a description. Model answers in one breath:

• What potential difference really is, Potential difference is the energy given to each unit of charge as it moves between two points. It is what pushes current through a component and is measured in volts.
• Why resistors in parallel lower the total resistance, Adding a resistor in parallel opens another path for current to flow. More paths let more current through for the same voltage, so the combined resistance is lower than any single resistor.
• What e.m.f. and internal resistance mean, E.m.f. is the total energy a cell gives each unit of charge. Internal resistance is the cell's own resistance, which uses up some of that energy, so the voltage available to the circuit drops when current flows.

"Calculate" items from this chapter

Formula, substitution with units, answer with unit, and the trap examiners set for each one.

• Q = It, Electric charge, Q = electric charge (C); I = current (A); t = time (s) · Time must be in seconds (convert minutes). Charge is in coulombs.
• V = W / Q, Potential difference, V = potential difference (V); W = work done (energy) (J); Q = charge (C) · W is energy in joules, Q is charge in coulombs. Recall that 1 V = 1 J C⁻¹.
• V = IR (R = V / I), Ohm's law, V = potential difference (V); I = current (A); R = resistance (Ω) · Ohm's law holds only for ohmic conductors at constant temperature. Resistance R = V / I.
• R = R₁ + R₂ + …, Resistors in series, R = total resistance (Ω); R₁ = first resistance (Ω); R₂ = second resistance (Ω) · In series, just add the resistances. The total is larger than any single resistor.
• 1/R = 1/R₁ + 1/R₂ + …, Resistors in parallel, R = total resistance (Ω); R₁ = first resistance (Ω); R₂ = second resistance (Ω) · Take the reciprocal at the end to get R (not 1/R). The total is smaller than the smallest resistor.
• ε = IR + Ir = V + Ir, Electromotive force, ε = electromotive force (e.m.f.) (V); I = current (A); R = external resistance (Ω); r = internal resistance (Ω); V = terminal potential difference (V) · The terminal p.d. V is always less than the e.m.f. because of the 'lost volts' Ir across the internal resistance.
• E = VIt, Electrical energy, E = electrical energy (J); V = potential difference (V); I = current (A); t = time (s) · Time must be in seconds; energy is in joules (1 J = 1 W s). For kWh, use E = Pt with P in kW and t in hours.
• P = VI = I²R = V²/R, Electrical power, P = electrical power (W); V = potential difference (V); I = current (A); R = resistance (Ω) · Pick the form that matches the known quantities. In I²R square the current; in V²/R square the voltage.

Other command words

• Compare, same feature, both cases, one line each, then the physics that links them.
• Suggest / Modify (Section C), one modification, one reason, tied to a named physics principle; repeat for each aspect the question lists.

Where the marks are in this chapter

The 4 content standards of Electricity can each be asked as a definition, an explanation, a calculation or a diagram. We do not predict which will appear, prepare all of them.

• 3.1 Current and Potential Difference
• 3.2 Resistance
• 3.3 Electromotive Force (e.m.f.) and Internal Resistance
• 3.4 Electrical Energy and Power

A three-step answer routine

1. Count the marks: one idea per mark, so a 3-mark explain needs three physics statements.
2. Name the quantity and its symbol before you use it.
3. Re-read the stem for a hidden condition (constant temperature, uniform acceleration, smooth surface).

More Electricity resources

• Chapter overview: Electricity
• Revision Notes
• Common Mistakes
• Practice Questions
• Paper 3 Guide
• Key Terms
• Calculation practice sets

Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)