CIE A Level Physics
CIE A Level Physics Electricity Exam Questions
Free CIE A Level Physics exam questions for Electricity, with a mark scheme for every pack. Covers electric current, charge carriers, I = Anvq, potential difference, power, resistance, resistivity and I-V characteristics.
Electricity exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
StemUp mark scheme flashcards
A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £10.99View flashcards
About CIE A Level Physics Electricity
Electricity is Topic 9 of the Cambridge International AS & A Level Physics (9702) syllabus. It introduces charge, current, potential difference, e.m.f. and resistance, and explains current in terms of mobile charge carriers. You use I = Anvq, define the volt and the ohm, apply resistivity and interpret I-V characteristics of resistors, filament lamps, diodes, thermistors and light-dependent resistors. This topic is essential for D.C. circuits and later for Capacitance and Alternating currents. Examiners commonly ask for definitions, resistivity calculations and explanations of why a lamp's resistance increases with current.
What you need to know
- Charge and current Current is the rate of flow of charge, I = ΔQ/Δt. Charge is quantised in multiples of e = 1.60 × 10^-19 C. In a conductor I = Anvq, where n is the number density of charge carriers and v the drift speed.
- Potential difference and e.m.f. Potential difference is energy transferred from electrical to other forms per unit charge, V = W/Q. E.m.f. is energy transferred from other forms to electrical per unit charge.
- Power P = VI = I^2R = V^2/R.
- Resistance and resistivity R = V/I and R = ρL/A, where ρ is resistivity in Ω m. Ohm's law applies to a metallic conductor at constant temperature.
- I-V characteristics A metallic conductor at constant temperature gives a straight line through the origin; a filament lamp curves because resistance rises with temperature; a semiconductor diode conducts in one direction above a threshold voltage.
- Sensing components The resistance of a thermistor (NTC) decreases as temperature increases, and the resistance of an LDR decreases as light intensity increases.
Common mistakes in Electricity
- Defining potential difference as energy per unit current. It is energy transferred per unit charge.
- Using the diameter as the radius in R = ρL/A, or forgetting to convert mm^2 to m^2.
- Saying resistance is the gradient of an I-V graph. Resistance is V/I at a point, not the gradient.
- Confusing e.m.f. and potential difference. E.m.f. involves energy transferred to electrical energy; p.d. involves energy transferred from it.
- Explaining a lamp's rising resistance as electrons 'getting tired'. Higher temperature means larger lattice vibrations, so charge carriers collide more often.
Try three Electricity exam-style questions
1. A copper wire of cross-sectional area 1.0 mm^2 carries a current of 2.0 A. The number density of free electrons is 8.5 × 10^28 m^-3. Calculate the drift speed. (3 marks)
Show the mark scheme answer
A = 1.0 × 10^-6 m^2; v = I/(Anq) = 2.0/(1.0 × 10^-6 × 8.5 × 10^28 × 1.60 × 10^-19); v = 1.5 × 10^-4 m s^-1.
2. A wire of length 1.5 m and diameter 0.30 mm is made of a metal of resistivity 4.9 × 10^-7 Ω m. Calculate its resistance. (3 marks)
Show the mark scheme answer
A = π(0.15 × 10^-3)^2 = 7.07 × 10^-8 m^2; R = ρL/A = 4.9 × 10^-7 × 1.5/7.07 × 10^-8; R = 10 Ω (10.4 Ω).
3. Explain the shape of the I-V characteristic of a filament lamp. (3 marks)
Show the mark scheme answer
As current increases the filament temperature increases; lattice ions vibrate more so electrons collide more often; resistance increases so the graph curves towards the V axis (gradient I/V decreases).
Electricity FAQs
What does Cambridge AS & A Level Physics Electricity cover?
It covers charge and current, I = Anvq, potential difference and e.m.f., electrical power, resistance and resistivity, and I-V characteristics of components including thermistors and LDRs.
Which papers is Electricity examined in?
It is an AS Level topic assessed in Paper 1 and Paper 2, and electrical measurements are common in Paper 3 practical tasks.
Which definitions should I learn for Electricity?
Learn precise definitions of current, potential difference, e.m.f., resistance, the volt, the ohm and resistivity, as these are frequently asked for word for word.
