WJEC A Level Physics
WJEC A Level Physics Unit 2: Electricity and Light Exam Questions
Free WJEC A Level Physics exam questions for Unit 2: Electricity and Light, with a mark scheme for every pack. Covers Current and drift velocity, resistance and resistivity, d.c. circuits and internal resistance, waves, interference, refraction, photons and lasers.
Unit 2: Electricity and Light exam questions
7 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.
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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.
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About WJEC A Level Physics Unit 2: Electricity and Light
Unit 2 of WJEC A Level Physics, Electricity and Light, is the second AS unit. It covers conduction and drift velocity, resistance, resistivity and superconductivity, d.c. circuits including potential dividers and internal resistance, the nature and properties of waves with interference, diffraction and stationary waves, refraction and optical fibres, photons with the photoelectric effect and energy levels, and how lasers work. It prepares you for capacitance in Unit 4. Examiners regularly test resistivity and internal resistance practicals, Young's double slit and grating calculations, total internal reflection and the photoelectric equation.
What you need to know
- 2.1 Current as rate of flow of charge, the drift velocity equation I = nAve, and potential difference as energy per unit charge.
- 2.2 Ohm's law, I-V characteristics, resistivity R = rho l / A, the variation of resistance with temperature in metals, and superconductivity below the critical temperature.
- 2.3 Series and parallel circuits, conservation of charge and energy, potential dividers, and EMF and internal resistance V = E - Ir.
- 2.4-2.5 Transverse and longitudinal waves, polarisation, diffraction, Young's double slit lambda = a Delta y / D, diffraction gratings d sin(theta) = n lambda, and stationary waves with nodes and antinodes.
- 2.6 Refractive index, Snell's law, total internal reflection and critical angle, and multimode dispersion in optical fibres and how monomode fibres reduce it.
- 2.7 and 2.8 Photon energy E = hf, the photoelectric effect with Einstein's equation, line spectra and energy levels, ionisation, and lasers based on population inversion and stimulated emission, including semiconductor lasers.
Common mistakes in Unit 2: Electricity and Light
- Saying the drift velocity of electrons is very fast. Drift velocity is typically less than a millimetre per second; the signal travels quickly but electrons move slowly.
- Claiming superconductors have very low resistance. Below the critical temperature their resistance is zero.
- Writing that stimulated emission produces a photon in a random direction. The emitted photon has the same frequency, phase, direction and polarisation as the stimulating photon.
- Using fringe spacing measured over several fringes as one spacing. Divide the total distance by the number of fringe gaps.
- Saying polarisation proves light is longitudinal. Only transverse waves can be polarised, so polarisation shows light is transverse.
Try three Unit 2: Electricity and Light exam-style questions
1. A wire of length 1.5 m and cross-sectional area 2.0 x 10^-7 m2 has resistivity 4.9 x 10^-7 ohm m. Calculate its resistance. (2 marks)
Show the mark scheme answer
R = rho l / A = 4.9 x 10^-7 x 1.5 / 2.0 x 10^-7; = 3.7 ohm.
2. In a double slit experiment, slit separation is 0.50 mm, slit-screen distance is 2.0 m and fringe spacing is 2.4 mm. Calculate the wavelength. (2 marks)
Show the mark scheme answer
lambda = a Delta y / D = 0.50 x 10^-3 x 2.4 x 10^-3 / 2.0; = 6.0 x 10^-7 m.
3. Explain why a population inversion is needed for laser action. (3 marks)
Show the mark scheme answer
Normally more electrons are in the lower level so absorption dominates; with more electrons in the upper level stimulated emission is more likely than absorption; giving light amplification as photons trigger further emissions.
Unit 2: Electricity and Light FAQs
What does WJEC A Level Physics Unit 2: Electricity and Light cover?
Conduction of electricity, resistance, d.c. circuits, the nature and properties of waves, refraction of light, photons and lasers.
Is Unit 2 an AS or A2 unit?
Unit 2 is an AS unit assessed by a written exam.
Which practicals are linked to Electricity and Light?
Common ones include determining resistivity, measuring internal resistance, finding the wavelength of light with a double slit or grating, and measuring refractive index.
