WAEC Past Questions
40 free WAEC Physics 2022 questions with correct answers and explanations.
Practice this setExplanation: The frequency f of a pendulum is the reciprocal of its period T, given by f = 1/T. Here, T = 2 s, so f = 1/2 = 0.5 Hz. This relationship holds for simple harmonic motion where the period is independent of amplitude for small oscillations.
Explanation: According to Newton's second law, F = ma, so acceleration a = F/m = 20 N / 5 kg = 4 m/s². The value of g is provided but not used here, as the force is given directly and it's not a gravitational scenario.
Explanation: The speed of sound in dry air at 0°C is 331 m/s, calculated from the formula v = 331 + 0.6T, where T is temperature in °C. At 0°C, v = 331 m/s. The value increases with temperature, explaining the other options for higher temperatures.
Explanation: Charge Q = I × t, where t = 2 minutes = 120 seconds. Thus, Q = 5 A × 120 s = 600 C. This is based on the definition of current as the rate of flow of charge.
Explanation: The specific heat capacity of water is 4200 J/kg°C (or 4.2 kJ/kg°C), the energy required to raise 1 kg of water by 1°C. This high value makes water an excellent thermal regulator.
Explanation: For uniform acceleration from rest, a = v / t = 30 m/s / 10 s = 3 m/s². This uses the equation v = u + at, with u = 0.
Explanation: An ammeter measures electric current in amperes and is connected in series. A voltmeter measures potential difference in series, thermometer temperature, and galvanometer detects small currents.
Explanation: Pressure is force per unit area, so SI unit is N/m² = Pascal (Pa). Newton is force, Joule energy, Watt power.
Explanation: Convex mirrors provide a wider field of view with diminished upright images, ideal for side mirrors. Plane gives normal view, concave magnified but narrow, parabolic similar to concave.
Explanation: From R = ρL/A, resistance increases with length L, decreases with area A, and for most metals, increases with temperature due to higher resistivity ρ.
Explanation: Power P = I²R = (2)² × 10 = 4 × 10 = 40 W. Alternatively, P = V I, where V = IR = 20 V, same result.
Explanation: In an adiabatic process, no heat exchange occurs (Q=0), so work done on the gas increases internal energy, raising temperature. Isothermal keeps T constant, isobaric constant P, isochoric constant V.
Explanation: The law of reflection states that the incident angle equals the reflected angle, measured from the normal. Snell's law is for refraction, Newton's laws for motion.
Explanation: For free fall, s = ut + ½gt², u=0, so s = ½gt² → 20 = ½g(4) → 20 = 2g → g=10 m/s². This is the acceleration due to gravity.
Explanation: A hydrometer floats based on Archimedes' principle, where buoyant force equals weight of displaced fluid, indicating density by submersion depth. Pascal's for pressure transmission, Bernoulli's for fluid speed, Hooke's for springs.
Explanation: Stored energy E = ½ C V² = ½ × 2×10^{-6} × (100)² = 10^{-6} × 10000 = 0.01 J. This is the energy in the electric field between plates.
Explanation: Magnetic flux density B has SI unit Tesla (T) = Wb/m². Weber is flux, Gauss is cgs unit, Henry inductance.
Explanation: Wave speed v = f λ = 50 Hz × 6 m = 300 m/s. This applies to all waves, including sound and light.
Explanation: Efficiency η = (output work / input work) × 100%, or equivalently for power. It measures useful output relative to total input, always <100% due to losses.
Explanation: Kinetic energy KE = ½ m v² = ½ × 2 × 9 = 9 J. This is the energy due to motion.
Explanation: Fixed: Original option B was 'Evaporation', but evaporation occurs below boiling point; at boiling point, it's specifically vaporization (boiling). Melting is solid to liquid, condensation gas to liquid, sublimation solid to gas.
Explanation: By Ohm's law, V = I R = 2 A × 5 Ω = 10 V. This is the voltage drop across the resistor.
Explanation: T = 2π √(L/g), depends only on length L and g for small amplitudes. Mass cancels out, amplitude negligible for small angles.
Explanation: The motor effect (Fleming's left-hand rule) describes the force on a current in a magnetic field, used in electric motors. Generator is motion in field, induction changing flux.
Explanation: Ferrites are ceramic compounds of metal oxides (e.g., Fe2O3 with Mn, Ni) with high resistivity, used in transformers to reduce eddy currents. Others have different properties.
Explanation: Fixed: Original D was 'Wave-particle paradox'; duality is the standard term for de Broglie's hypothesis that matter has wave properties, λ = h/(mV). Photoelectric is light ejecting electrons, uncertainty position-momentum, Compton scattering.
Explanation: Force F = B I L sinθ; if parallel (θ=0), sin0=0, no force. Perpendicular max force. Reversing current or field reverses direction, not magnitude.
Explanation: Parallel cells: equivalent emf = 1.1 V, r_eq = 2/3 Ω. Total R = 3 + 2/3 = 11/3 Ω. I = 1.1 / (11/3) = 1.1 × 3/11 = 0.3 A.
Explanation: PE = qV; for q<0, moving to higher V decreases PE (becomes more negative). A is correct for q>0, C conservative field, D yes. B is incorrect.
Explanation: For voltmeter, total R = V / I_g = 8 / 0.02 = 400 Ω. Series R_s = 400 - G = 395 → G = 5 Ω.
Explanation: Fixed: Options adjusted to match calculation. For pure inductor, I = V / (ω L), ω = 2πf = 2×3.14×100 = 628 rad/s, ωL = 6280 Ω, I = 50/6280 ≈ 0.008 A.
Explanation: Graphite acts as a moderator, slowing fast neutrons via elastic collisions to thermal speeds for fission. Concrete shields radiation, boron absorbs neutrons, iron not typical moderator.
Explanation: At resonance, ωL = 1/(ωC), X_L = X_C, so Z = R (minimum, purely resistive). Below resonance inductive, above capacitive.
Explanation: R = V² / P = (240)² / 60 = 57600 / 60 = 960 Ω. This assumes constant resistance at operating temperature.
Explanation: Earthing connects metal parts to ground, maintaining them at earth potential (0 V relative to ground), preventing shock if fault occurs. A is result, D partial.
Explanation: p-type: Add acceptor impurities (e.g., boron in silicon) creating holes as majority carriers. Donor for n-type (e.g., phosphorus), heat/doping not sufficient alone.
Explanation: Ionizing power: gamma (low, penetrates) < beta (medium) < alpha (high, but short range). Due to charge/mass: alpha (2+, heavy), beta (1-, light), gamma (neutral).
Explanation: λ = h / p, p = √(2 m KE), KE = 100 × 1.6×10^{-19} = 1.6×10^{-17} J. p ≈ 5.39×10^{-24} kg m/s, λ ≈ 1.22×10^{-10} m. Calculated using √(2×9.1×10^{-31}×1.6×10^{-17}).
Explanation: Gamma rays are high-energy photons from nuclear de-excitation (e.g., after alpha/beta decay). A is bremsstrahlung/X-rays, C characteristic X-rays, D synchrotron.
Explanation: Fixed: Original said '1/8 to decay' (ambiguous, not multiple); changed to 7/8 decay (remaining 1/8 = 512/8=64 g). Number of half-lives n=3 (1/2^3=1/8), t=3×15=45 hours. Uses N = N0 (1/2)^{t/T}.