JAMB Physics 2023 past questions

Checked by the Skolra question team · Last updated 23 October 2026

Ten questions from the 2023 JAMB Physics paper, with answers and explanations. We hold 65 questions from this paper, and the Skolra app has all of them.

JAMB Physics 2023 questions and answers

1. 1.

   The terminals of a battery of emf 24.0 V and internal resistance of 1.0 Ω is connected to an external resistor 5.0 Ω. Find the terminal p.d.

   1. A
      20.0 V
      Correct
   2. B
      19.0 V
   3. C
      4.0 V
   4. D
      24.0 V
   Show answerHide answer

   Answer: A

   Step 1: Find the current in the circuit using I = E / (R + r), where E is the emf, R is the external resistance and r is the internal resistance.

   I = 24.0 / (5.0 + 1.0) = 24.0 / 6.0 = 4.0 A

   Step 2: The terminal p.d. is the voltage available across the external resistor, not the full emf. It is found from V = E − Ir (the emf minus the drop across the internal resistance).

   V = 24.0 − (4.0 × 1.0) = 24.0 − 4.0 = 20.0 V

   As a check, the same value comes from V = IR = 4.0 × 5.0 = 20.0 V, so 20.0 V is correct.

2. 2.

   The near point of a patient's eye is 50.0 cm. What power (in diopters) must a corrective lens have to enable the eye to see clearly an object 25.0 cm away?

   1. A
      +2.0 D
      Correct
   2. B
      -2.0 D
   3. C
      +6.0 D
   4. D
      +4.0 D
   Show answerHide answer

   Answer: A

   The patient's near point is 50.0 cm — without help, nothing closer than that can be brought into focus. To read an object at 25.0 cm, the corrective lens must take that object and form a virtual, upright image of it out at 50.0 cm, the point the eye can actually focus on.

   Using the thin-lens equation with distances in metres and the sign convention that a virtual image (formed on the same side as the object) is negative:

   Object distance: d_o = 0.25 m
   Image distance: d_i = -0.50 m

   1/f = 1/d_o + 1/d_i = 1/0.25 + 1/(-0.50) = 4.0 - 2.0 = 2.0 m⁻¹

3. 3.

   A simple pendulum, has a period of 5.77 seconds. When the pendulum is shortened by 3 m, the period is 4.60 seconds. Calculate the new length of the pendulum

   1. A
      2.25 m
   2. B
      5.25 m
      Correct
   3. C
      3.00 m
   4. D
      8.26 m
   Show answerHide answer

   Answer: B

   For a simple pendulum, the period is given by T = 2π√(L/g), which rearranges to L = gT²/(4π²), taking g = 9.8 m/s².

   First find the original length using T = 5.77 s:
   L₁ = (9.8 × 5.77²) / (4π²) = (9.8 × 33.29) / 39.48 ≈ 8.26 m

   Now find the new length using the shortened period T = 4.60 s:
   L₂ = (9.8 × 4.60²) / (4π²) = (9.8 × 21.16) / 39.48 ≈ 5.25 m

   As a check, L₁ − L₂ ≈ 8.26 − 5.25 = 3.01 m, which agrees with the pendulum being "shortened by 3 m" as stated in the question, confirming that 5.25 m is the correct new length.

4. 4.

   A piano wire 50 cm long has a total mass of 10 g and its stretched with a tension of 800 N. Find the frequency of the wire when it sounds its third overtone note.

   1. A
      800 Hz
      Correct
   2. B
      200 Hz
   3. C
      600 Hz
   4. D
      400 Hz
   Show answerHide answer

   Answer: A

   Step 1 — Find the mass per unit length (μ):
   μ = mass ÷ length = 0.01 kg ÷ 0.5 m = 0.02 kg/m.

   Step 2 — Find the speed of the wave on the wire:
   v = √(T/μ) = √(800 ÷ 0.02) = √40000 = 200 m/s.

   Step 3 — Find the fundamental frequency:
   f₁ = v ÷ (2L) = 200 ÷ (2 × 0.5) = 200 Hz.

   Step 4 — Apply the overtone rule:
   For a wire fixed at both ends, the fundamental is the 1st harmonic, the 1st overtone is the 2nd harmonic, the 2nd overtone is the 3rd harmonic, and the 3rd overtone is the 4th harmonic. So f = 4 × f₁ = 4 × 200 Hz = 800 Hz, which is correct.

5. 5.

   Light of wavelength 589 nm in vacuum passes through a piece of fused quartz of index of refraction n = 1.458. What is the frequency of the light in fused quartz?

   [Speed of light c = $3.00×10^8 ms^{-1}$]

   1. A
      3.49 × 10¹⁴ Hz
   2. B
      2.06 × 10¹⁴ Hz
   3. C
      5.09 × 10¹⁴ Hz
      Correct
   4. D
      7.43 × 10¹⁴ Hz
   Show answerHide answer

   Answer: C

   Key idea: when light travels from one medium into another (e.g. from vacuum into fused quartz), its frequency stays the same. Only the speed and the wavelength change, because v = fλ and both v and λ scale down by the same factor (the refractive index n) as light enters a denser medium — so f is unaffected.

   Therefore the frequency in fused quartz is simply the frequency in vacuum:

   f = c / λ = (3.00×10^8 ms⁻¹) ÷ (589×10⁻⁹ m) ≈ 5.09×10^14 Hz

   The refractive index n = 1.458 is given only to tempt you into an unnecessary (and wrong) calculation — it affects the speed (v = c/n ≈ 2.06×10^8 ms⁻¹) and the wavelength (λₙ = λ/n ≈ 404 nm) inside the quartz, but not the frequency.

6. 6.

   A generator manufacturing company accidentally made an AC generator instead of a DC generator. To fix this error,

   1. A
      the permanent magnet should be replaced with a stronger electromagnet
   2. B
      the slip rings should be replaced with a split-ring commutator
      Correct
   3. C
      the number of turns on the armature coil should be increased to boost the output current
   4. D
      the speed of rotation of the coil should be reduced to steady the output
   Show answerHide answer

   Answer: B

   The only structural difference between an AC generator and a DC generator is how the rotating coil is connected to the external circuit.

   An AC generator uses two continuous slip rings, which simply carry whatever current the coil produces straight out to the circuit — so the current reverses direction every half turn, giving alternating current.

   A DC generator uses a split-ring commutator instead. The split ring automatically swaps the connection to the external circuit at the same instant the current in the coil reverses, so the terminals always see current flowing the same way — a one-directional (though bumpy) direct current.

7. 7.

   A man swung an object of mass 2 kg in a circular path with a rope 1.2 m long. If the object was swung at 120 rev/min, find the tension in the rope.

   1. A
      95 N
   2. B
      190 N
   3. C
      758 N
   4. D
      379 N
      Correct
   Show answerHide answer

   Answer: D

   The rope supplies the centripetal force that keeps the object moving in a circle, so the tension equals T = mω²r.

   First change the speed to revolutions per second: 120 rev/min ÷ 60 = 2 rev/s. The angular velocity is then ω = 2πn = 2π(2) = 4π ≈ 12.57 rad/s, so ω² ≈ 157.9 (rad/s)².

   Now substitute: T = 2 kg × 157.9 × 1.2 m ≈ 379 N, which is correct.

8. 8.

   Which of the following is/are not true about the heat capacity of a substance?

   (i) It is an intensive property
   (ii) Its S.I unit is $jK-1$
   (iii) It is an extensive property
   (iv) Its S.I unit is $jkg-1$

   1. A
      (i) and (ii) only
   2. B
      (ii) and (iii) only
   3. C
      (iii) and (iv) only
   4. D
      (i) and (iv) only
      Correct
   Show answerHide answer

   Answer: D

   Heat capacity is defined as C = Q/ΔT, the quantity of heat required to raise the temperature of a whole given body (not per unit mass) by one kelvin.

   Because it depends on how much of the substance you have, heat capacity is an extensive property — doubling the mass doubles the heat capacity. So the claim that it is an intensive property is false, and the claim that it is an extensive property is true.

   Its S.I unit is correctly J K⁻¹, since it is just heat energy per kelvin rise — no mass term is involved. The unit J kg⁻¹ belongs instead to specific heat capacity (more precisely J kg⁻¹ K⁻¹), which is heat capacity per unit mass and is the intensive version of the quantity.

9. 9.

   The working of the beam balance is based on the principle of

   1. A
      moments
      Correct
   2. B
      upthrust
   3. C
      conservation of energy
   4. D
      floatation
   Show answerHide answer

   Answer: A

   A beam balance is a lever that is free to turn about a central pivot, with a pan of equal distance from the pivot on each side.

   The principle of moments is correct because the beam settles level only when the turning effect (moment) produced by the load on one side equals the turning effect produced by the load on the other side. Since moment = force × distance from pivot, and the distances are equal on a beam balance, equal masses on both pans give equal moments, and the beam balances.

10. 10.

    When a water droplet is placed on a freshly cut piece of wood, it spreads out to form a thin layer because the wood is

    1. A
       porous, so capillary action draws the water into the tiny spaces and along the surface
       Correct
    2. B
       smooth and non-absorbent
    3. C
       a good conductor of heat
    4. D
       coated with a waterproof wax layer
    Show answerHide answer

    Answer: A

    Wood, especially when freshly cut, is porous — it is full of tiny capillary channels (the vessels that once carried sap up the tree). When a water droplet touches this surface, the adhesive force between the water molecules and the wood fibres is greater than the cohesive force holding the droplet together, so the water wets the surface and is drawn sideways and into the pores by capillary action. This is why the droplet flattens out and spreads into a thin layer instead of staying as a rounded bead.

    So the correct reasoning is that the wood's porous structure lets capillarity pull the water out into a thin spreading layer.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

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