JAMB Physics 2019 past questions

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

Ten questions from the 2019 JAMB Physics paper, with answers and explanations. We hold 73 questions from this paper, and the Skolra app has all of them.

JAMB Physics 2019 questions and answers

1. 1.

   The volume of a stone having an irregular shape can be determined using?

   1. A
      a measuring cylinder and water, by the displacement method
      Correct
   2. B
      a beam balance and a density bottle without liquid
   3. C
      a vernier caliper and a micrometer screw gauge
   4. D
      a metre rule and a spring balance
   Show answerHide answer

   Answer: A

   An irregularly shaped object like a stone has no simple formula for its volume, so the displacement method using a measuring cylinder (or Eureka can) and water is used. The stone is lowered into a known volume of water, and the rise in water level gives the volume of the stone directly (Volume of stone = final reading − initial reading).

2. 2.A mass of 0.5kg is whirled in a vertical circle of radius 2m at a steady rate of 2 rev/s. Calculate the centripetal force
   1. A
      316 N
   2. B
      158 N
      Correct
   3. C
      12.6 N
   4. D
      4 N
   Show answerHide answer

   Answer: B

   The centripetal force formula is F = mω²r, where ω is the angular speed in rad/s.

   First convert the rate of revolution to angular speed: ω = 2πf = 2π × 2 rev/s = 4π rad/s ≈ 12.57 rad/s.

   Then F = mω²r = 0.5 kg × (12.57)² × 2 m = 0.5 × 157.9 × 2 ≈ 158 N.

   A candidate who forgets to convert the frequency to angular speed and simply squares the 2 rev/s figure gets 0.5 × 2² × 2 = 4 N — much too small, because rev/s is not the same as rad/s.

   A candidate who mistakes radius for diameter (using 4 m instead of 2 m) doubles the correct answer to about 316 N.

3. 3.

   The earth's gravitational field intensity at its surface is about

   (G = 6.7 × 10$^{-11}$Nm$^2$/kg$^2$, mass of the earth is 6 × 10$^{24}$kg, radius of the earth is 6.4 × 10$^6$m, g on the earth = 9.8m/s$^2$)

   1. A
      9.5N/kg
   2. B
      8.6N/kg
   3. C
      9.8N/kg
      Correct
   4. D
      10.2N/kg
   Show answerHide answer

   Answer: C

   The gravitational field intensity at the earth's surface is given by g = GM/r².

   Substituting the values: g = (6.7 × 10^-11 × 6 × 10²⁴) / (6.4 × 10⁶)²

   Numerator = 6.7 × 6 × 10¹³ = 4.02 × 10¹⁴

   Denominator = (6.4)² × 10¹² = 4.096 × 10¹³

   g = 4.02 × 10¹⁴ / 4.096 × 10¹³ ≈ 9.8N/kg, which agrees with the g on the earth given in the question (9.8m/s²), confirming the correct value.

   A candidate who rounds the numerator or denominator early, or who mis-squares the radius, can drift to 9.5N/kg or 10.2N/kg. Using the wrong power of ten in the radius squaring step gives a low value like 8.6N/kg.

4. 4.

   An a.c of 1A at a frequency of 800 cycles per second flows through a coil, the inductance of which is 2.5mH and the resistance of which is 5Ω. What is the power absorbed in the Coil?

   1. A
      13.5W
   2. B
      5W
      Correct
   3. C
      2.5W
   4. D
      12.5W
   Show answerHide answer

   Answer: B

   In an a.c. circuit containing resistance and inductance in series, the inductor absorbs no net power — it only stores energy in its magnetic field and returns it every cycle. Only the resistive part of the coil actually dissipates energy as heat.

   True power absorbed: P = I²R = (1)² × 5 = 5W.

   The distractor of 12.5W comes from mistakenly using only the reactance (XL = 2πfL = 2π×800×2.5×10⁻³ ≈ 12.57Ω) as if it dissipated power. The 13.5W distractor comes from using the impedance Z = √(R²+XL²) ≈ 13.53Ω in place of R — confusing apparent power (I×V, using Z) with real power (which only uses R). The 2.5W distractor comes from an arithmetic slip, halving I²R by mistake.

5. 5.

   Heat may be transferred by conduction, convention and radiation. By which of these methods does heat travel through vacuum?

   1. A
      Convention
   2. B
      Conduction
   3. C
      Radiation
      Correct
   4. D
      Conduction and convection
   Show answerHide answer

   Answer: C

   Radiation is the correct method. Heat radiation travels as electromagnetic waves, so it does not need any particles of matter to carry it — that is exactly how heat from the sun reaches the earth through empty space.

   Conduction needs vibrating particles passing energy from one to the next, so it only works in solids (and to a lesser extent liquids/gases) where particles are in contact. Convection needs a fluid whose particles can physically move and carry heat with them. Since a vacuum has no particles at all, neither conduction nor convection can occur there, which rules out both "conduction" and "conduction and convection" as answers.

6. 6.

   Water and Kerosine are drawn respectively into the two limbs of a Hare's apparatus. The destiny of water is 1.0gcm$^{-3}$ and the density of kerosine is 0.80gcm$^{-3}$. If the height of the water column is 20.0cm, calculate the height of the kerosine column.

   1. A
      25.0cm
      Correct
   2. B
      18.0cm
   3. C
      22.5cm
   4. D
      16.0cm
   Show answerHide answer

   Answer: A

   In Hare's apparatus, air is partially evacuated from a T-tube connected to two limbs dipping into water and kerosine. The same reduced pressure acts on both liquid surfaces, so the two columns balance according to ρ₁h₁ = ρ₂h₂, where the pressures produced by each liquid column above the reservoir level must be equal.

   Given: density of water = 1.0 g/cm³, height of water column = 20.0cm, density of kerosine = 0.80 g/cm³.

   ρ_water × h_water = ρ_kerosine × h_kerosine
   1.0 × 20.0 = 0.80 × h_kerosine
   h_kerosine = 20.0 ÷ 0.80 = 25.0cm

   The less dense liquid (kerosine) must rise higher to produce the same pressure as the denser water, so 25.0cm is correct.

7. 7.

   A microscope is focused on a mark on a table, when the mark is covered by a plate of glass 2 cm thick, the microscope has to be raised 0.67cm for the mark to be once more in focus. Calculate the refractive index.

   1. A
      1.50
      Correct
   2. B
      2.99
   3. C
      1.99
   4. D
      1.33
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   Answer: A

   When a glass slab is placed over a mark, the mark appears to shift upward (nearer the observer) by an amount d, and the microscope must be raised by exactly d to refocus. The refractive index formula for this situation is:

   n = t / (t − d)

   where t is the real thickness of the glass (2 cm) and d is the distance the microscope is raised (0.67 cm).

   n = 2 / (2 − 0.67) = 2 / 1.33 ≈ 1.50, which is correct — this matches the known refractive index of ordinary glass.

8. 8.

   When water is boiling, it

   1. A
      absorbs no heat because it has reached its highest possible temperature
   2. B
      releases heat to the surroundings as it turns into vapour
   3. C
      changes state at a temperature that keeps rising with more heating
   4. D
      absorbs heat while its temperature stays constant until it has all turned to vapour
      Correct
   Show answerHide answer

   Answer: D

   When a liquid is boiling, its temperature stays constant even though heat is still being supplied. This is because the heat energy is being used entirely as latent heat of vaporisation, to break the intermolecular bonds and change the water from liquid to vapour, rather than to raise its temperature (kinetic energy of the particles). Once all the liquid has turned to vapour, the temperature can then begin to rise again (if heating continues, as superheated steam).

9. 9.The lead-acid accumulator consists of
   1. A
      carbon rod and zinc casing packed in ammonium chloride paste
   2. B
      lead plates immersed in dilute sulphuric acid
      Correct
   3. C
      lead plates immersed in concentrated sulphuric acid
   4. D
      copper and zinc plates dipped in dilute sulphuric acid
   Show answerHide answer

   Answer: B

   The lead-acid accumulator is a secondary (rechargeable) cell. It is made of lead plates — one plate coated with lead(IV) oxide (PbO₂) as the positive electrode and spongy lead (Pb) as the negative electrode — immersed in dilute sulphuric acid as the electrolyte.

10. 10.

    The part of the human eye that does similar work as the diaphragm of a camera lens is the

    1. A
       Iris
       Correct
    2. B
       Pupil
    3. C
       Retina
    4. D
       Cornea
    Show answerHide answer

    Answer: A

    In a camera, the diaphragm is the adjustable structure that widens or narrows to control how much light enters the lens.

    In the human eye, the iris does exactly this job: it is the coloured muscular ring that contracts or relaxes to change the size of the pupil, thereby controlling the amount of light let into the eye. This makes the iris the eye's equivalent of a camera's diaphragm.

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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