JAMB Physics 2018 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 2018 JAMB Physics paper, with answers and explanations. We hold 87 questions from this paper, and the Skolra app has all of them.

JAMB Physics 2018 questions and answers

1.
Palm oil from a bottle flows out more easily after it has been heated because the
1. A
  viscosity of the oil decreases as its temperature rises
  Correct
2. B
  oil expands and becomes heavier
3. C
  surface tension of the oil increases with heat
4. D
  density of the oil increases on heating
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Answer: A
Heating a liquid weakens the intermolecular forces holding it back from flowing, so its viscosity decreases — the oil becomes runnier.
Heating does the opposite of increasing density: the oil expands slightly and becomes very slightly less dense, not heavier, so that option runs backwards.
2.
A 20kg mass is to be pulled up a slope inclined at 300 to the horizontal. If efficiency of the plane is 75%. The force required to pull the load up the plane is J [g=10ms $^{− 2}$ ]
1. A
  150N
2. B
  133.3N
  Correct
3. C
  100N
4. D
  75N
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Answer: B
On a frictionless (100% efficient) slope, the effort needed to pull the load up at constant speed would just be the component of its weight along the slope: mg sinθ = 20 × 10 × sin30° = 100N.
Because the plane is only 75% efficient, more effort than that ideal value is actually needed: effort = 100N / 0.75 = 133.3N.
Using the ideal 100N and forgetting the plane is not perfectly efficient is what gives that smaller, wrong answer.
3.
In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?
1. A
  10V
2. B
  70V
3. C
  30V
4. D
  40V
  Correct
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Answer: D
At resonance in a series RLC circuit, the inductive and capacitive reactances are exactly equal, XL = XC.
Since the same current flows through every component in a series circuit, the voltage across the inductor and the voltage across the capacitor must also be equal — so if VL = 40V, then VC = 40V too.
The 30V across the resistor is not needed at all for this: at resonance VL and VC are always equal to each other, by definition, regardless of what VR happens to be.
4.
The photo cell works on the principle of the
1. A
  piezoelectric effect
2. B
  thermionic emission
3. C
  photoelectric effect
  Correct
4. D
  electromagnetic induction
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Answer: C
A photocell converts light directly into an electric current because photons striking the metal surface knock electrons out of it — this is the photoelectric effect.
Thermionic emission needs heat, not light, to free the electrons, and electromagnetic induction needs a changing magnetic field, so neither fits a device triggered by light falling on it.
5.
If the fraction of the atoms of a radioactive material left after 120years is $\frac{1}{64}$ , what is the half-life of the material? $\frac{1}{64}$
1. A
  20 years
  Correct
2. B
  15 years
3. C
  60 years
4. D
  24 years
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Answer: A
1/64 is exactly (1/2)⁶, meaning the sample has gone through 6 half-lives in the 120 years given.
Half-life = 120 years ÷ 6 = 20 years.
Dividing 120 by 5 instead of 6 (perhaps miscounting how many times 64 halves) is what gives the wrong 24 years.
6.
The process whereby a liquid turns spontaneously into vapour is called
1. A
  condensation
2. B
  sublimation
3. C
  evaporation
  Correct
4. D
  boiling
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Answer: C
A liquid changing to vapour spontaneously, from its surface, at any temperature (not just at its boiling point) is called evaporation.
Boiling, by contrast, only happens at a fixed temperature and involves vapour forming throughout the whole liquid, not just quietly at the surface.
7.
A solid weighs 45N and 15N respectively in air and water. Determine the relative density of the solid
1. A
  0.67
2. B
  1.5
  Correct
3. C
  30
4. D
  3.0
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Answer: B
Upthrust from the water = loss of weight = 45N - 15N = 30N, and by Archimedes' principle this upthrust equals the weight of water displaced.
Relative density = weight of solid / weight of an equal volume of water = 45/30 = 1.5.
Dividing the water reading by the air reading the wrong way round, or forgetting to subtract first, are the usual slips here.
8.
The friction which exist between two layers of liquid in relative motion is called.
1. A
  surface tension
2. B
  cohesion
3. C
  viscosity
  Correct
4. D
  capillarity
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Answer: C
When layers of a moving fluid slide past each other at different speeds, the internal friction resisting that relative sliding is called viscosity.
Surface tension acts only at a liquid's free surface, and cohesion is simply the attraction between like molecules — neither describes friction between moving layers.
9.
A man hears his echo from a nearby hill 2s after he shouted. If the frequency of his voice is 260Hz and the wavelength is 1.29m, how far away is the hill
1. A
  167.7m
2. B
  335.4m
  Correct
3. C
  670.8m
4. D
  502.1m
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Answer: B
The speed of the sound is found from v = fλ = 260Hz × 1.29m = 335.4ms^-1.
The 2s given is the time for the sound to travel to the hill AND back, so the distance to the hill is v × t / 2 = 335.4 × 2 / 2 = 335.4m.
Forgetting to halve the round-trip time is what gives the doubled value, 670.8m.
10.
The force between the molecules of a liquid in contact with that of a solid is?
1. A
  cohesive force
2. B
  adhesive force
  Correct
3. C
  electrostatic force
4. D
  gravitational force
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Answer: B
The attraction between molecules of two DIFFERENT substances — here, the liquid's molecules and the solid's molecules — is called an adhesive force.
Cohesive force is reserved for the attraction between molecules of the SAME substance, such as liquid molecules attracting each other, which is a different pairing from what is described here.

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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JAMB Physics 2018 past questions

JAMB Physics 2018 questions and answers

Practise all 87 questions we hold from the 2018 paper, on a timed CBT screen

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