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Post-UTME Physics 2005 Objective Past Questions

All 23 questions from the Post-UTME Screening (Post-UTME) Physics 2005 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.

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Physics 2005 Objective — Question 1

Which of the following is the best known semi-conductor?

  • A. carbon
  • B. Selenium
  • C. Gallium arsenide
  • D. GermaniumCorrect

Explanation

Germanium was the first widely used, well-known semiconductor material.

Physics 2005 Objective — Question 2

The process of adding impurities to a semiconductor is called

  • A. Transmutation
  • B. DopingCorrect
  • C. Polarization
  • D. Hydrolysis

Explanation

Doping is the deliberate addition of impurities to a semiconductor to alter its conductivity.

Physics 2005 Objective — Question 3

In the Celectric motor, which of the following does not apply?

  • A. SpindleCorrect
  • B. Fixed carbon brushes
  • C. Powerful magnetic field
  • D. Sliprings

Explanation

A spindle is not a standard component of an electric motor, unlike carbon brushes, a magnetic field, and slip rings/commutator.

Physics 2005 Objective — Question 4

In the A.C. generator, which of the following does not apply?

  • A. Fixed carbon brushes
  • B. Spindle
  • C. SplitringsCorrect
  • D. Powerful magnetic field

Explanation

An AC generator uses slip rings (not a split-ring commutator, which is a DC generator feature).

Physics 2005 Objective — Question 5

Which of the following law is an application of the law of conservation of energy?

  • A. Maxwell's law
  • B. Lenz's lawCorrect
  • C. Faraday's law
  • D. Fleming's left hand rule

Explanation

Lenz's law (the induced current opposes the change producing it) is a direct consequence of energy conservation.

Physics 2005 Objective — Question 6

The induction coil is a device for generating a

  • A. High voltage from low A.C. source
  • B. low voltage from high D.C. source
  • C. High voltage from a low D.C. sourceCorrect
  • D. low voltage from a low A.C. source

Explanation

An induction coil converts a low DC voltage into a high voltage using mutual induction and an interrupter.

Physics 2005 Objective — Question 7

Which of the following pairs of quantities have equivalent units?

  • A. work done and momentsCorrect
  • B. Energy and momentum
  • C. strain and Young's modulus
  • D. energy and pressure

Explanation

Work done and moment of a force both have the units of force x distance (Nm/Joules).

Physics 2005 Objective — Question 9

A body starts from rest and moves with an acceleration of 8ms^-2 for 10 seconds. Find the distance covered during the 8th second.

  • A. 256m
  • B. 196m
  • C. 120m
  • D. 60mCorrect

Explanation

Distance in nth second = u + a(2n-1)/2 = 0 + 8(15)/2 = 60m.

Physics 2005 Objective — Question 10

One of the limitations of Bohr's model of the atom is that it does not explain

  • A. The stability of the atom
  • B. Variation of the atomic radius
  • C. The line spectra of hydrogen
  • D. The experimental determination of atomic radiusCorrect

Explanation

Bohr's model successfully explains hydrogen's line spectrum and basic stability, but does not offer a means for the experimental determination of atomic radius or account for multi-electron atoms.

Physics 2005 Objective — Question 11

X-rays were discovered by

  • A. Isaac Newton
  • B. Michael Faraday
  • C. Sir J. J. Thompson
  • D. W. RoentgenCorrect

Explanation

X-rays were discovered by Wilhelm Roentgen in 1895.

Physics 2005 Objective — Question 12

Natural radioactivity was discovered by

  • A. Niel Bohr
  • B. Henri BecquerelCorrect
  • C. De Broglie
  • D. Rutherford

Explanation

Henri Becquerel discovered natural radioactivity in 1896.

Physics 2005 Objective — Question 13

The number of atoms of a radioactive substance is initially 8.0x10^16. If the number reduces to 2.0x10^16 in 64 minutes, what is the half-life of the substance?

  • A. 82min
  • B. 16minCorrect
  • C. 8min
  • D. 4min

Explanation

8 to 2 is a reduction to 1/4, i.e. two half-lives, in 64 minutes, giving a half-life of 32 minutes; option B is presented as the closest listed value, flagged for a possible transcription discrepancy.

Physics 2005 Objective — Question 14

An electric lamp has the following markings 230V, 250W. How long would it take the lamp to use one kilo watt-hour when connected to a 230V mains?

  • A. 8.0hr
  • B. 6.0hr
  • C. 4.0hrCorrect
  • D. 2.0hr

Explanation

Time = Energy/Power = 1000Wh/250W = 4.0 hours.

Physics 2005 Objective — Question 15

Which of the following statements is correct about a semi-conductor at room temperature

  • A. The valence band is filled and the conduction band is partly filled
  • B. The valence band is completely filled
  • C. The valence band is almost filled and the conduction band is almost emptyCorrect
  • D. The valence band is empty and the conduction band is filled

Explanation

In a semiconductor at room temperature, the valence band is almost (but not completely) filled, and the conduction band is almost empty.

Physics 2005 Objective — Question 16

Which of the following statements is not correct?

  • A. When ebonite rod is rubbed with wool the ebonite rod acquires a negative charge and wool acquires a positive charge
  • B. When a glass rod is rubbed with silk the glass rod acquires a positive charge while silk acquires a negative charge
  • C. When fur is rubbed with ebonite rod the ebonite rod acquires a positive charge and fur a negative chargeCorrect
  • D. When wool rubbed with a nebonit rod is brought near silk rubbed with a glass rod attraction occurs

Explanation

Rubbing fur on ebonite gives the ebonite a NEGATIVE charge (and fur positive), not a positive charge as stated - making this the incorrect statement.

Physics 2005 Objective — Question 17

Which of the following arrangements gives the electro magnetic radiation in their ascending order of wave length

  • A. Radio waves, ultra violet rays, x-rays, gamma-rays
  • B. gamma-rays, x-rays, ultra violent rays, radio wavesCorrect
  • C. x-rays, gamma-rays, radio waves, ultra violet Rays
  • D. ultra violent rays, gamma-rays, x-rays, radio waves

Explanation

In ascending order of wavelength (shortest to longest): gamma rays, X-rays, ultraviolet rays, radio waves.

Physics 2005 Objective — Question 18

Which of the following statements is not correct about the astronomical telescope under normal adjustment

  • A. The final image is at infinity
  • B. The principal foci of the objective and eye piece coincide
  • C. The final image is at principal focus of the eye pieceCorrect
  • D. The distance between the lenses is equal to the sum of their focal lengths

Explanation

Under normal adjustment, the final image forms at infinity, not at the principal focus of the eyepiece, making this the incorrect statement.

Physics 2005 Objective — Question 19

Which of the following colours gives the least separation when white light is dispersed by a triangular glass prism?

  • A. Red and blue
  • B. Yellow and greenCorrect
  • C. Orange and indigo
  • D. Green and violet

Explanation

Yellow and green are adjacent in the visible spectrum and have the closest refractive indices, giving the least angular separation.

Physics 2005 Objective — Question 20

An object weighs 100N on the earth's surface. Find its weight at a point P with orbital radius 2R [g=10NKg^-1].

  • A. 40.0N
  • B. 35.0N
  • C. 25.0NCorrect
  • D. 20.0N

Explanation

Gravitational field strength falls off as 1/r^2; at radius 2R (double the surface radius), weight = 100/(2^2) = 25.0N.

Physics 2005 Objective — Question 21

A gas occupies a volume of 40cm^3 at a temperature of 27 degrees C, and a pressure of 80cm Hg. What volume does it occupy at 87 degrees C and pressure 120cm Hg?

  • A. 3200cm^3
  • B. 320cm^3
  • C. 32cm^3Correct
  • D. 3.2cm^3

Explanation

Using the combined gas law: V2 = 40 x (360/300) x (80/120) = 40 x 1.2 x 0.667 = 32cm^3.

Physics 2005 Objective — Question 22

A block and tackle system is used to lift a load of 20N through a vertical height of 10.5m. If the efficiency of the system is 40%, how much work is done against friction

  • A. 310.0JCorrect
  • B. 300.0J
  • C. 290.0J
  • D. 200.0J

Explanation

Work output = 20 x 10.5 = 210J. Since efficiency = output/input, input = 210/0.4 = 525J. Work against friction = input - output = 525-210 = 315J (closest listed option A).

Physics 2005 Objective — Question 23

Which of the following statements is correct about a short-sighted girl who does not put on glasses?

  • A. She cannot see near objects clearly
  • B. Rays of light from a distant object are focused behind her retina
  • C. Her eyeball is too short
  • D. Parallel rays of light are focused in front of her retinaCorrect

Explanation

Short-sightedness (myopia) is characterized by parallel rays from distant objects focusing in front of (not on) the retina.

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