JAMB Physics 2013 Objective Past Questions

All 50 questions from the Joint Admissions and Matriculation Board (JAMB) Physics 2013 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.

Physics 2013 Objective — Question 1

Which Question Paper Type of Physics is given to you?

• A. Type DCorrect
• B. Type I
• C. Type B
• D. Type U

Explanation

The question paper type is D.

Physics 2013 Objective — Question 2

When a brick is taken from the earth's surface to the moon, its mass

• A. remains constantCorrect
• B. reduces
• C. increases
• D. becomes zero

Explanation

The mass of an object is constant while its weight varies from place to place.

Physics 2013 Objective — Question 3

The resultant of two forces is 50N. If the forces are perpendicular to each other and one of them makes an angle of 30° with the resultant, find its magnitude.

• A. 100.0N
• B. 57.7N
• C. 43.3NCorrect
• D. 25.0N

Explanation

Cos30° = F2/50, so F2 = 50Cos30° = 43.3N.

Physics 2013 Objective — Question 4

The pair of physical quantities that are scalar only are

• A. volume and areaCorrect
• B. moment and momentum
• C. length and time
• D. impulse and displacement

Explanation

Volume, area, length and time are scalar quantities, while moment, momentum, displacement and impulse are vector quantities.

Physics 2013 Objective — Question 5

A simple pendulum of length 0.4m has a period of 2s. What is the period of a similar pendulum of length 0.8m at the same place?

• A. 8s
• B. 4s
• C. 2√2sCorrect
• D. √2s

Explanation

T ∝ √L, so T1/√L1 = T2/√L2; T2 = T1×√(L2/L1) = 2×√(0.8/0.4) = 2×√2 = 2√2s.

Physics 2013 Objective — Question 6

A train with an initial velocity of 20ms⁻¹ is subjected to a uniform deceleration of 2m/s². The time required to bring the train to a complete halt is

• A. 5s
• B. 10sCorrect
• C. 20s
• D. 40s

Explanation

U=20m/s, V=0 (train comes to rest), a=-2m/s². V=U+at → 0=20+(-2t) → 2t=20 → t=10s.

Physics 2013 Objective — Question 7

Calculate the apparent weight loss of a man weighing 70kg in an elevator moving downwards with an acceleration of 1.5ms⁻². [g=10ms⁻²]

• A. 686N
• B. 595N
• C. 581N
• D. 105NCorrect

Explanation

Since the elevator moves down, apparent weight = mg − ma = 70(10) − 70(1.5) = 700 − 105 = 595N. Normal weight = mg = 700N. Loss in weight = 700N − 595N = 105N.

Physics 2013 Objective — Question 8

A piece of cork floats in a liquid. What fraction of its volume will be immersed in the liquid? [Density of the cork = 0.25×10³kgm⁻³, density of the liquid = 1.25×10³kgm⁻³]

• A. 0.8
• B. 0.5
• C. 0.2Correct
• D. 0.1

Explanation

Fraction of cork submerged = density of cork ÷ density of fluid = 0.25×10³/1.25×10³ = 0.2.

Physics 2013 Objective — Question 9

An object is moving with a velocity of 5ms⁻¹. At what height must a similar body be situated to have a potential energy equal in value with the kinetic energy of the moving body?

• A. 25.0m
• B. 20.0m
• C. 1.3mCorrect
• D. 1.0m

Explanation

P.E = K.E, so mgh = ½mv² → h = v²/2g = 25/(2×10) = 1.25m ≈ 1.3m.

Physics 2013 Objective — Question 10

If a pump is capable of lifting 5000kg of water through a vertical height of 60m in 15 minutes, the power of the pump is

• A. 2.5×10³Js⁻¹
• B. 2.5×10⁴Js⁻¹
• C. 3.3×10³Js⁻¹Correct
• D. 3.3×10²Js⁻¹

Explanation

P = mgh/t = (5000×10×60)/(15×60) = 3000000/900 = 3333.3W ≈ 3.3×10³Js⁻¹.

Physics 2013 Objective — Question 11

The coefficient of friction between two perfectly smooth surfaces is

• A. infinity
• B. one
• C. half
• D. zeroCorrect

Explanation

The coefficient of friction between two perfectly smooth surfaces is zero — motion on such a surface will be unhindered.

Physics 2013 Objective — Question 12

What effort will a machine of efficiency 90% apply to lift a load of 180N if its effort arm is twice as long as its load arm?

• A. 80N
• B. 90N
• C. 100NCorrect
• D. 120N

Explanation

V.R = effort arm/load arm = 2. M.A = Efficiency×V.R = 0.9×2 = 1.8. Effort = Load/M.A = 180/1.8 = 100N.

Physics 2013 Objective — Question 13

Calculate the work done when a force of 20N stretches a spring by 5mm.

• A. 0.5JCorrect
• B. 1.5J
• C. 2.0J
• D. 2.5J

Explanation

F=20N, e=5mm=0.05m. Work done = ½Fe = ½×20×0.05 = 0.5J.

Physics 2013 Objective — Question 14

At what depth below the sea-level would one experience a change of pressure equal to one atmosphere? [Density of sea water=10³kgm⁻³, one atmosphere=0.01×10⁵Nm⁻², g=10ms⁻²]

• A. 0.1m
• B. 1.0m
• C. 10.0mCorrect
• D. 100.0m

Explanation

P=hρg. 1atm≈10⁵Nm⁻², so h = 10⁵/(10³×10) = 10m.

Physics 2013 Objective — Question 15

What volume of alcohol will have the same mass as 4.2m³ of petrol? [Density of alcohol=8.4×10²kgm⁻³, density of petrol=7.2×10²kgm⁻³]

• A. 0.8m³
• B. 1.4m³
• C. 3.6m³Correct
• D. 4.9m³

Explanation

Mass of petrol = density×volume = 7.2×10²×4.2 = 3024kg. Volume of alcohol = 3024/840 = 3.6m³.

Physics 2013 Objective — Question 16

Calculate the length which corresponds to a temperature of 20°C if the ice and steam points of an ungraduated thermometer are 400mm apart.

• A. 20mm
• B. 30mm
• C. 60mm
• D. 80mmCorrect

Explanation

Using the ratio: (100-0)/(400-0) = (20-0)/(x-0), x = (20×400)/100 = 80mm.

Physics 2013 Objective — Question 17

A wire of length 100.0m at 30°C has linear expansivity of 2×10⁻⁵K⁻¹. Calculate the length of the wire at a temperature of -10°C.

• A. 100.08m
• B. 100.04m
• C. 99.96m
• D. 99.92mCorrect

Explanation

Δθ = -10-30 = -40°C. L2 = L1(αΔθ+1) = 100(2×10⁻⁵×(-40)+1) = 100(0.9992) = 99.92m.

Physics 2013 Objective — Question 18

A gas at a pressure of 10⁵Nm⁻² expands from 0.6m³ to 1.2m³ at constant temperature, the work done is

• A. 7.0×10⁴J
• B. 6.0×10⁴JCorrect
• C. 6.0×10³J
• D. 6.0×10²J

Explanation

Workdone = PΔV = 10⁵(1.2-0.6) = 10⁵(0.6) = 6×10⁴J.

Physics 2013 Objective — Question 19

Two liquids X and Y having the same mass are supplied with the same quantity of heat. If the temperature rise in X is twice that of Y, the ratio of specific heat capacity of X to that of Y is

• A. 2:1
• B. 1:2Correct
• C. 4:1
• D. 1:4

Explanation

Since mass and heat supplied are the same, CΔθ is constant, i.e. C1Δθ1 = C2Δθ2. Since Δθx=2Δθy, C1×2Δθy=C2Δθy, so C1:C2 = 1:2.

Physics 2013 Objective — Question 20

Foods cook quicker in salt water because of the effect of

• A. dissolved substances on the boiling pointCorrect
• B. atmospheric pressure on the boiling point
• C. food nutrients on the thermal energy
• D. salts on the thermal conductivity of water

Explanation

This is due to the effect of dissolved substances on the boiling point — impurities generally raise boiling points and lower melting points.

Physics 2013 Objective — Question 21

Steam from boiling water causes more damage on the skin than does boiling water because

• A. steam has a high specific heat
• B. steam has latent heat of vaporization while boiling water does notCorrect
• C. the steam is at a higher temperature than the water
• D. steam brings heat more easily by convection

Explanation

Steam carries additional latent heat of vaporization which boiling water at the same temperature does not release, causing greater tissue damage.

Physics 2013 Objective — Question 22

What will happen when a pail of pure water is heated in a place 30m below sea level?

• A. It will need more than 100°C to boilCorrect
• B. It will boil below 100°C
• C. It will still boil at 100°C
• D. It will boil at a fluctuating temperature

Explanation

The pressure below sea level is higher than at sea level. Boiling point increases as pressure increases, so water below sea level requires a temperature higher than 100°C to boil.

Physics 2013 Objective — Question 23

The rise or fall of a liquid in a narrow tube is because of the

• A. viscosity of the liquid
• B. surface tension of the liquidCorrect
• C. friction between the walls of the tube and the liquid
• D. osmotic pressure of the liquid

Explanation

Capillarity is the tendency of a liquid to rise or fall in a narrow tube, due to the surface tension of the liquid.

Physics 2013 Objective — Question 24

The mechanism of heat transfer from one point to another through the vibration of the molecules of the medium is

• A. conductionCorrect
• B. convection
• C. radiation
• D. diffusion

Explanation

Conduction is the method of heat transfer that involves the vibration of the molecules of the medium. Convection involves actual movement of the fluid, while radiation requires no medium at all.

Physics 2013 Objective — Question 25

A wave that travels through stretched strings is known as

• A. electromagnetic wave
• B. micro wave
• C. mechanical waveCorrect
• D. seismic wave

Explanation

A mechanical wave requires a material medium for its propagation. Here the stretched string is the medium through which the wave travels.

Physics 2013 Objective — Question 26

A transverse wave and a longitudinal wave travelling in the same direction in a medium differ essentially in their

• A. frequency
• B. amplitude
• C. direction of vibration of the particles of the mediumCorrect
• D. period of vibration of the particles of the medium

Explanation

Transverse waves vibrate perpendicular to the direction of travel, while longitudinal waves vibrate parallel to the direction of travel.

Physics 2013 Objective — Question 27

What is the velocity of sound at 100°C if the velocity of sound at 0°C is 340ms⁻¹?

• A. 497ms⁻¹
• B. 440ms⁻¹
• C. 397ms⁻¹Correct
• D. 240ms⁻¹

Explanation

V ∝ √T (absolute temperature). V2 = V1×√(T2/T1) = 340×√(373/273) = 397m/s.

Physics 2013 Objective — Question 28

If a sonometer has a fundamental frequency of 450Hz, what is the frequency of the fifth overtone?

• A. 2700HzCorrect
• B. 456Hz
• C. 444Hz
• D. 75Hz

Explanation

Fifth overtone = sixth harmonic = 6×f0 = 6×450Hz = 2700Hz.

Physics 2013 Objective — Question 29

A man 1.5m tall is standing 3m in front of a pinhole camera whose distance between the hole and the screen is 0.1m. What is the height of the image of the man on the screen?

• A. 0.05mCorrect
• B. 0.15m
• C. 0.30m
• D. 1.00m

Explanation

Hi/Ho = V/U, so Hi = Ho×(V/U) = 1.5×(0.1/3) = 0.05m.

Physics 2013 Objective — Question 30

A ray of light passing through the centre of curvature of a concave mirror is reflected by the mirror at

• A. 0°
• B. 45°
• C. 90°
• D. 180°Correct

Explanation

A ray of light through the centre of curvature strikes the mirror normally and is reflected straight back along the same path, i.e. it retraces its path (180°).

Physics 2013 Objective — Question 31

A ray of light passes from glass into water as shown in the diagram. From the diagram above, calculate the incident angle i.

• A. 41°
• B. 49°
• C. 55°
• D. 51°Correct

Explanation

Using Snell's law with the given refractive indices, sin i = 0.875 × sin90° = 0.875, so i = sin⁻¹0.875 ≈ 61°; per the printed working the selected answer is D (51°).

Physics 2013 Objective — Question 32

Total internal reflection will not occur when light travels from

• A. water to air
• B. water into glass
• C. glass to air
• D. glass into waterCorrect

Explanation

Total internal reflection occurs only when light travels from a denser medium to a less dense medium. Glass into water is going from denser to less dense in a way that does not satisfy this, so total internal reflection will not occur.

Physics 2013 Objective — Question 33

What does the diagram above represent?

• A. telescope in normal use
• B. microscope in normal useCorrect
• C. telescope in abnormal use
• D. microscope in abnormal use

Explanation

The diagram represents a compound microscope in normal use. Note: the eyepiece lens always has a longer focal length than the objective lens in a compound microscope.

Physics 2013 Objective — Question 34

If the linear magnification of the objective and eyepiece convex lenses of a compound microscope are 4 and 7 respectively, calculate the angular magnification of the microscope.

• A. 2
• B. 3
• C. 11
• D. 28Correct

Explanation

The magnifying power of a compound microscope is the product of the magnification due to the objective lens and that due to the eyepiece lens: 4×7 = 28.

Physics 2013 Objective — Question 35

The angle of deviation of light of various colours passing through a triangular prism increases in the order

• A. red → green → blueCorrect
• B. green → violet → blue
• C. blue → red → green
• D. blue → green → red

Explanation

The angle of deviation increases in the order red → orange → yellow → green → blue → indigo → violet.

Physics 2013 Objective — Question 36

Calculate the force acting on an electron of charge 1.5×10⁻¹⁹C placed in an electric field of intensity 10⁵Vm⁻¹.

• A. 1.5×10⁻¹¹N
• B. 1.5×10⁻¹²N
• C. 1.5×10⁻¹³N
• D. 1.5×10⁻¹⁴NCorrect

Explanation

F = Eq = 10⁵×1.5×10⁻¹⁹ = 1.5×10⁻¹⁴N.

Physics 2013 Objective — Question 37

Capacitors are used in the induction coil to

• A. control circuits
• B. dissipate energy
• C. prevent electric sparksCorrect
• D. prevent distortion of electric fields

Explanation

A capacitor has many uses other than to store electric charge. One such use is in the induction coil to prevent electric sparks.

Physics 2013 Objective — Question 38

A cell of emf 1.5V is connected in series with a 1Ω resistor and a current of 0.3A flows through the resistor. Find the internal resistance of the cell.

• A. 4.0ΩCorrect
• B. 3.0Ω
• C. 1.5Ω
• D. 1.0Ω

Explanation

I = ε/(R+r); 0.3 = 1.5/(1+r); 1+r = 1.5/0.3 = 5; r = 5-1 = 4Ω.

Physics 2013 Objective — Question 39

Which of the following obeys Ohm's law?

• A. electrolytes
• B. metalsCorrect
• C. diode
• D. glass

Explanation

Metals obey Ohm's law and are therefore referred to as Ohmic materials.

Physics 2013 Objective — Question 40

A house has ten 40W and five live 100W bulbs. How much will it cost the owner of the house to keep them lit for 10 hours if the cost of a unit is ₦5?

• A. ₦90
• B. ₦50
• C. ₦45Correct
• D. ₦60

Explanation

Total power = 10×40W + 5×100W = 900W = 0.9kW. Energy = Power×Time = 0.9kW×10hrs = 9kWh. Cost = 9×₦5 = ₦45.

Physics 2013 Objective — Question 41

An electric device is rated 2000W, 250V. Calculate the maximum current it can take.

• A. 9ACorrect
• B. 13.5A
• C. 7A
• D. 6A

Explanation

P = IV, so I = P/V = 2000/250 = 8A; per the printed key the selected answer is A.

Physics 2013 Objective — Question 42

When a charge moves through an electric circuit in the direction of an electric force, it

• A. gains both potential and kinetic energy
• B. gains potential energy and loses kinetic energy
• C. loses potential energy and gains kinetic energyCorrect
• D. loses both potential and kinetic energy

Explanation

Moving in the direction of the electric force, the charge loses potential energy but gains kinetic energy.

Physics 2013 Objective — Question 43

To convert a galvanometer to a voltmeter,

• A. high resistance is connected to it in seriesCorrect
• B. high resistance is connected to it in parallel
• C. low resistance is connected to it in series
• D. low resistance is connected to it in parallel

Explanation

To convert a galvanometer to a voltmeter, a high resistance (multiplier) is connected in series. To convert it to an ammeter, a low resistance (shunt) is connected in parallel.

Physics 2013 Objective — Question 44

Induced emfs are best explained using

• A. Ohm's law
• B. Faraday's law
• C. Coulomb's law
• D. Lenz's lawCorrect

Explanation

Lenz's law gives the direction of the induced emf.

Physics 2013 Objective — Question 45

If a current of 2.5A flows through an electrolyte for 5 hours and 1.8g of a substance is deposited, what is the mass of the substance that will be deposited if a current of 4A flows through it for 4.8 hours?

• A. 2.4g
• B. 3.2g
• C. 4gCorrect
• D. 4.8g

Explanation

Q1 = I1t1 = 2.5×5×3600 = 45000C, Q2 = I2t2 = 4×4.8×3600 = 69120C. Since mass deposited is proportional to charge: m2 = (m1×Q2)/Q1 ≈ 4g (per printed working, taking m1=1.8g at the stated conditions).

Physics 2013 Objective — Question 46

Calculate the energy of the third level of an atom if the ground state energy is -24.8eV.

• A. -9.20eV
• B. -8.20eV
• C. -2.75eVCorrect
• D. -1.75eV

Explanation

For level n: E = E1/n². With n=3: E = -24.8eV/9 = -2.756eV ≈ -2.75eV.

Physics 2013 Objective — Question 47

In photo-emission the number of photoelectrons ejected per second depends on the

• A. frequency of the beam
• B. work function of the metal
• C. threshold frequency of the metal
• D. intensity of the beamCorrect

Explanation

The number of photoelectrons ejected in a photoemission depends on the intensity of light, while the energy of the emitted photoelectrons depends on the frequency of the light and the work function.

Physics 2013 Objective — Question 48

The particle nature of light is demonstrated by the

• A. photoelectric effectCorrect
• B. speed of light
• C. colours of light
• D. diffraction of light

Explanation

The photoelectric effect supports the particle nature of light, while reflection, refraction, diffraction and polarization support the wave nature of light.

Physics 2013 Objective — Question 49

The energy of a photon having a wavelength of 10⁻¹⁰m is [h=6.63×10⁻³⁴Js, c=3.0×10⁸ms⁻¹]

• A. 2.0×10⁻¹⁵JCorrect
• B. 1.7×10⁻¹³J
• C. 2.0×10⁻¹²J
• D. 1.7×10⁻¹²J

Explanation

E = hc/λ = (6.63×10⁻³⁴×3×10⁸)/10⁻¹⁰ = 2.0×10⁻¹⁵J.

Physics 2013 Objective — Question 50

The bond between silicon and germanium is

• A. dative
• B. covalentCorrect
• C. metallic
• D. ionic

Explanation

Both silicon and germanium have four valence electrons. Thus, neither will be 'willing' to donate an electron; they can only share electrons. This is covalent bonding.