JAMB Physics 1983 past questions and answers

In a resonance tube experiment, a tube of fixed length is closed at one end and several tuning forks of increasing frequency used to obtain resonance at the open end. If the tuning fork with the lowest frequency which gave resonance had a frequency f₁ and the next tuning fork to give resonance had a frequency f₂, find the ratio f₂/f₁.

1. A.8
2. B.3
3. C.2
4. D.½
5. E.⅓

Which of the following is NOT a vector quantity?

1. A.Force
2. B.Altitude
3. C.Weight
4. D.Displacement
5. E.Acceleration

Consider the three forces acting at O and in equilibrium as shown in Fig. 1. Which of the following equations is/are CORRECT? I. P₁ cos θ₁ = P₂ cos θ₂ II. P₃ = P₁ cos θ₁ + P₂ cos θ₂ III. P₁ sin θ₁ = P₂ sin θ₂

1. A.I only
2. B.II only
3. C.III only
4. D.II and III only
5. E.I and III only.

Which of the following statements about friction is NOT correct?

1. A.The force of kinetic friction is less than the force of static friction
2. B.The force of kinetic friction between two surfaces is independent of the areas in contact provided the normal reaction is unchanged.
3. C.The force of rolling friction between two surfaces is less than the force of sliding friction
4. D.The angle of friction is the angle between the normal reaction and the force of friction.
5. E.Friction may be reduced by lubrication.

A brick at rest on a horizontal table is pulled by a horizontal cord, as shown in Fig. 2. The force of friction on the brick

1. A.increases if the pull increases but the brick does not move
2. B.is directly horizontal to the right
3. C.decreases if an identical brick is placed on the first
4. D.is zero if the brick is pulled hard enough to make it slide
5. E.change if the brick is turned on its side.

The force with which an object is attracted to the earth is called its

1. A.acceleration
2. B.mass
3. C.gravity
4. D.impulse
5. E.weight

The refractive index of a liquid is 1.5. If the velocity of light in vacuum is 3.0 × 10⁸ m s⁻¹, the velocity of light in the liquid is

1. A.1.5 × 10⁸ m s⁻¹
2. B.2.0 × 10⁸ m s⁻¹
3. C.3.0 × 10⁸ m s⁻¹
4. D.4.5 × 10⁸ m s⁻¹
5. E.9.0 × 10⁸ m s⁻¹

If the relative density of a metal is 19, what will be the mass of 20 cm³ of the metal when immersed in water?

1. A.380 g
2. B.400 g
3. C.360 g
4. D.39 g
5. E.180 g

Which of the following statements about liquid pressure is NOT correct? The pressure

1. A.at a point in a liquid is proportional to the depth
2. B.at any point in a liquid is the same at the same level
3. C.is exerted equally in all directions at any point
4. D.of a liquid at any point on the wall of its container acts in a direction perpendicular to the wall.
5. E.at a particular depth depends on the shape of the vessel.

A ship travelling towards a cliff receives the echo of its whistle after 3.5 seconds. A short while later, it receives the echo after 2.5 seconds. If the speed of sound in air under the prevailing conditions is 250 m s⁻¹, how much closer is the ship to the cliff?

1. A.10 m
2. B.125 m
3. C.175 m
4. D.350 m
5. E.1,000 m.

Which of the following is NOT correct? I. The pitch of a sound note depends on the frequency of vibrations. II. The intensity of a sound note is proportional to the amplitude of vibrations. III. Beats are produced by two sources of sound because one wave is travelling faster than the other. IV. When two sources of sound of frequencies 500 Hz and 502 Hz are sounded together, a beat frequency of 2 Hz is observed. V. The first harmonic of a note has double the frequency of the fundamental note.

1. A.I and II
2. B.II and III
3. C.I and III
4. D.III and IV
5. E.IV and V.

Which of the following statements about defects of vision is/are CORRECT? I. For a long sighted person, close objects appear blurred. II. For a short sighted person, distant objects appear blurred III. Short sight is corrected by using a pair of converging lenses.

1. A.I only
2. B.II only
3. C.I and II only
4. D.II and III only
5. E.I, II and III.

The range of wavelengths of the visible spectrum is 400 nm − 700 nm. The wavelength of gamma rays is

1. A.longer than 700 nm
2. B.shorter than 700 nm but longer than 400 nm
3. C.550 nm
4. D.shorter than 400 nm
5. E.infinite.

If the pressure on 100 cm³ of an ideal gas is doubled while its Kelvin temperature is halved, then the new volume of the gas will become

1. A.25 cm³
2. B.50 cm³
3. C.100 cm³
4. D.200 cm³
5. E.400 cm³.

A train has an initial velocity of 44 m/s and an acceleration of −4 m/s². Its velocity after 10 seconds is

1. A.2 m/s
2. B.4 m/s
3. C.8 m/s
4. D.12 m/s
5. E.16 m/s

Which of the following conditions are necessary and sufficient for total internal reflection to take place at the boundary between two optical media? I. Light is passing from optically denser medium to optically less dense medium II. Light is passing from optically less dense medium to optically denser medium III. Angle of incidence is greater IV. Angle of incidence is lesser

1. A.I and II only
2. B.II and III only
3. C.III and IV only
4. D.I and III only
5. E.II and IV only.

A man of mass 50 kg ascends a flight of stairs 5 m high in 5 seconds. If acceleration due to gravity is 10 m s⁻², the power expended is

1. A.100 W
2. B.200 W
3. C.250 W
4. D.400 W
5. E.500 W

Which of the following arrangements in the sequence shown can be used to obtain a pure spectrum of white light?

1. A.Source, slit, converging lens, prism, converging lens, screen
2. B.Source, slit, diverging lens, prism, diverging lens, screen
3. C.Source, converging lens, prism, diverging lens, screen
4. D.Source, slit, diverging lens, converging lens, screen
5. E.Source, slit, prism, diverging lens, screen.

The diagrams in Fig. 3 show three circuits. The internal resistances of the batteries are negligible. Which of the currents is the largest?

1. A.I₁
2. B.I₂
3. C.I₃
4. D.I₄
5. E.I₅.

A milliameter with full scale deflection of 10 mA has an internal resistance of 5 ohms. It would be converted to an ammeter with a full scale deflection of 1 A by connecting a resistance of

1. A.5/99 ohm in series with it
2. B.5/99 ohm in parallel with it
3. C.99/5 ohm in parallel with it
4. D.99/5 ohm in series with it
5. E.2 ohms in series with it.

It is usual to transmit electric power at high voltage and low current. Which of the following are possible advantages of the method? I. Heat losses are reduced because the currents are small II. Thin wires can be used because small currents are flowing III. The power can flow faster because the voltage is high

1. A.I only
2. B.I and II only
3. C.II and III only
4. D.I and III only
5. E.I, II and III.

The linear expansivity of brass is 2 × 10⁻⁵ °C⁻¹. If the volume of a piece of brass is 10 cm³ at 0°C, what will be its volume at 100°C?

1. A.10.02 cm³
2. B.10.04 cm³
3. C.10.06 cm³
4. D.10.20 cm³
5. E.102.00 cm³.

A 24 V potential difference is applied across a parallel combination of four 6-ohm resistors. The current in each resistor is

1. A.1 A
2. B.4 A
3. C.16 A
4. D.18 A
5. E.36 A

In the circuit shown in Fig. 4, T is a resistor whose resistance falls as temperature increases. L₁ and L₂ are lamps. Assuming the cell has negligible internal resistance, as the temperature of T increases.

1. A.L₁ becomes brighter, L₂ becomes dimmer
2. B.L₁ and L₂ becomes brighter
3. C.L₁ becomes dimmer, L₂ becomes brighter
4. D.L₁ becomes brighter, L₂ does not change
5. E.L₂ becomes dimmer, L₁ does not change.

Which of the diagrams in Fig. 5 gives the correct resultant R of two vectors P and Q?

1. A.I
2. B.II
3. C.III
4. D.IV
5. E.V

The electrochemical equivalent of a metal is 0.126 × 10⁻⁶ kg/C. The mass of the metal that a current of 5 A will deposit from a suitable bath in 1 hour is

1. A.0.0378 × 10⁻³ kg
2. B.0.227 × 10⁻³ kg
3. C.0.378 × 10⁻³ kg
4. D.0.595 × 10⁻³ kg
5. E.2.268 × 10⁻³ kg.

Ripples on water are similar to light waves in that they both

1. A.have the same wavelength
2. B.are longitudinal
3. C.cannot be reflected
4. D.travel at the same speed
5. E.can be refracted and diffracted.

A piece of wood is floating on water. The forces acting on the wood are

1. A.upthrust and reaction
2. B.weight and reaction
3. C.weight and upthrust
4. D.upthrust and viscosity
5. E.weight and viscosity.

A force of 16 N applied to a 4.0 kg block that is at rest on a smooth, horizontal surface. What is the velocity of the block at t = 5 seconds?

1. A.4 m/s
2. B.10 m/s
3. C.20 m/s
4. D.50 m/s
5. E.80 m/s.

1,000 identical drops of oil of density 500 kg/m³ have a total mass of 5 × 10⁻⁴ kg. One of the drops forms a thin film of area 0.5 m² on water. The thickness of the film is

1. A.2 × 10⁻⁸ m
2. B.2 × 10⁻⁹ m
3. C.2 × 10⁻⁷ m
4. D.3 × 10⁻⁹ m
5. E.2.8 × 10⁻⁸ m.

The total length of a spring when a mass of 20 g is hung from its end is 14 cm, while its total length is 16 cm when a mass of 30 g is hung from the same end. Calculate the unstretched length of the spring assuming Hooke's law is obeyed.

1. A.9.33 cm
2. B.10.00 cm
3. C.10.66 cm
4. D.12.00 cm
5. E.15.00 cm

Each of the diagrams in Fig. 6 represents two current carrying conductors situated close to each other. In which two diagrams are the forces between the two wires attractive?

1. A.I and V
2. B.I and III
3. C.II and IV
4. D.II and V
5. E.III and IV.

Which of the following statements is CORRECT? I. The mass number is equal to the total number of protons and electrons in an atom II. The atomic number is equal to the number of protons in an atom III. The number of electrons in an atom is equal to the total number of protons and neutrons in the nucleus.

1. A.I only
2. B.II only
3. C.III only
4. D.I and II only
5. E.II and III only.

A short response time is obtained in liquid-in-glass thermometer when the

1. A.bulb is large and thick-walled
2. B.stem is long and thin
3. C.bulb is small and thick-walled
4. D.liquid is of high density and the bore is large
5. E.bulb is thin-walled and the liquid is a good conductor of heat.

A machine has a velocity ratio of 5. It requires a 50 kg weight to overcome a 200 kg weight. The efficiency is

1. A.4%
2. B.5%
3. C.40%
4. D.50%
5. E.80%

If the normal atmospheric pressure in a laboratory supports a column of mercury 0.76 m high and the relative density of mercury is 13.8, then the height of water column which atmospheric pressure will support in the same laboratory at the same time is

1. A.0 m
2. B.10 m
3. C.13 m
4. D.14 m
5. E.18 m.

An electric current of 3 A flowing through an electric heating element of resistance 20 Ω embedded in 1,000 g of an oil raises the temperature of the oil by 10°C in 10 seconds, then the specific heat capacity of the oil is

1. A.1.8 J/g
2. B.0.6 J/g
3. C.0.18 J/g°C
4. D.1.8 J/g°C
5. E.0.06 J/g°C

The difference of potential between the terminals of a cell is 2.2 volts. When a 4 ohm resistor is connected across the terminals of this cell, the potential difference is 2 volts. What is the internal resistance of the cell?

1. A.0.10 ohms
2. B.0.25 ohms
3. C.0.40 ohms
4. D.2.50 ohms
5. E.4.00 ohms

In Fig. 7 above, QR is a vertical conductor and the current I flows from R to Q. P is a point on the horizontal plane and is to the South of the wire. The direction of the magnetic field at P due to the current is

1. A.upward
2. B.north
3. C.south
4. D.west
5. E.east

Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?

1. A.Heat → Light → Sound → Kinetic
2. B.Kinetic → Light → Heat → Electricity
3. C.Heat → Kinetic → Electricity → Heat and Light
4. D.Electricity → Kinetic → Heat → Light
5. E.Heat → Sound → Kinetic → Electricity

Which of the following statements clearly describe the behaviour of the fire alarm shown in Fig. 8 below given that the linear expansivities of copper and steel are 2.0 × 10⁻⁵/°C and 1.2 × 10⁻⁵/°C respectively? I. The bimetallic strip will not be able to close the circuit when there is fire II. The bimetallic strip will close the circuit when there is fire III. If the copper and steel are interchanged, the circuit will close when there is fire.

1. A.I only
2. B.II only
3. C.III only
4. D.I and III
5. E.II and III.

Four equal resistors R₁, R₂, R₃ and R₄ are connected in series as shown in Fig. 9 below. V₁, V₂ and V₃ are voltmeters connected as indicated. Which of the following relations is CORRECT?

1. A.V₁ = V₃ = V₂/2
2. B.V₁ = 2V₂ = V₃
3. C.V₁ = ½V₃ = V₂
4. D.V₁ − V₃ = V₂
5. E.V₂ − V₁ = V₃/2

Which of the following may be used to determine the relative humidity in a physics laboratory? I. Manometer II. Wet-and-dry bulb hygrometer III. Hair hygrometer IV. A hydrometer.

1. A.I only
2. B.II and III only
3. C.II only
4. D.III only
5. E.II, III and IV only

PQ is a thin rod on a horizontal table, RS is a plane mirror inclined at 45° to the horizontal as shown in Fig. 10 above. The image of PQ as seen in the mirror by the eye, T is

1. A.horizontal
2. B.parallel to the mirror
3. C.at infinity
4. D.vertical
5. E.highly magnified

The speed of light in vacuum is 3.0 × 10⁸ m s⁻¹. If the refractive index of a transparent liquid is 4/3, then the speed of light in the liquid is

1. A.0.44 × 10⁸ m s⁻¹
2. B.2.25 × 10⁸ m s⁻¹
3. C.3.0 × 10⁸ m s⁻¹
4. D.4.0 × 10⁸ m s⁻¹
5. E.4.33 × 10⁸ m s⁻¹

If the force on a charge of 0.2 coulomb in an electric field is 4 N, then the electric field intensity of the field is

1. A.0.8
2. B.0.8 N/C
3. C.20.0 N/C
4. D.4.2 N/C
5. E.20.0 C/N

The specific latent heat of vaporization of a substance is always

1. A.less than its specific latent heat of fusion
2. B.greater than its specific latent heat of fusion
3. C.equal to its specific latent heat of fusion
4. D.all of the above depending on the nature of the substance
5. E.none of the above.

Longitudinal waves do not exhibit

1. A.refraction
2. B.reflection
3. C.diffraction
4. D.polarization
5. E.rarefaction

Fig. 11 above shows an inverted U-tube with the open end, O of one limb below the level, W, of water in a tank. In order that water should begin to flow from the tank it is necessary that

1. A.the U-tube is completely filled with water and P should be higher than W.
2. B.P should be lower than O and W
3. C.P should be lower than W and O should reach to the bottom of the vessel
4. D.The U-tube is completely filled with water and P should be lower than W
5. E.the U-tube is completely filled with water and O should reach the bottom of the vessel.