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Free JAMB Past Question for physics

Q.1

A body is undergoing Simple Harmonic Motion (S.H.M.). At which point is its acceleration at a maximum?

A. At the midpoint (equilibrium position).

B. At the extreme positions.

C. When the velocity is at a maximum.

D. When the displacement is at a minimum.


Correct Answer: option b

Further reading: Motion - Velocity and acceleration of S.H.M

Show explanation

In Simple Harmonic Motion, the acceleration of the oscillating body is directly proportional to its displacement from the equilibrium position and is always directed towards that position. Therefore, the acceleration is at its maximum at the extreme positions of the oscillation, where the displacement is at its maximum

Q.2

A parallel circuit consists of three resistors with values of 2 Ω, 3 Ω, and 6 Ω. What is the total effective resistance of the circuit?

A. 11 Ω

B. 6 Ω

C. 1 Ω

D. 0.5 Ω


Correct Answer: option c

Further reading: Current Electricity - Resistance in series and in parallel and their combination

Show explanation

For resistors connected in parallel, the reciprocal of the total effective resistance ($R_T$) is the sum of the reciprocals of the individual resistances. The formula is 1/RT=1/R1+1/R2+1/R31/R_T = 1/R_1 + 1/R_2 + 1/R_3 . Substituting the given values, we get 1/RT=1/2+1/3+1/61/R_T = 1/2 + 1/3 + 1/6 . Finding a common denominator, we get 1/RT=3/6+2/6+1/6=6/6=11/R_T = 3/6 + 2/6 + 1/6 = 6/6 = 1 . Therefore, RT=1R_T = 1 Ω.

Q.3

Which of the following is a condition for the resonance of a series R-L-C circuit?

A. The inductive reactance is equal to the resistance.

B. The capacitive reactance is equal to the resistance.

C. The impedance is at its maximum value.

D. The inductive reactance is equal to the capacitive reactance.


Correct Answer: option d

Further reading: Simple A.C. Circuits - Resonance and resonance frequency

Show explanation

Resonance in a series R-L-C circuit occurs when the inductive reactance (XLX_L ) is equal to the capacitive reactance (XCX_C ). At this frequency, the circuit's impedance is at its minimum and is equal to the resistance (R), and the current is at its maximum.

Q.4

Which of the following is a vector quantity?

A. Speed

B. Mass

C. Work

D. Momentum


Correct Answer: option d

Further reading: Scalars and Vectors - Definition of scalar and vector quantities

Show explanation

A vector quantity is a physical quantity that has both magnitude and direction. Momentum is a vector quantity, as it is the product of mass (a scalar) and velocity (a vector), and it has a direction. Speed, mass, and work are all scalar quantities, having only magnitude.

Q.5

Which of the following is a direct application of the principle of conservation of linear momentum?

A. A rocket propelled into space.

B. A car moving on a straight road.

C. A ball bouncing off a wall.

D. A satellite orbiting the Earth.


Correct Answer: option a

Further reading: Motion - Conservation of linear momentum

Show explanation

The principle of conservation of linear momentum states that in the absence of external forces, the total momentum of a system remains constant. A rocket uses this principle by expelling hot gases at high velocity in one direction. To conserve the total momentum of the rocket-gas system, the rocket itself gains momentum in the opposite direction, propelling it forward.

Q.6

A car moving at a velocity of 20 m/s accelerates uniformly at 2 m/s² for 5 seconds. What is the final velocity of the car?

A. 25 m/s

B. 30 m/s

C. 40 m/s

D. 20 m/s


Correct Answer: option b

Further reading: Motion - Equations of uniformly accelerated motion

Show explanation

The first equation of motion for uniformly accelerated motion is v=u+atv = u + at , where vv is the final velocity, uu is the initial velocity, aa is the acceleration, and tt is the time. We are given u=20u = 20m/s, a=2a = 2 m/s², and t=5t = 5s. Substituting the values, we get v=20+(2)(5)=20+10=30v = 20 + (2)(5) = 20 + 10 = 30m/s.

Q.7

A boy is pulling a block with a force of 40 N at an angle of 60° to the horizontal. What is the horizontal component of the force?

A. 20 N

B. 34.64 N

C. 40 N

D. 23.09 N


Correct Answer: option a

Further reading: Scalars and Vectors - Resolution of vectors into two perpendicular directions

Show explanation

The horizontal component of a force (FxF_x ) is found by multiplying the magnitude of the force (FF ) by the cosine of the angle (θ\theta ) it makes with the horizontal. The formula is Fx=Fcos(θ)F_x = F \cos(\theta). Substituting the values, Fx=40cos(60)=40×0.5=20F_x = 40 \cos(60^\circ) = 40 \times 0.5 = 20 N.

Q.8

A person holds a stone and drops it from a height. Which of the following describes the energy transformation as the stone falls?

A. Kinetic energy is converted into potential energy.

B. Potential energy is converted into kinetic energy.

C. Chemical energy is converted into kinetic energy.

D. Heat energy is converted into kinetic energy.


Correct Answer: option b

Further reading: Work, Energy and Power - Qualitative treatment between different forms of energy

Show explanation

When the stone is held at a certain height, it possesses gravitational potential energy. As it is dropped, this potential energy is converted into kinetic energy, the energy of motion. The potential energy is at its maximum at the beginning of the fall and becomes zero at the ground, while the kinetic energy is zero at the beginning and becomes maximum just before it hits the ground

Q.9

In a parallel-plate capacitor, if the potential difference across the plates is doubled while keeping the plate separation constant, what happens to the energy stored in the capacitor?

A. It is halved.

B. It is doubled.

C. It remains the same.

D. It is quadrupled.


Correct Answer: option d

Further reading: Capacitors - Energy stored in a capacitor

Show explanation

The energy stored in a capacitor (E) is given by the formula E=12CV2E = \frac{1}{2}CV^2 , where $ is the capacitance and $V$ is the potential difference. The capacitance of a parallel plate capacitor is given by C=ϵAdC = \frac{\epsilon A}{d} , which is constant if the area (A) and separation ($d$) are constant. If the potential difference (V) is doubled, the new potential difference is 2V. The new energy stored will be Enew=12C(2V)2=12C(4V2)=4(12CV2)=4EE_{new} = \frac{1}{2}C(2V)^2 = \frac{1}{2}C(4V^2) = 4(\frac{1}{2}CV^2) = 4E . Therefore, the energy stored is quadrupled.

Q.10

What is the main reason for the transmission of power at high voltage and low current?

A. To increase the speed of the electricity.

B. To reduce the loss of energy due to heating.

C. To make the electricity safer for the consumer.

D. To increase the power delivered.


Correct Answer: option b

Further reading: Electrical Energy and Power - Electric power transmission

Show explanation

Electrical power is transmitted over long distances using high-voltage transmission lines. The power loss in a transmission line is given by Ploss=I2RP_{loss} = I^2R , where II is the current and R is the resistance of the cable. The power being transmitted is P=VIP = VI , where V is the voltage. For a constant power, if the voltage (V) is increased, the current (I) must be decreased. By decreasing the current, the power loss due to the heating effect of the current (I2RI^2R ) is significantly reduced, making the transmission more efficient

Q.11

What is the primary method of heat transfer from the Sun to the Earth?

A. Conduction

B. Convection

C. Radiation

D. Absorption


Correct Answer: option c

Further reading: Heat Transfer - Conduction, convection and radiation as modes of heat transfer

Show explanation

Radiation is the transfer of heat through electromagnetic waves, and it does not require a material medium. The space between the Sun and the Earth is a vacuum, so heat can only be transferred by radiation. Conduction and convection require a medium for transfer

Q.12

What is the function of a fuse in a domestic electrical circuit?

A. To increase the voltage in the circuit.

B. To store electrical energy.

C. To protect the circuit from excessive current.

D. To regulate the current flow.


Correct Answer: option c

Further reading: Electrical Energy and Power - Use of fuses

Show explanation

A fuse is a safety device used in an electrical circuit to protect it from excessive current (overcurrent). It contains a wire designed to melt and break the circuit if the current flowing through it exceeds a certain rating, thus preventing damage to appliances or the risk of fire

Q.13

What is the function of a galvanometer in an electrical circuit?

A. To measure the potential difference.

B. To measure the electric current.

C. To detect and measure small currents.

D. To regulate the voltage.


Correct Answer: option c

Further reading: Force on a Current-Carrying Conductor in a Magnetic Field - Moving coil and moving iron instruments

Show explanation

A galvanometer is a type of ammeter used to detect and measure very small electric currents. It is the core component of many analog measuring instruments, and it can be converted into an ammeter or a voltmeter by adding a shunt or a multiplier resistance, respectively

Q.14

The velocity v of a particle in a time t is given by the equation v=10+2t2v=10+2t^2 . Find the instantaneous acceleration after 5 seconds.


A. 10ms110ms^{-1}

B. 15ms115ms^{-1}

C. 20ms120ms^{-1}

D. 60ms160ms^{-1}



Correct Answer: option c

Show explanation

1. Identify the velocity equation: v=10+2t2

2. Recall relationship between velocity and acceleration: Acceleration (a) is the first derivative of velocity with respect to time ( a=dvdta=\frac{dv}{dt} )

3. Differentiate the velocity equation:

  1. a=ddt(10+2t2)a=\frac{d}{dt}(10+2t^2)
  2. a=0+2×2t
  3. a=4t

4. Substitute the given time (t=5 s):

  1. a=4×5=20ms1a=4×5=20 ms^{-1}
  2. a=20ms1\therefore a=20ms^{-1}


Q.15

A radioactive element has a half-life of 10 years. What fraction of the original sample will be remaining after 30 years?

A. 1/2

B. 1/4

C. 1/8

D. 1/16


Correct Answer: option c

Further reading: Elementary Modern Physics - Half-life and decay constant

Show explanation

The half-life is the time it takes for half of the radioactive atoms in a sample to decay. In 30 years, there will have been 3 half-lives (30 years / 10 years/half-life = 3 half-lives). After the first half-life, 1/2 of the sample remains. After the second, 1/2 of that remains, which is 1/4 of the original. After the third half-life, 1/2 of the 1/4 remains, which is 1/8 of the original sample

Q.16

In the context of the atomic structure, which of the following is true about isotopes of an element?

A. They have the same number of neutrons but different numbers of protons.

B. They have the same number of electrons but different numbers of protons.

C. They have the same number of protons but different numbers of neutrons.

D. They have different numbers of protons, neutrons, and electrons.

Correct Answer: option c

Further reading: Elementary Modern Physics - Isotopes of an element

Show explanation

Isotopes of an element are atoms that have the same number of protons (atomic number) but a different number of neutrons. Because they have the same number of protons, they belong to the same chemical element. The difference in the number of neutrons results in different mass numbers. For example, Carbon-12 and Carbon-14 are isotopes of carbon, both having 6 protons, but Carbon-12 has 6 neutrons while Carbon-14 has 8 neutrons.

Q.17

What is the function of a commutator in a DC motor?

A. To convert AC to DC.

B. To reverse the direction of current in the coil every half rotation.

C. To increase the strength of the magnetic field.

D. To provide a continuous supply of current to the coil.


Correct Answer: option b

Further reading: Force on a Current-Carrying Conductor in a Magnetic Field - The d. c. motor

Show explanation

A DC motor works by a force exerted on a current-carrying coil in a magnetic field. To ensure the motor continues to rotate in one direction, the direction of the current in the coil must be reversed every half rotation. The commutator is a device that performs this function, reversing the current and ensuring that the torque always acts in the same direction, leading to continuous rotation.

Q.18

What is the primary characteristic that distinguishes a transverse wave from a longitudinal wave?

A. The speed of the wave.

B. The direction of particle vibration relative to the wave propagation.

C. The medium through which the wave travels.

D. The frequency of the wave.


Correct Answer: option b

Further reading: Waves - Longitudinal and transverse waves

Show explanation

The key difference between a transverse wave and a longitudinal wave is the direction of vibration of the particles of the medium relative to the direction of wave propagation. In a transverse wave, the particles of the medium vibrate perpendicularly to the direction of wave propagation (e.g., light waves). In a longitudinal wave, the particles of the medium vibrate parallel to the direction of wave propagation (e.g., sound waves).

Q.19

What is the phenomenon responsible for the bending of a bimetallic strip when heated?

A. Anomalous expansion of water.

B. Linear expansivity.

C. Volume expansivity.

D. High heat capacity.


Correct Answer: option b

Further reading: Thermal Expansion - Effects and applications

Show explanation

A bimetallic strip is made of two metals with different coefficients of linear expansion. When heated, the metal with the higher linear expansivity expands more than the other. This unequal expansion causes the strip to bend, with the more expansive metal on the outside of the curve. This principle is used in thermostats and thermometers

Q.20

A traveling wave moving from left to right has an amplitude of 0.15m, a frequency of 550 Hz and a wavelength of 0.01m. The equation describing the wave is


A.9 y=0.15sin200π(x−5.5t)

B. y=0.15sinπ(0.01x−5.5t)

C. y=0.15sin5.5π(x−200t)

D. y=0.15sinπ(550x−0.01t)

Correct Answer: option a

Show explanation

1. General wave equation: For a wave moving in the positive x-direction is y=Asin(kx−ωt), where A is amplitude, k is wave number, and ω is angular frequency.


2. Extract given values:

  1. Amplitude (A) = 0.15 m
  2. Frequency (f) = 550 Hz
  3. Wavelength (λ) = 0.01 m


  1. Calculate wave speed (v):
  2. v=fλ=550 Hz×0.01 m=5.5 m/s

3. Calculate angular frequency (ω):

  1. ω=2πf=2π×550=1100π rad/s


4. Calculate wave number (k):

  1. k=2πλ=2π0.01=200πrad/m\frac{2π}{λ}=\frac{2π}{0.01}=200π rad/m


5. Substitute values into the general equation:

  1. y=0.15sin(200πx−1100πt)


6. Factor out 200π to match option A's format (y=Asin[k(x−vt)], where k=200π and v=5.5):

  1. y=0.15sin[200π(x−(1100π/200π)t)]
  2. y=0.15sin[200π(x−5.5t)]


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