Electrostatics

Electrostatics MDCAT MCQs with answers

113 past paper MCQs from Physics unit 8, Electrostatics, across 7 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

Practise as a quiz

Coulomb’s Law

1.If we double the separation between two charges, then Coulomb's force will become: (MDCAT 2020)

  1. doubled
  2. half
  3. four times
  4. one fourth
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Correct answer: (d) one fourth

$F\propto1/r^2$, so twice the separation leaves a quarter of the force.

2.Which one of the following statements is true? (MDCAT 2022)

  1. the electrostatic force obeys the inverse square law while the gravitational force does not
  2. both the gravitational force and the electrostatic force are repulsive in nature
  3. the gravitational force is much weaker than the electrostatic force
  4. neither force obeys the inverse square law
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Correct answer: (c) the gravitational force is much weaker than the electrostatic force

Both are inverse square forces, but between two protons gravity is weaker by some $10^{36}$ times.

3.The Coulomb constant depends upon the: (MDCAT 2022)

  1. nature of the medium
  2. system of units
  3. type of charge
  4. nature of the medium and the system of units
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Correct answer: (d) nature of the medium and the system of units

$k=1/4\pi\varepsilon$ carries the permittivity of the medium, and its number depends on the units used.

All 23 Coulomb’s Law MCQs → Coulomb’s Law notes →

Electric Field and Field Intensity

4.A charged particle is moving in a uniform electric field. For the motion of the particle due to the field, which quantity has a constant non-zero value? (MDCAT 2022)

  1. acceleration
  2. displacement
  3. rate of change of acceleration
  4. velocity
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Correct answer: (a) acceleration

A uniform field gives a constant force, so the acceleration $qE/m$ is constant.

5.The electric field intensity inside a charged hollow sphere is: (MDCAT 2023)

  1. maximum
  2. zero
  3. negative
  4. positive
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Correct answer: (b) zero

The charge resides on the outer surface and its contributions cancel everywhere inside, so the field there is zero.

6.Which one of the following is NOT a feature of electric forces? (MDCAT 2024)

  1. they act on charges
  2. they act on masses
  3. they can be attractive
  4. they can be repulsive
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Correct answer: (b) they act on masses

Electric forces act on charge; it is the gravitational force that acts on mass.

All 19 Electric Field and Field Intensity MCQs → Electric Field and Field Intensity notes →

Representation of the Electric Field by Lines

7.A negatively charged particle initially at rest is placed in an electric field which varies from point to point, with no other field present. Then: (UHS MDCAT 2017)

  1. the particle moves along the electric line of force passing through it
  2. the particle moves opposite to the electric line of force passing through it
  3. the direction of acceleration of the particle is tangential to the electric line of force at every instant
  4. the direction of acceleration of the particle is normal to the electric line of force at every instant
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Correct answer: (c) the direction of acceleration of the particle is tangential to the electric line of force at every instant

The force is always along the field, so the acceleration is tangential to the line of force, but a curved line of force is not the path the particle takes.

8.Electric field lines due to a positive charge are: (PMC Practice 2021)

  1. Always horizontal
  2. Always vertical
  3. Radially towards the charge
  4. Radially away from the charge
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Correct answer: (d) Radially away from the charge

Lines leave a positive charge and run straight outwards in every direction.

9.A negatively charged particle initially at rest is placed in an electric field that varies from point to point. There are no other fields. Then: (UHS MDCAT 2017)

  1. The particle moves along the electric line of force passing through it.
  2. The particle moves opposite to the electric line of force passing through it.
  3. The direction of acceleration of the particle is tangential to the electric line of force at every instant.
  4. The direction of acceleration of the particle is normal to the electric line of force at every instant.
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Correct answer: (c) The direction of acceleration of the particle is tangential to the electric line of force at every instant.

The force, and so the acceleration, is along the field line at each point, that is along the tangent of the curved line.

Representation of the Electric Field by Lines notes →

Electric Field Due to an Infinite Sheet of Charge

10.The electric intensity between two oppositely charged plates in the middle region is: (MDCAT 2024)

  1. non-uniform
  2. uniform
  3. unpredictable
  4. variable
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Correct answer: (b) uniform

Away from the edges the field between two parallel charged plates is uniform, $E=\sigma/\varepsilon_0$.

11.If the surface charge density of an infinite sheet increases by 25%, the electric field intensity: (UHS MDCAT 2025)

  1. Increases by 25%
  2. Increases by 50%
  3. Decreases by 25%
  4. Remains the same
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Correct answer: (a) Increases by 25%

The field of an infinite sheet is proportional to the surface charge density, so it rises in the same proportion.

12.Electric field intensity of infinite charge sheet: (NUMS MDCAT 2025)

  1. E = 2σ/ε0
  2. E = 1/ε0
  3. E = σ/ε0
  4. σ/(2ε0)
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Correct answer: (d) σ/(2ε0)

The field of an infinite sheet is $\sigma/2\varepsilon_0$ and does not fall off with distance.

All 15 Electric Field Due to an Infinite Sheet of Charge MCQs → Electric Field Due to an Infinite Sheet of Charge notes →

Electric Potential and Potential Energy

13.The formula $V=W/q$ represents: (MDCAT 2024)

  1. electric intensity
  2. electric power
  3. electric potential
  4. electric field gradient
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Correct answer: (c) electric potential

Potential is the work done per unit positive charge in bringing it from infinity to that point.

14.Find the potential difference in moving a 2 C charge which requires 600 J of work between two points. (MDCAT 2024)

  1. 1200 V
  2. 300 V
  3. 150 V
  4. 2400 V
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Correct answer: (b) 300 V

$V=W/q=600/2=300$ V.

15.How much power is used in moving a charge of \$0.03\,\mathrm{C}\$ from a point at \$40\,\mathrm{V}\$ to a point at \$60\,\mathrm{V}\$ in \$2\,\mathrm{s}\$? (UHS MDCAT 2017)

  1. $0.30\,\mathrm{W}$
  2. $0.15\,\mathrm{W}$
  3. $0.60\,\mathrm{W}$
  4. $0.012\,\mathrm{W}$
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Correct answer: (a) $0.30\,\mathrm{W}$

$W=q\Delta V=0.03\times20=0.6\,\mathrm{J}$, so $P=0.6/2=0.30\,\mathrm{W}$.

All 19 Electric Potential and Potential Energy MCQs → Electric Potential and Potential Energy notes →

Electric Potential Due to a Point Charge

16.The electric potential at a distance r is given by the formula: (NUMS MDCAT 2025)

  1. V = kq/r
  2. 1/4πε0qr
  3. Ed
  4. Ir
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Correct answer: (a) V = kq/r

The potential of a point charge at a distance $r$ is $kq/r$.

17.Two points charges, +5µC and -5µC are placed at points A and B, respectively, which are separated by a distance 2d. What is the electric potential at the midpoint M of the line joining A and B? (KMU MDCAT 2024)

  1. 2kQ/d
  2. kQ/d
  3. -kQ/d
  4. zero
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Correct answer: (d) zero

Potential is a scalar, and the two equal and opposite contributions cancel at the midpoint.

18.At midpoint P between two +4μc charges. V and E at midpoint P: (NUMS MDCAT 2024)

  1. V=0, E≠0
  2. V=0, E=0
  3. V≠0, E≠0
  4. V≠0, E=0
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Correct answer: (d) V≠0, E=0

The two potentials add and the two fields cancel, so the potential is finite and the field is zero.

All 7 Electric Potential Due to a Point Charge MCQs → Electric Potential Due to a Point Charge notes →

Charging and Discharging of a Capacitor

19.By increasing the area of the plates and decreasing the distance between them, the capacitance of a capacitor: (MDCAT 2020)

  1. increases
  2. decreases
  3. remains unchanged
  4. depends only upon temperature
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Correct answer: (a) increases

$C=\varepsilon_0A/d$ rises with the area and falls with the separation.

20.A capacitor is charged with a battery and the energy stored is $U$. After disconnecting the battery, another capacitor of the same capacity is connected in parallel to the first one. The energy stored in each capacitor is: (MDCAT 2022)

  1. $U/2$
  2. $U/4$
  3. $U$
  4. $2U$
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Correct answer: (b) $U/4$

The charge is shared equally, and $E=Q^2/2C$ with half the charge is a quarter of the energy.

21.A capacitor of capacitance $C$ has a charge $Q$ and stored energy $W$. If the charge is increased to $2Q$, the stored energy will be: (MDCAT 2022)

  1. $2W$
  2. $4W$
  3. $W/4$
  4. $W/2$
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Correct answer: (b) $4W$

$E=Q^2/2C$ goes as the square of the charge.

All 27 Charging and Discharging of a Capacitor MCQs → Charging and Discharging of a Capacitor notes →

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