Electric Field Due to an Infinite Sheet of Charge

Electric Field Due to an Infinite Sheet of Charge MDCAT MCQs with answers

15 past paper MCQs on Electric Field Due to an Infinite Sheet of Charge, from the Electrostatics unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.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, $E=\sigma/\varepsilon_0$.

2.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.

3.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.

4.149.Electric intensity between two oppositely charge plates in the middle region is_______ (UHS MDCAT 2024)

  1. Non-uniform
  2. Uniform
  3. Cannot be predicted
  4. Variable
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Correct answer: (b) Uniform

Between two large parallel plates the field lines are straight and evenly spaced, so the field is uniform.

5.Gauss law cannot be used to find which of the following quantity? (UHS MDCAT 2023)

  1. Electric field intensity
  2. Electric flux density
  3. Charge
  4. Permittivity
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Correct answer: (d) Permittivity

Permittivity is a property of the medium and must be known before Gauss’s law can be used at all.

6.Electric intensity due to charge distributions are calculated using which following law? (SZABMU MDCAT 2023)

  1. Ohm’s law
  2. Faraday’s law
  3. Gauss’s law
  4. Ampere’s law
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Correct answer: (c) Gauss’s law

Gauss’s law gives the field of a symmetrical charge distribution from the flux through a closed surface.

7.Electric field intensity inside a hollow charged sphere is: (UHS MDCAT 2023)

  1. Maximum
  2. Zero
  3. Negative
  4. Positive
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Correct answer: (b) Zero

The charge sits on the surface, so by Gauss’s law the field inside the shell is zero.

8.The flux through a surface will be zero when angle between E and △A is: (PMC MDCAT 2022)

  1. 90o
  2. 60o
  3. 30o
  4. 0o
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Correct answer: (a) 90o

Flux is $EA\cos\theta$, which vanishes when the field lies along the surface.

9.Charge inside conductor is: (PMC MDCAT 2022)

  1. Possible
  2. Can be greater than zero
  3. Zero
  4. Negative always
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Correct answer: (c) Zero

Charge on a conductor sits on its outer surface, so the interior encloses none.

10.The number of field lines passing through a certain element of area is known as: (PMC MDCAT 2022)

  1. Electric flux through that area
  2. Electric current through that area
  3. voltage through that area
  4. Amperes through that area
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Correct answer: (a) Electric flux through that area

The number of field lines crossing an area is the electric flux through it.

11.The electric flux through a closed surface depends upon the: (PMC MDCAT 2022)

  1. Size of the surface
  2. Shape of the surface
  3. Position of charge enclosed in the surface
  4. Magnitude of charge enclosed in the surface
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Correct answer: (d) Magnitude of charge enclosed in the surface

By Gauss’s law the flux out of a closed surface depends only on the charge inside it.

12.The electric flux through the surface of the sphere is directly proportional to the: (PMC MDCAT 2022)

  1. Surface area of the sphere
  2. Radius of the sphere
  3. Charge at the centre of the sphere
  4. Nature of charge
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Correct answer: (c) Charge at the centre of the sphere

By Gauss’s law the flux out of a closed surface is the enclosed charge over $\varepsilon_0$.

13.Electric Flux through the surface of a sphere which has constant charge at its centre depends on: (PMC MDCAT 2022)

  1. The radius of the sphere
  2. The surface area of the sphere
  3. The amount of charge inside the sphere
  4. The amount of charge outside the sphere
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Correct answer: (c) The amount of charge inside the sphere

By Gauss’s law only the enclosed charge matters, not the size of the surface.

14.The flux through a surface will be minimum when angle between E and △A is: (PMC MDCAT 2022)

  1. 90°
  2. 60°
  3. 30°
  4. 0o
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Correct answer: (a) 90°

Flux is $EA\cos\theta$, which falls to zero when the field lies along the surface.

15.Electric field strength at a point between oppositely charged plates is ‘E’. If the distance between plates is reduced to half, what will be the new value of electric intensity? (UHS MDCAT 2019)

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

$E=V/d$ between parallel plates, so halving the separation doubles the field.

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