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WBJEE Equipotential Surfaces — practice questions — page 2

Explore 43 free Equipotential Surfaces questions in WBJEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Equipotential Surfaces questions and exercises with answers

Showing questions 31–43 of 43.

Capacitance changes when DIELECTRIC of relative permittivity K is inserted:Read the answer and worked solution →Energy stored in a capacitor with charge Q and capacitance C:Read the answer and worked solution →Two charges +q and +q are placed at corners of an equilateral triangle. The third corner has potential:Read the answer and worked solution →For a spherical conductor of radius R carrying charge Q, the potential AT THE SURFACE equals:Read the answer and worked solution →Equipotential surfaces around a point charge are:Read the answer and worked solution →Two capacitors 2 µF and 4 µF connected in SERIES across 12 V. Charge on each:Read the answer and worked solution →3 capacitors of 6 µF each in PARALLEL: total capacitance:Read the answer and worked solution →Two charged spheres each of radius R, charge Q, separated by distance d >> R. Force F between them is:Read the answer and worked solution →Potential at center of square (side a) with charges +q, -q, +q, -q at corners (alternating):Read the answer and worked solution →Electric field inside a spherical cavity in a uniformly charged conductor is:Read the answer and worked solution →Find work done to bring a +2 µC charge from infinity to a point where V = 50 V:Read the answer and worked solution →A charged particle q is held at rest in vertical equilibrium in a uniform electric field E pointing upward. Charge-to-mass ratio q/m:Read the answer and worked solution →In a capacitor circuit, when a dielectric is inserted while voltage is HELD CONSTANT by battery, the CHARGE on capacitor:Read the answer and worked solution →

Worked practice questions

Capacitance changes when DIELECTRIC of relative permittivity K is inserted:

  1. Decreases by K
  2. Stays same
  3. Increases by factor K (C → KC)
  4. Becomes zero
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Correct answer: C. Increases by factor K (C → KC)

**With dielectric:** C = Kε₀A/d. Capacitance becomes K times the vacuum value. Energy stored at same voltage also increases (since U = ½CV²).

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Energy stored in a capacitor with charge Q and capacitance C:

  1. Q²/C
  2. Q²/(2C)
  3. CQ²
  4. 2CQ²
Show answer and solution

Correct answer: B. Q²/(2C)

We have U = Q²/(2C). That is U = (1/2)CV². So U = (1/2)QV. Three equivalent forms — useful depending on which two variables you know.

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Two charges +q and +q are placed at corners of an equilateral triangle. The third corner has potential:

  1. 0
  2. kq/r
  3. 2kq/r
  4. kq²/r
Show answer and solution

Correct answer: C. 2kq/r

V is scalar — sum of contributions: V = kq/r + kq/r = 2kq/r. (No vector cancellation issue, unlike fields.)

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