Electrostatic Potential and Capacitance is a Class 12 Physics chapter that carries about 5.0% of the Physics questions in NEET. Practise it with 48 questions covering 2 topics, each with an explanation.
Sample questions on Electrostatic Potential and Capacitance with answers
8 questions from the practice bank, spread across the chapter's topics. The full set is in the app.
Question 1: Capacitance of a Parallel Plate Capacitor
The dielectric strength of a material is the:
- A capacitance per unit area
- B minimum electric field needed to polarise it
- C ratio of its permittivity to that of vacuum
- D maximum electric field it can withstand without breaking down
Answer: D. maximum electric field it can withstand without breaking down
Why: Above this field, the dielectric becomes conducting (breakdown) and sparks occur.
Question 2: Electric Potential due to a Point Charge
The equipotential surfaces in a uniform electric field are:
- A spheres
- B planes parallel to the field
- C cylinders along the field
- D planes perpendicular to the field
Answer: D. planes perpendicular to the field
Why: The field is perpendicular to equipotentials everywhere and points towards decreasing potential.
Question 3: Capacitance of a Parallel Plate Capacitor
The field between the plates of a parallel plate capacitor with a potential difference of 100 V and a separation of 1 cm is:
- A 1 V/m
- B 10⁶ V/m
- C 10² V/m
- D 10⁴ V/m
Answer: D. 10⁴ V/m
Why: E = V/d = 100/0.01 = 10⁴ V/m.
Question 4: Electric Potential due to a Point Charge
The potential at a distance of 0.3 m from a point charge of 3 nC is (k = 9 × 10⁹ N m²/C²):
- A 90 V
- B 27 V
- C 9 V
- D 900 V
Answer: A. 90 V
Why: V = kq/r = 9 × 10⁹ × 3 × 10⁻⁹/0.3 = 90 V.
Question 5: Capacitance of a Parallel Plate Capacitor
Two capacitors of 2 μF and 3 μF are connected in parallel. Their equivalent capacitance is:
- A 6 μF
- B 2.5 μF
- C 5 μF
- D 1.2 μF
Answer: C. 5 μF
Why: Capacitances add in parallel: 2 + 3 = 5 μF.
Question 6: Electric Potential due to a Point Charge
Four equal charges q are placed at the corners of a square of side a. The potential at the centre is:
- A zero
- B 4√2 kq/a
- C 2√2 kq/a
- D 4kq/a
Answer: B. 4√2 kq/a
Why: Each charge is at a distance a/√2, so V = 4 × kq/(a/√2) = 4√2 kq/a.
Question 7: Capacitance of a Parallel Plate Capacitor
When a dielectric slab of constant K completely fills the space between the plates of a parallel plate capacitor, its capacitance becomes:
- A K² times the original
- B 1/K times the original
- C unchanged
- D K times the original
Answer: D. K times the original
Why: C = Kε₀A/d, so filling the gap with a dielectric multiplies the capacitance by K.
Question 8: Electric Potential due to a Point Charge
The work done in moving a charge between two points on the same equipotential surface is:
- A positive
- B zero
- C equal to qE
- D negative
Answer: B. zero
Why: There is no potential difference between the points, so W = qΔV = 0.