Q.1 The capacitance of a parallel plate capacitor depends on:
Area of plates and distance between them
Voltage applied
Charge stored
Material of connecting wires
Explanation - Capacitance is given by C = ε₀εr A/d, so it depends on plate area (A), separation (d), and dielectric constant (εr).
Correct answer is: Area of plates and distance between them
Q.2 Unit of capacitance is:
Coulomb
Farad
Henry
Ohm
Explanation - Capacitance is defined as charge stored per unit potential difference. Its SI unit is Farad (F).
Correct answer is: Farad
Q.3 When a dielectric is inserted between the plates of a capacitor, the capacitance:
Increases
Decreases
Remains same
Becomes zero
Explanation - A dielectric increases the ability of the capacitor to store charge, so capacitance increases.
Correct answer is: Increases
Q.4 The energy stored in a capacitor is given by:
½ CV²
CV
Q²/2C
Both ½ CV² and Q²/2C
Explanation - Energy can be expressed in multiple forms: U = ½ CV² = Q²/2C = ½ QV.
Correct answer is: Both ½ CV² and Q²/2C
Q.5 Which of the following does NOT affect the capacitance of a capacitor?
Plate area
Plate separation
Dielectric constant
Applied voltage
Explanation - Capacitance is a geometrical property and depends only on area, distance, and dielectric. Voltage only affects charge stored.
Correct answer is: Applied voltage
Q.6 Dimension of capacitance is:
M⁻¹L⁻²T⁴A²
ML²T⁻²
M¹L¹T⁻³
M⁰L²T²
Explanation - Capacitance dimension is derived from Q/V = (IT)/(ML²T⁻³A⁻¹), simplifying to M⁻¹L⁻²T⁴A².
Correct answer is: M⁻¹L⁻²T⁴A²
Q.7 If a capacitor is charged and then disconnected from the battery, inserting a dielectric will:
Increase potential difference
Decrease potential difference
Not change potential difference
Remove charge
Explanation - Since charge is constant, capacitance increases, so V = Q/C decreases.
Correct answer is: Decrease potential difference
Q.8 In series combination of capacitors, the equivalent capacitance is:
Greater than individual capacitors
Less than smallest capacitor
Equal to sum
Cannot be determined
Explanation - For series combination, 1/Ceq = 1/C1 + 1/C2 + …, so Ceq is less than the smallest capacitor.
Correct answer is: Less than smallest capacitor
Q.9 Which quantity is continuous across a dielectric boundary?
Electric field
Displacement vector D⊥
Potential
Charge density
Explanation - Electric potential is always continuous; electric field can be discontinuous across dielectric boundary.
Correct answer is: Potential
Q.10 Work done to charge a capacitor is stored as:
Kinetic energy
Magnetic energy
Electrostatic potential energy
Chemical energy
Explanation - Energy supplied is stored in the electric field between the plates as electrostatic energy.
Correct answer is: Electrostatic potential energy
Q.11 A capacitor of 10 μF is charged to 100 V. The energy stored is:
0.05 J
0.5 J
50 J
5 J
Explanation - U = ½ CV² = ½ × 10×10⁻⁶ × (100)² = 0.05 J.
Correct answer is: 0.05 J
Q.12 Capacitance of an isolated spherical conductor is proportional to:
Square of radius
Inverse of radius
Radius
Not dependent on radius
Explanation - Capacitance of a sphere = 4πε₀R, directly proportional to radius.
Correct answer is: Radius
Q.13 A parallel plate capacitor filled with dielectric has capacitance C. If dielectric is removed, new capacitance will be:
Cεr
C/εr
C²
εr² C
Explanation - Dielectric increases capacitance by εr. Removing it reduces capacitance by the same factor.
Correct answer is: C/εr
Q.14 If two capacitors 6 μF and 12 μF are in series, equivalent capacitance is:
18 μF
4 μF
2 μF
3 μF
Explanation - 1/Ceq = 1/6 + 1/12 = 1/4 → Ceq = 4 μF.
Correct answer is: 4 μF
Q.15 A capacitor blocks:
Direct current
Alternating current
Both
Neither
Explanation - A capacitor does not allow steady DC but allows AC due to charging/discharging.
Correct answer is: Direct current
Q.16 Which of the following has the highest dielectric constant?
Vacuum
Air
Water
Glass
Explanation - Water has a very high dielectric constant (~80), much higher than air or glass.
Correct answer is: Water
Q.17 What happens when two capacitors are connected in parallel?
Voltage is different
Charge divides inversely
Capacitance adds up
Equivalent is less than smallest
Explanation - In parallel, Ceq = C1 + C2 + … because voltage across each is the same.
Correct answer is: Capacitance adds up
Q.18 If separation between capacitor plates is doubled, capacitance:
Becomes half
Becomes double
Remains same
Becomes zero
Explanation - Capacitance C = ε₀A/d, so doubling d halves capacitance.
Correct answer is: Becomes half
Q.19 A 2 μF capacitor and 3 μF capacitor are in parallel. Their equivalent is:
1.2 μF
5 μF
6 μF
0.6 μF
Explanation - In parallel, capacitances add: Ceq = 2 + 3 = 5 μF.
Correct answer is: 5 μF
Q.20 Capacitance of cylindrical capacitor depends on:
Length and radii of cylinders
Material of wire
Battery voltage
None of these
Explanation - Cylindrical capacitance depends on length, inner radius, outer radius, and dielectric.
Correct answer is: Length and radii of cylinders
Q.21 The dielectric strength of a material refers to:
Its capacitance
Its resistance
Maximum electric field it can withstand
Charge storing capacity
Explanation - Dielectric strength is the maximum electric field before breakdown occurs.
Correct answer is: Maximum electric field it can withstand
Q.22 Which of these capacitors can store the most energy for the same voltage?
1 μF
2 μF
3 μF
5 μF
Explanation - Energy = ½ CV². For same V, higher capacitance stores more energy.
Correct answer is: 5 μF
Q.23 When a capacitor is fully charged through a DC battery:
Current is maximum
Current is zero
Voltage is zero
Both voltage and current are zero
Explanation - At steady state in DC, capacitor behaves as open circuit, so current stops.
Correct answer is: Current is zero
Q.24 Which instrument is used to measure capacitance?
Voltmeter
Capacitance meter
Ammeter
Galvanometer
Explanation - Capacitance meters are designed to measure capacitance directly.
Correct answer is: Capacitance meter
Q.25 Inserting a conductor between plates of a capacitor (not touching either plate) will:
Increase capacitance
Decrease capacitance
Not affect capacitance
Make capacitance infinite
Explanation - Conductor reduces effective distance and increases capacitance.
Correct answer is: Increase capacitance