Chapter 2: Electrostatic Potential and Capacitance Assertion-Reason Questions | physics Class 12 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): The electrostatic force is a conservative force. Reason (R): The work done by an electrostatic field in moving a charge between two points depends only on the initial and final positions, not on the path.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): The electric potential at the equatorial point of a dipole is maximum. Reason (R): The electric field at the equatorial point is directed along the dipole axis.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): No work is done in moving a test charge along an equipotential surface. Reason (R): Electric field is always perpendicular to equipotential surfaces.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): A conductor placed in an external electric field has zero electric field inside it in the static situation. Reason (R): Free electrons in the conductor redistribute until the net internal field vanishes.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 5

Logic Check

Assertion (A): Inserting a dielectric between the plates of a charged isolated capacitor increases the energy stored. Reason (R): Dielectric insertion increases the capacitance.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 6

Logic Check

Assertion (A): Excess charge given to a conductor resides only on its outer surface. Reason (R): The electric field inside a conductor is zero, so by Gauss's law, no net charge can exist in its interior.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 7

Logic Check

Assertion (A): Capacitors in series have a smaller equivalent capacitance than the smallest individual capacitor. Reason (R): In series, the same charge distributes across all capacitors, causing larger voltage drops across smaller capacitors.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): A bird sitting on a high-voltage transmission line is not electrocuted. Reason (R): The bird's body offers very high resistance to electric current.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 9

Logic Check

Assertion (A): The potential energy of an electric dipole is minimum when its dipole moment is parallel to the external field. Reason (R): U = −pE cosθ is minimised when θ = 0°, giving U = −pE.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): When two charged capacitors at different potentials are connected in parallel, some energy is always lost. Reason (R): The charge redistribution process involves a transient current that dissipates energy as heat and radiation.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): The electric potential varies as 1/r for a point charge and 1/r² for a dipole. Reason (R): A dipole has zero net charge, so its potential falls off faster than that of a monopole.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): The electrostatic potential energy of a system of unlike charges is negative. Reason (R): Work done by an external agent in assembling unlike charges from infinity is negative, since the attractive force assists the assembly.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): Introducing a dielectric between capacitor plates connected to a battery increases the charge stored on the plates. Reason (R): At constant voltage, Q = CV; since C increases with dielectric, Q must also increase.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 14

Logic Check

Assertion (A): The electric field inside a cavity of a conductor is always zero, even if the conductor itself is charged. Reason (R): Any charge placed on the conductor resides only on the outer surface, so the inner surface and cavity region have no charge.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): The equivalent capacitance of capacitors in parallel is always greater than the largest individual capacitance. Reason (R): In parallel combination, the effective plate area increases without changing the separation.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): The energy stored in an electric field is proportional to the square of the field strength. Reason (R): Energy density u = (1/2)ε₀E², derived from the energy stored in a parallel plate capacitor.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 17

Logic Check

Assertion (A): The potential at any point inside a uniformly charged spherical shell equals the potential at its surface. Reason (R): The electric field inside the shell is zero, so no work is done moving a charge inside, implying constant potential.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): In a polar dielectric, the dipoles partially align with the external electric field. Reason (R): Thermal agitation tends to randomise dipole orientations, opposing complete alignment.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 19

Logic Check

Assertion (A): The total charge of a capacitor is zero. Reason (R): A capacitor consists of two conductors carrying charges +Q and −Q, which add to zero.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 20

Logic Check

Assertion (A): The capacitance of a parallel plate capacitor increases when a dielectric slab is partially inserted between the plates. Reason (R): The dielectric partially replaces the air gap, and since K > 1, the effective capacitance increases even for partial insertion.

Reasoning Options

ByteNotes

Chapter sections

Chapter 2: Electrostatic Potential and Capacitance | Assertion-Reason

Assertion (A): The electrostatic force is a conservative force. Reason (R): The work done by an electrostatic field in moving a charge between two points depends only on the initial and final positions, not on the path.

Assertion (A): The electric potential at the equatorial point of a dipole is maximum. Reason (R): The electric field at the equatorial point is directed along the dipole axis.

Assertion (A): No work is done in moving a test charge along an equipotential surface. Reason (R): Electric field is always perpendicular to equipotential surfaces.

Assertion (A): A conductor placed in an external electric field has zero electric field inside it in the static situation. Reason (R): Free electrons in the conductor redistribute until the net internal field vanishes.

Assertion (A): Inserting a dielectric between the plates of a charged isolated capacitor increases the energy stored. Reason (R): Dielectric insertion increases the capacitance.

Assertion (A): Excess charge given to a conductor resides only on its outer surface. Reason (R): The electric field inside a conductor is zero, so by Gauss's law, no net charge can exist in its interior.

Assertion (A): Capacitors in series have a smaller equivalent capacitance than the smallest individual capacitor. Reason (R): In series, the same charge distributes across all capacitors, causing larger voltage drops across smaller capacitors.

Assertion (A): A bird sitting on a high-voltage transmission line is not electrocuted. Reason (R): The bird's body offers very high resistance to electric current.

Assertion (A): The potential energy of an electric dipole is minimum when its dipole moment is parallel to the external field. Reason (R): U = −pE cosθ is minimised when θ = 0°, giving U = −pE.

Assertion (A): When two charged capacitors at different potentials are connected in parallel, some energy is always lost. Reason (R): The charge redistribution process involves a transient current that dissipates energy as heat and radiation.

Assertion (A): The electric potential varies as 1/r for a point charge and 1/r² for a dipole. Reason (R): A dipole has zero net charge, so its potential falls off faster than that of a monopole.

Assertion (A): The electrostatic potential energy of a system of unlike charges is negative. Reason (R): Work done by an external agent in assembling unlike charges from infinity is negative, since the attractive force assists the assembly.

Assertion (A): Introducing a dielectric between capacitor plates connected to a battery increases the charge stored on the plates. Reason (R): At constant voltage, Q = CV; since C increases with dielectric, Q must also increase.

Assertion (A): The electric field inside a cavity of a conductor is always zero, even if the conductor itself is charged. Reason (R): Any charge placed on the conductor resides only on the outer surface, so the inner surface and cavity region have no charge.

Assertion (A): The equivalent capacitance of capacitors in parallel is always greater than the largest individual capacitance. Reason (R): In parallel combination, the effective plate area increases without changing the separation.

Assertion (A): The energy stored in an electric field is proportional to the square of the field strength. Reason (R): Energy density u = (1/2)ε₀E², derived from the energy stored in a parallel plate capacitor.

Assertion (A): The potential at any point inside a uniformly charged spherical shell equals the potential at its surface. Reason (R): The electric field inside the shell is zero, so no work is done moving a charge inside, implying constant potential.

Assertion (A): In a polar dielectric, the dipoles partially align with the external electric field. Reason (R): Thermal agitation tends to randomise dipole orientations, opposing complete alignment.

Assertion (A): The total charge of a capacitor is zero. Reason (R): A capacitor consists of two conductors carrying charges +Q and −Q, which add to zero.

Assertion (A): The capacitance of a parallel plate capacitor increases when a dielectric slab is partially inserted between the plates. Reason (R): The dielectric partially replaces the air gap, and since K > 1, the effective capacitance increases even for partial insertion.

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