CLASS XII
ASSERTION REASON QUESTIONS
Two statements are given below. One is labelled Assertion (A) and the other is labelled Reason (R). Read the statements carefully and choose the option that correctly describes statements A and R.
A. Both assertion and reason are true and reason is the correct explanation for assertion.
B. Both assertion and reason are true but reason is not the correct explanation of assertion.
C. Assertion is true but reason is false.
D. Assertion is false but the reason is true.
E. Assertion is false and reason is also false.
CHAPTER 1
Electric Charges and Fields
Assertion (A): An electric dipole is in stable equilibrium when placed in a uniform electric field with its dipole moment opposite to the field. Reason (R): No torque acts on an electric dipole when its dipole moment is in a direction opposite to the field.
Assertion (A): A point charge is brought in an electric field at a nearby point will increase or decrease depending on the nature of charge.
Reason (R): Electric field is independent of the nature of charge.
Assertion (A): Range of Coulomb force is infinite.
Reason (R): Coulomb force acts between two charged particles.
Assertion (A): If a conducting medium is placed between two charges, then electric force between them becomes zero.
Reason (R): Reduction in force due to introduced material is inversely proportional to its dielectric constant.
Assertion (A): If there exists coulomb attraction between two bodies, both of them may not be charged.
Reason (R): In coulombic attraction two bodies are oppositely charged.
Assertion (A): The electric flux emanating out and entering a closed surface are 8x103 and 2x103 Vm respectively. The charge enclosed by the surface is 0.053µC.
Reason (R): Gauss’s theorem in electrostatics may be applied to verify.
Assertion (A): The electric lines of force diverge from a positive charge and converge at a negative charge.
Reason (R): A charged particle free to move in an electric field always moves along an electric line of force.
Assertion (A): Coulomb’s force is the dominating force in the universe.
Reason (R): Coulomb’s force is weaker than gravitational force.
Assertion (A): Electrostatic field lines start at positive charges and end at negative charges.
Reason (R): Field lines are continuous curves without any breaks and they form a closed loop.
Assertion (A): The charge given to a metallic sphere does not depend on whether it is hollow or solid.
Reason (R): Since the charge resides only on the surface of the conductor.
Assertion (A): Charge is quantized because only an integral number of electrons can be transferred.
Reason (R): There is no possibility of transfer of some fraction of electrons.
Assertion (A): Coulomb force and gravitational force follow the same inverse-square law.
Reason (R): Both laws are same in all aspects
Assertion (A): Electrostatic field lines start at positive charges and end at negative charges.
Reason (R): Field lines are continuous curves without any breaks and they form closed loops.
Assertion(A): Electrons move away from a region of lower potential to a region of higher potential.
Reason (R): An electron has a negative charge.
Assertion(A): If a proton and an electron are replaced in the same uniform electric field, they experience different acceleration.
Reason (R): Electric force on a test charge is independent of its mass.
Assertion(A): Units of electric dipole moment are Cm and units of torque are Nm.
Reason (R): Electric dipole moment and torque are given by
p = q (2a) and τ = force × distance, respectively.
Assertion(A): When a body acquires negative charge, its mass decreases.
Reason (R): A body acquires positive charge when it gains electrons.
Assertion(A): Surface charge density of an irregularly shaped conductor in non-uniform.
Reason (R): Surface density is defined as charge per unit area.
Assertion(A): Total flux through a closed surface is zero if no charge is enclosed by the surface.
Reason (R): Gauss law is true for any closed surface, no matter what its shape or size is.
Assertion(A): A metallic shield in the form of a hollow shell may be built to block an electric field.
Reason (R): In a hollow spherical shield, the electric field inside it is zero at every point.
ANSWER KEY
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