# Assertion Reason Physics Chapter 2 Electrostatic Potential and Capacitance

Questions of Assertion Reason of Physics Chapter 2 Electrostatic Potential and Capacitance CBSE Class 12 are very simple to understand as this chapter deals with Electrostatic Potential and Capacitance To solve assertion reason type questions of Physics, a deeper understanding of concept about Electrostatic Potential, Potential due to a Point Charge, Potential due to an Electric Dipole, Potential due to a System of Charges, Equipotential Surfaces, Potential Energy of a System of Charges, Potential Energy in an External Field, Electrostatics of Conductors, Dielectrics and Polarisation, Capacitors and Capacitance, The Parallel Plate Capacitor, Effect of Dielectric on Capacitance, Combination of Capacitors and Energy Stored in a Capacitor is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.

How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.

How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.

In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:

Assertion (A)Reason (R)MCQ Options (Fixed for all questions)
If TrueTrue(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
If TrueTrue(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
If TrueFalse(c) Assertion (A) is true but reason (R) is false.
If FalseTrue(d) Assertion (A) is false but reason (R) is true.
If FalseFalse(e) Both Assertion and Reason are false.

Now, lets practice some Assertion Reason Questions of Physics: Chapter 2 Electrostatic Potential and Capacitance

For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.

Question.1.
Assertion: If the distance between parallel plates of a capacitor is halved and dielectric constant is three times, then the capacitance becomes 6 times.
Reason: Capacity of the capacitor does not depend upon the nature of the material.

Ans.1. (c)
A is true but R is false.

Question.2.
Assertion: A parallel plate capacitor is connected across battery through a key. A dielectric slab of dielectric constant K is introduced between the plates. The energy which is stored becomes K times.
Reason: The surface density of charge on the plate remains constant or unchanged.

Ans.2. (c)
A is true but R is false.

Question.3.
Assertion: The total charge stored in a capacitor is zero.
Reason: The field just outside the capacitor is \frac{\sigma}{\epsilon_{0}} where σ is the charge density.

Ans.3. (c)
A is true but R is false.

Question.4.
Assertion: The electrostatic force between the plates of a charged isolated capacitor decreases when dielectric fills whole space between plates.
Reason: The electric field between the plates of a charged isolated capacitance increases when dielectric fills whole space between plates.

Ans.4. (d)
A is false but R is true.

Question.5.
Assertion: Two concentric charged shells are given. The potential difference between the shells depends on charge of inner shell.
Reason: Potential due to charge of outer shell remains same at every point inside the sphere.

Ans.5. (a)
Both A and R are true and R is correct explanation of the assertion.

Question.6.
Assertion: Two equipotential surfaces cannot cut each other.
Reason: Two equipotential surfaces are parallel to each other.

Ans.6. (c)
A is true but R is false.

Question.7.
Assertion: The potential difference between any two points in an electric field depends only on initial and final position.
Reason: Electric field is a conservative field so the work done per unit positive charge does not depend on path followed.

Ans.7. (a)
Both A and R are true and R is correct explanation of the assertion.

Question.8.
Assertion: Electric field inside a conductor is zero.
Reason: The potential at all the points inside a conductor is same.

Ans.8. (b)
Both A and R are true but R is not the correct explanation of the assertion.

Question.9.
Assertion: Electric field is discontinuous across the surface of a spherical charged shell.
Reason: Electric potential is continuous across the surface of a spherical charged shell.

Ans.9. (b)
Both A and R are true but R is not the correct explanation of the assertion.

Question.10.
Assertion: Work done in moving a charge between any two points in an electric field is independent of the path followed by the charge, between these points.
Reason: Electrostatic force is a non conservative force.

Ans.10. (c)
A is true but R is false.

Question.11.
Assertion: Two adjacent conductors of unequal dimensions, carrying the same positive charge have a potential difference between them.
Reason: The potential of a conductor depends upon the charge given to it.

Ans.11. (b)
Both A and R are true but R is not the correct explanation of the assertion.

Question.12.
Assertion: Electric potential and electric potential energy are different quantities.
Reason: For a system of positive test charge and point charge electric potential energy = electric potential.

Ans.12. (c)
Potential and potential energy are different quantities and cannot be equated.

Question.13.
Assertion: For a non-uniformly charged thin circular ring with net charge is zero, the electric field at any point on axis of the ring is zero.
Reason: For a non-uniformly charged thin circular ring with net charge zero, the electric potential at each point on axis of the ring is zero.

Ans.13. (d)
For a non-uniformly charged thin circular ring with net zero charge, electric potential at each point on its axis is zero. Hence electric field at each point on its axis must be perpendicular to the axis. Therefore Assertion is false and Reason is true.

Question.14.
Assertion: For a charged particle moving from point P to point Q, the net work done by an electrostatic field on the particle is independent of the path connecting point P to point Q.
Reason: The net work done by a conservative force on an object moving along a closed loop is zero.

Ans.14. (a)
Both A and R are true and R is correct explanation of the assertion.

Question.15.
Assertion: Polar molecules have permanent dipole moment.
Reason: In polar molecules, the centres of positive and negative charges coincide even when there is no external field.

Ans.15. (c)
A is true but R is false.

Question.16.
Assertion: Dielectric polarisation means formation of positive and negative charges inside the dielectric.
Reason: Free electrons are formed in this process.

Ans.16. (c)
A is true but R is false.

Question.17.
Assertion: In the absence of an external electric field, the dipole moment per unit volume of a polar dielectric is zero.
Reason: The dipoles of a polar dielectric are randomly oriented.

Ans.17. (a)
Both A and R are true and R is correct explanation of the assertion.

Question.18.
Assertion: For a point charge, concentric spheres centered at a location of the charge are equipotential surfaces.
Reason: An equipotential surface is a surface over which potential has zero value.

Ans.18. (c)
A is true but R is false.

Question.19.
Assertion: Electric energy resides out of the spherical isolated conductor.
Reason: The electric field at any point inside the conductor is zero.

Ans.19. (a)
As these is no electric field inside the conductor, and so no energy inside it.

Question.20.
Assertion: Two equipotential surfaces cannot cut each other.
Reason: Two equipotential surfaces are parallel to each other.

Ans.20. (c)
Reason is false because the work done in bringing a unit positive charge from infinity to a point in equatorial plane is equal and opposite for the two charges of the dipole.

Question.21.
Assertion: Two equipotential surfaces can be orthogonal.
Reason: Electric field lines are normal to the equipotential surface.

Ans.21. (d)
Two equipotential surfaces never intersect each other so they cannot be orthogonal.

Question.22.
Assertion: The equatorial plane of a dipole is an equipotential surface.
Reason: The electric potential at any point on equatorial plane is zero.

Ans.22. (b)
Both A and R are true but R is not the correct explanation of the assertion.

Question.23.
Assertion: The electric potential at any point on the equatorial plane of a dipole is zero.
Reason: The work done in bringing a unit positive charge from infinity to a point in equatorial plane is equal for the two charges of the dipole.

Ans.23. (d)
A is false but R is true.

Question.24.
Assertion: A parallel plate capacitor is connected across battery through a key. A dielectric slab of dielectric constant k is introduced between the plates. The energy stored becomes k times.
Reason: The surface density of charge on the plate remains constant.

Ans.24. (c)
A is true but R is false.

Question.25.
Assertion: Two metal plates having charges Q, face each other at some separation and are dipped into an oil tank. If the oil is pumped out, the electric field between the plates increases.
Reason: Electric field between the plates, E_{med}=\frac{E_{air}}{K} .

Ans.25. (c)
A is true but R is false.

Question.26.
Assertion: When a dielectric slab is gradually inserted between the plates of an isolated parallel-plate capacitor, the energy of the system decreases.
Reason: The force between the plates decreases.

Ans.26. (c)
A is true but R is false.

Question.27.
Assertion: A dielectric is inserted between the plates of a battery connected capacitor. The energy of the capacitor increases.
Reason: Energy of the capacitor, U=\frac{CV^{2}}{2} .

Ans.27. (a)
Both A and R are true and R is correct explanation of the assertion.