Download App

Physics Assertion (A) & Reason (B) MCQ

Electrostatic Potential and Capacitance · Rajasthan Board (RBSE) STD 12 Science (Rajasthan - English Medium). 20 questions.

Questions

Assertion (A) & Reason (B) MCQ

Take a timed test

20 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Positive charge always moves from a higher potential point to a lower potential point.
Reason (R): Electric potential is a vector quantity.
Answer
  1. A is true, but R is false.
Explanation:
If two points P and Q in an electric field are separated by an infinitesimal distance $\triangle\text{x}$ and have a potential difference $\triangle\text{V}$ between then, $\text{E}=\frac{-\triangle\text{V}}{\triangle\text{x}}.$
Here negative sign implies that $\vec{\text{E}}$ has got a direction opposite to the potential gradient i.e. in the direction of $\vec{\text{E}}$ the potential decreases i.e. positive charge always move from a higher potential point to a lower potential point.
View full question & answer→
Question 21 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): The surface of a conductor is an equipotential surface.
Reason (R): Conductor allows the flow of charge.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
Explanation:
lf two points on a conductor were at different potentials, charge would flow from higher potential to lower potentials, till their potentials become equal. A surface on which the potential has the same value everywhere is called an equipotential surface.
View full question & answer→
Question 31 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): A capacitor is connected to a battery. If we move its plate further apart, work will be done against the electrostatic attraction between the plates, and the energy of the capacitor gets decreased.
Reason (R): The energy stored in capacitor is dissipated in the form of heat energy.
Answer
  1. Both A and R are true, but R is not the correct explanation of A.
Explanation:
When the plates of a capacitor are moved further apart, the capacitance gets decreased. As battery remains connected, hence charge q( = CV) on the plates is decreased, and energy $\text{U}=\Big[\frac{1}{2}\text{CV}^2\Big]$ also decreases. Some charge from the plates flows to the battery i.e. some energy of capacitor is transferred to the battery. Work done against electrostatic attraction between plates is used in the transference of energy and is dissipated in the form of heat energy in connection wires.
View full question & answer→
Question 41 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): The whole charge of a conductor cannot be transferred to another isolated conductor.
Reason (R): The total transfer of charge from one to another is not possible.
Answer
  1. A is false, and R is also false.
Explanation:
The whole charge of a conductor can be transferred to another isolated conductor, if it is placed inside the hollow insulated conductor and connected with it.
View full question & answer→
Question 51 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): When a dielectric medium is filled between the plates of a condenser, its capacitance increases.
Reason (R): The dielectric medium reduces the potential difference between the plates of the condenser.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
Explanation:
The dielectric molecules are polarised, producing an opposite electric field. Thus the effective electric field and hence the potential difference between the plates is reduced and consequently, the capacitance is increased $\big(\because\text{C}=\frac{\text{Q}}{\text{V}}\big).$
View full question & answer→
Question 61 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Two adjacent conductors, carrying the same positive charge have no potential difference between them.
Reason (R): The potential of a conductor does not depend upon the charge given to it.
Answer
  1. A is false, and R is also false.
Explanation:
The potential of a conductor depends upon the charge given to it and there exist a potential different between two adjacent conductors.
View full question & answer→
Question 71 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Charge on all the condensers connected in series is the same.
Reason (R): Capacitance of capacitor is directly proportional to charge on it.
Answer
  1. A is true, but R is false.
Explanation:
Let two capacitors be connected in series. If +q charge is installed on left plate of the first capacitor then -q charge is induced on right plate of this capacitor. This charge comes from electron drawn from the left plate of second capacitor. Thus there will be equal charge +q on the left plate of second capacitor and -q charge induced on the right plate of second capacitor. Thus each capacitor has same charge (q) when connected in series. Capacitance is quantity dependent on construction of capacitor and independent of charge.
View full question & answer→
Question 81 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Lines of force are perpendicular to conductor surface.
Reason (R): Generally electric field is perpendicular to equipotential surface.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
View full question & answer→
Question 91 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Increasing the charge on the plates of a capacitor means increasing the capacitance.
Reason (R): Capacitance is directly proportional to charge.
Answer
  1. A is false, and R is also false.
Explanation:
On increasing the charge, potential increases. But capacity of a capacitor is fixed by geometry of condenser $\Big(\text{C}=\frac{\epsilon_0\text{A}}{\text{d}}\Big).$ Capacitance is independent of charge.
View full question & answer→
Question 101 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Circuits containing capacitors should be handled cautiously even when there is no current.
Reason (R): The capacitors are very delicate and so quickly breakdown.
Answer
  1. A is true, but R is false.
Explanation:
A charged capacitor, after removing the battery, does not discharge itself. If this capacitor is touched by someone, he may feel shock due to large charge still present on the capacitor. Hence it should be handled cautiously otherwise this may cause a severe shock.
View full question & answer→
Question 111 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): A capacitor can be broken by placing large amount of charge on it.
Reason (R): After breakage potential, the capacitor is destroyed.
Answer
  1. Both A and R are true, but R is not the correct explanation of A.
Explanation:
When large amount of charges are placed on capacitor a high potential difference is established between its conducting components. If this potential difference is above what is called breakage potential, an electric discharge results, destroying the capacitor. If the capacitor contains an insulator between its conducting components, the insulator will be burnt at the atomic/ molecular level. A capacitor subjected to voltage exceeding the breakage potential cannot be recovered. It should be discarded and replaced.
View full question & answer→
Question 121 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): No work is done in taking a positive charge from one point to other inside a positively charged metallic sphere while outside the sphere work is done in taking the charge toward the sphere.
Reason (R): Inside the sphere electric potential is same at each potential, but outside it is different for different points.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
Explanation:
Inside the charged metallic sphere every point is at the same electric potential, hence $\text{W}=\text{q}\triangle\text{V}=0.$ But outside the sphere, there exists a potential gradient at every point, hence $\text{W}\not=0.$
View full question & answer→
Question 131 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): An applied electric field will polarize the polar dielectric material.
Reason (R): In polar dielectrics, each molecule has a permanent dipole moment but these are randomly oriented in the absence of an externally applied electric field.
Answer
  1. Both A and R are true, but R is not the correct explanation of A.
Explanation:
If a material contain polar molecules, they will generally be in random orientations when no electric field is applied. An applied electric field will polarize the material by orienting the dipole moment of polar molecules.
View full question & answer→
Question 141 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): When air between the plates of a parallel plate condenser is replaced by an insulating medium of dielectric constant its capacity increases.
Reason (R): Electric field intensity between the plates with dielectric in between it is reduced.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
Explanation:
The capacity of a parallel plate condenser is given by,
$\text{C}=\frac{\text{q}}{\text{V}}$ (i)
Electric field intensity becomes $\frac{1}{\text{K}}$ times [as $\text{K}=\frac{\text{E}_0}{\text{E}},$] therefore potential V also becomes $\frac{1}{\text{K}}$ times.
Hence, from equation (i) capacity, becomes K times. Thus electric field decreases and capacitance increases when condenser is filled with insulated medium of some dielectric constant.
View full question & answer→
Question 151 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Conductors having equal positive charge and volume, must also have same potential.
Reason (R): Potential depends only on charge and volume of conductor.
Answer
  1. A is false, and R is also false.
Explanation:
Electric potential of a charged conductor depends not only on the amount of charge and volume but also on the shape of the conductor. Hence if their shapes are different, they may have different electric potential.
View full question & answer→
Question 161 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): The dielectric constant for metals is infinity.
Reason (R): When a charged capacitor is filled completely with a metallic slab, its capacity becomes very large.
Answer
  1. A is true, but R is false.
Explanation:
The capacitance of a capacitor filled partially with a dielectric of thickness t given by,
$\text{C}=\frac{\epsilon_0\text{A}}{\text{d-t}[1-\frac{1}{\text{K}}]}$
For metals, $\text{K}=\infty,$ $\therefore\text{C}=\frac{\epsilon_0\text{A}}{\text{d-t}}.$
Now if the capacitor is filled completely with a metallic slab, then t = d, $\therefore\text{C}=\infty$ i.e., when a charged capacitor filled fully with a metallic slab, then capacitor is short circuited i.e., it will no more work as a capacitor.
View full question & answer→
Question 171 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Capacity of a parallel plate capacitor increases when distance between the plates is decreased.
Reason (R): Capacitance of capacitor is inversely proportional to distance between them.
Answer
  1. Both A and R are true, and R is the correct explanation of A.
Explanation:
Capacitance of parallel plate capacitor is
$\text{C}=\frac{\epsilon_0\text{A}}{\text{d}}.$ Thus distance decreases and capacitance of capacitor increases.
View full question & answer→
Question 181 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): If the distance between parallel pates of a capacitor is halved and dielectric constant is made three times, then the capacitance becomes six times.
Reason (R): Capacitance of the capacitor does not depend upon the nature of the material of the plates.
Answer
  1. A is true, but R is false.
Explanation:
The capacitance C, with dielectric between the plates, is given as
$\text{C}=\frac{\epsilon_0\text{KA}}{\text{d}}$
As, $\text{d'}=\frac{\text{d}}{2}\text{K'}=\text{3K},$ then new capacitance becomes
$\text{C'}=\frac{\epsilon_0\text{3KA}}{\frac{\text{d}}{2}}$
$\Rightarrow\text{C'}=\frac{6\epsilon\text{KA}}{\text{d}}=\text{6C}$
The capacitance C depends only on the geometrical configuration (shape, size, separation) of the system of two conductors.
View full question & answer→
Question 191 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube.
Reason (R): Electric field requires low voltage.
Answer
  1. A is false, and R is also false.
Explanation:
If electric field is used for detecting the electron beam, then very high voltage will have to be applied and very long tube will have to be taken.
View full question & answer→
Question 201 Mark
For 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.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion (A): Electric potential of the earth is zero.
Reason (R): The electric field due to the earth is zero.
Answer
  1. A is true, but R is false.
Explanation:
Earth is a good conductor of very large size. When some small charge is given to earth, its potential does not change. Hence potential of earth is assumed to be zero. It is just like sea level which does not alter materially when water is added to it or removed from it. Thus, the potential of all other bodies are measured with reference to the earth. Forth is, if the connection of a charged body to the ground by a metallic conductor would cause electrons to flow to that body from ground, the body is at positive potential. Conversely, is also true. ln either case the conductor is neutralized and brought to zero potential. ln fact the atmosphere does possess significant electric field.
View full question & answer→
Generate Paper FreeAll Electrostatic Potential and Capacitance topics