NCERT Class 12 Physics Chapter 2 Notes Electrostatic Potential and Capacitance - Download PDF

NCERT Class 12 Physics Chapter 2 Notes Electrostatic Potential and Capacitance - Download PDF

Edited By Vishal kumar | Updated on Jan 23, 2024 11:14 AM IST

NCERT Notes for CBSE Class 12 Physics Chapter 2 Electrostatic Potential and Capacitance - Download Free PDF

A solid understanding of fundamental concepts is essential for effective preparation in board exams, state exams, and competitive exams such as JEE and NEET. Comprehensive Electrostatic Potential and Capacitance class 12 notes are essential for efficiently revising chapters.

With this in mind, Careers360's dedicated team has created CBSE class 12 physics ch 2 notes. These notes are an invaluable resource for students who want to speed up their revision for class tests and exams.

These meticulously crafted physics class 12 chapter 2 notes pdf not only cover the fundamental concepts but also present critical formulas and practical insights in a clear manner. For a confident and successful exam journey, boost your preparation with Careers360's Electrostatic Potential and Capacitance notes class 12.

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NCERT Class 12 Physics Chapter 2 Notes

Electric Potential:

The electrostatic potential in a region of the electric field is equal to the amount of work done in bringing a unit-positive test charge from infinity to that point against the electrostatic force.

V=\frac{w}{q_0}1625209592922

Where,

w - work done and q0 - unit charge

  • Electric potential is a scalar quantity and the SI unit is Volt (V).
  • CGS unit is stat volt.
  • Dimension - mL^{2}T^{-3}A^{-1}1625209593076.

1volt=\frac{1}{300}1625209593225 stat volt.

Potential due to system of point charges:

V=\sum_{i=1}^{n}\frac{KQ_i}{r_i}1625209593381

16252096039481625209593536

Potential difference:

The potential difference between two points A and B in an electric field is equal to the amount of work done (by an external agent) in moving a unit positive charge from point A to another point B.

V_B-V_A=\frac{w}{q}1625209593682

Where,

W is the amount of work done and q is the unit positive charge.

Electric potential due to a point charge:

\\V=K\frac{q}{r}\\K=\frac{1}{4\pi\epsilon_0}1625209593837

Electric Potential Energy:

Consider a system with two charges, q1 and q2 fixed at points A and B, respectively, and separated by AB =r2. If q2 is moved from B to a new point C along AB and AC =r2, and the charge is displaced from r to r + dr, then the work done (dW) is as follows:

dw=F.dr

\\=\frac{Kq_1q_2}{r^2}.dr1625209593999

  • Total work done
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\\W=\int_{r_1}^{r_2}\frac{Kq_1q_2}{r^2}.dr\\=\frac{q_1q_2}{4\pi\ \epsilon_0}[\frac{1}{r_1}-\frac{1}{r_2}]1625209594173

  • Change in potential energy

U(r_2)-U(r_1)=-W1625209594329

\\=\frac{q_1q_2}{4\pi\ \epsilon_0}[\frac{1}{r_2}-\frac{1}{r_1}]1625209594492

  • When the system of two charges have infinite separation then potential energy

U(\infty)=01625209594650

  • The potential energy when separation is r is

\\U(r)=U(r)-U(\infty)\\=\frac{q_1q_2}{4 \pi \epsilon_0r}1625209594829

Relation Between Electric Field and Electric Potential:

If we know the electric potential in a region we can find the electric field

dV=-Edr cos\theta1625209594985

where,

θ is the angle between E and dr

Electric Potential Due to a Dipole:

i) at axial point

V_{axial}=\frac{kP}{\left ( r^{2}-l^{2} \right )}1625209595289

if r>>l

V_{axi}=\frac{1}{4\pi \epsilon _{0}}\frac{P}{r^{2}}1625209595439

ii) at equatorial point:

V_{equi}= 01625209595588

iii) General point

V_{g}=\frac{1}{4\pi \epsilon _{0}}\frac{P\cos \Theta }{r^{2}}1625209595739

Work done in rotation of dipole and equilibrium of dipole:

W=PE\left ( \cos \Theta _{1} -\cos \Theta _{2}\right )1625209595901

W=PE\left ( \cos \Theta _{1} -\cos \Theta _{2}\right )1625209596056

\\if \ \theta_1=90 \ and \ \theta_2=\theta\\W=-PEcos\theta=-P.E1625209596203

This work done is stored as potential energy.

Condition for the stable equilibrium of a dipole:

  1. Angle (θ): The system is stable when the angle between the dipole moment (p) and the electric field (E) is 0° (aligned).

  2. Torque: In this position, the net torque acting on the dipole is zero. Any slight deviation from this position causes a restoring torque, bringing the dipole back into alignment with the field.

  3. Potential Energy: When the dipole is aligned with the electric field, its potential energy is at its lowest.

Condition for the unstable equilibrium of a dipole:

  1. Angle (θ): The system is in unstable equilibrium when the angle between p and E is 180° (anti-aligned).

  2. Torque: In this position, the net torque acting on the dipole is zero. Any small displacement from this position, however, produces a torque that increases the angle between p and E, pushing the dipole out of alignment.

  3. Potential Energy: The dipole's potential energy is greatest when it is anti-aligned with the electric field.

Electrostatics of Conductors

  • At electrostatic equilibrium, the electric field inside a charged conductor is zero.
  • The electric field at every point on the surface of a charged conductor is normal (perpendicular) to the surface.
  • In a static situation, the excess charge on a charged conductor exists only on its surface.
  • There is no electric field inside the cavity of a conductor, providing electrostatic shielding.
  • At electrostatic equilibrium, the electrostatic potential remains constant throughout the conductor.

Dielectrics and Polarization

  • Dielectrics are non-conducting materials, and they do not have free charge carriers that can move easily within the material.

Non-Polar Molecules:

The centres of negative and positive charges coincide in a non-polar molecule. The non-polar molecule lacks a permanent dipole moment.

Example: O2, H2

Polar Molecule:

Polar molecules have negative and positive charge centres that are separated and have a permanent dipole moment.

Example: H2O, HCl

NOTE :

Both polar and non-polar dielectrics acquire a net dipole moment in the presence of an external electric field.

Polarization:

It is the dipole moment per unit volume

\small \\P=\chi_eE\\ \chi_e \text{ is the electric susceptibility of the dielectric medium}1625209596354

  • Polarized dielectrics are similar to two charge surfaces with an induced charge density of opposite polarity.

Capacitor

A capacitor is a system of two conductors, which are separated by an insulator. A capacitor is used to store a large amount of charge.

The charge stored in a capacitor:

\small Q=CV1625209596499

where, C is capacitance and V is voltage

Capacitance (C):

The capacitance of a capacitor

\small C=Q/V1625209596643

Dielectric Strength:

Dielectric strength is the maximum amount of electric field that a dielectric medium can withstand.

Parallel Plate Capacitor:

Two conducting plates of area A separated by a distance d. If the dielectric medium between the capacitor plate is vacuum or air, then

\small C=\frac{\epsilon_0 A}{d}1625209596795

16252096236061625209596942

  • When a dielectric of dielectric constant k is inserted between the above capacitor, the new capacitance

\small \\C'=\frac{k\epsilon_0 A}{d}\\C'=kC1625209597095

Combination of capacitors:

  • For n capacitors connected in parallel, the net value of capacitance is

\small C=C_1+C_2+C_3+.........C_n1625209597244

  • For n capacitors connected in series, the net value of capacitance is

\small \frac{1}{C}=\frac{1}{C_1}+\frac{1}{C_2}+\frac{1}{C_3}+..............\frac{1}{C_n}1625209597394

Energy Stored in a Capacitor:

The energy U stored in a capacitor of capacitance C, charge Q and voltage V is

\small U=\frac{1}{2}CV^21625209597551

The electric energy density

In a region with an electric field, the electric energy density,

\small \text{Energy per unit volume}=\frac{1}{2}\epsilon_0E^21625209597717

A Van de Graaff Generator:

A Van de Graaff Generator:

Van de Graaff generator is used for accelerating charged particles. It consists of a large spherical conducting shell. The charge is continuously transferred to the shell with the help of a moving belt and brushes. The potential of million volts rebuilt up and can be used for accelerating the charged particles.

.

16252096248081625209597885

Significance of NCERT Class 12 Physics Chapter 2 Notes

Electrostatic potential and capacitance Class 12 notes will be helpful to revise the chapter and to get an idea about the main topics covered in the chapter. Also, this NCERT class 12 physics chapter 2 notes are useful to cover the main topics of the class 12 CBSE physics syllabus and also for competitive exams like VITEEE, BITSAT, JEE Main, NEET etc. Class 12 physics chapter 2 notes pdf download can be used to prepare in offline mode.

Key Features of NCERT CBSE Class 12 Physics ch 2 Notes

  • Comprehensive coverage of key topics from Chapter 2 - Electrostatic Potential and Capacitance.
  • Electrostatic Potential and Capacitance class 12 notes are written in clear and concise language, making complex concepts simple to grasp.
  • Physics class 12 chapter 2 notes pdf concentrate on developing a solid conceptual foundation in electrostatic potential and capacitance.
  • Class 12 Physics chapter 2 notes are easily downloadable in PDF format, allowing for offline learning.
  • CBSE class 12 physics ch 2 notes designed to help with exam preparation for board and competitive exams such as JEE and NEET.

NCERT Class 12 Notes Chapterwise

Subject Wise NCERT Exampler solutions

Subject Wise NCERT Solutions

NCERT Books and Syllabus

Frequently Asked Questions (FAQs)

1. What are the main derivations covered in the electrostatic potential and capacitance Class 12 notes?

No derivations are covered in the NCERT notes for Class 12 Physics chapter 2. This NCERT note is a brief of the main topics and equations covered in the chapter and can be used for revising the electrostatic potential and capacitance.

2. What are the main derivations of the NCERT Class 12 Physics chapter 2?

The main derivations covered in the NCERT Book are potential due to dipoles, potential due to a point charge, the potential energy of dipole in an external field, etc.

3. How important is the chapter for the CBSE board exam?

Electrostatic Potential and Capacitance" is an important chapter for CBSE Class 12 Physics board exams, providing a conceptual foundation as well as practical applications in everyday life, with exam questions frequently appearing. Students should thoroughly understand the concepts in order to score well.

4. What is the energy stored in the capacitor in terms of charge and voltage?

 U=0.5QV

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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