# CBSE Class 12 Physics Revision Notes Chapter 2

## Class 12 Physics Chapter 2 Notes – Electrostatic Potential and Capacitance

Physics is a crucial subject for all those students who want to major in engineering or other science-oriented streams. Class 12 Physics Chapter 2 is about Electrostatic Potential and Capacitance.

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## Key Topics Covered In Class 12 Physics Chapter 2 Notes

The Class 12 Physics Chapter 2 Notes prepared by experienced faculty at Extramarks will help you score good grades by helping you to revise quickly with sample papers, exercise solutions,and end-text questions. . All the essential concepts are explained in easy language. You just can’t say no to these notes which are customised as per the students needs and requirement.Be a smart decision maker to select the right study material to boost your performance and stay ahead of the pact.

The key topics covered under NCERT Solutions Class 12 Physics Chapter 2 Notes are:

### Electric Charge:

Class 12 Physics Chapter 2 Notes mainly focus on electric charge and its properties. Electric charge is a phenomenon where any matter experiences a force when placed in an electromagnetic field. The SI Unit of electric charge is Coulomb. It is denoted by “C”.

### Coulomb’s Law:

Whenever two charges of opposite signs are kept near, they experience a force called attraction. Similarly, if two charges of similar signs are kept near, they experience a force called repulsion.

Coulomb’s law illustrates the force happening between charges in mathematical form.

According to Coulomb’s law, the force of attraction or force of repulsion between two charged bodies is proportional directly to the product of the charges and inversely proportional to the square of the distance between two charged bodies.

If F is the force between two charged bodies, ‘q1’ and ‘q2’, which are kept at a distance ‘r’ between them,  then the force can be defined as:

F ∝ q1 q2/ r2

F = k ( q1 q2/ r2 ). Where k is the constant of proportionality.

Coulomb’s Law is an important topic to find out the extent of attraction and repulsion force between two particles, having some charge and students can refer to our Class 12 Physics Chapter 2 Notes to get a thorough understanding of the topic.

### Electric Field:

It is a field that surrounds any charged particle. It exerts an attractive or repulsive force on other charged particles.  We have covered this  topic briefly. Students are recommended to register on Extramarks’ website to  access  Class 12 Physics Chapter 2 Notes.

#### Properties of the electric field:

• It is denoted by E.
• In a charge-free region, electric field lines are continuous and smooth
• Two electric field lines never intersect or cross each other.
• The electric field is measured in SI units of V/m ( Volts per metre).
• The direction of the electric field is radially outwards for a positively charged particle.
• Its direction is radially inwards for negatively charged particles.

### Electric Potential Energy:

As explained in our Class 12 Physics Chapter 2 Notes, the amount of work required to move one unit of charge from one point to another against an electric field is called electric potential energy.

#### Electric Potential:

It is the energy an external force takes to bring a charge from infinity to a particular point.

The charge ‘q’ moves away from R through a repulsive force of charge ‘Q’. An external force is required to bring back the charge ‘q’ from ‘R’ to ‘P’, opposite to the repulsive force.

Hence, External force = -(Repulsive force)

Work done on charges RP = RPF ext dr = -RPFE dr

If the point R be a charge at infinity, and ‘d’ be the distance between charges P & R,

Then work is done on charges W = -∞dFE dr

Now, the total work done in bringing chare from ∞ to distance ‘d’, will be as follows:

W =   -∞d 14??0 q qor2dr

W = 14??0 q qor2

But, V = W/q0

V = 14??0 q r

• The above equation holds for charges with any signs.
•  The unit to measure electric potential is Volts. And hence it is often called voltage.
• Mathematically, one volt/V of electric potential means 1 joule /J of energy spend per 1 Column / C of charge.

1 V =1  J/C

### Electric Dipole:

It is defined as a couple of charges with opposite signs (q and -q) separated by a distance d. The direction of an electric dipole is always from negative charge to positive charge.

The electric dipole can be visualised in the following manner:

As explained in our Class 12 Physics Chapter 2 Notes there are two opposite charges, Q and -Q, separated by a distance of d. This creates an electric dipole between the two.

#### Properties of an electric dipole:

• An electric dipole is denoted by ‘p’.
• It is a vector quantity.
• The line along the direction of an electric dipole is the axis of the dipole.

The electric potential due to a dipole is given as,

V = 14?? p cos?r2

Case 1

If the value of ? =90,

Then V =0

Case 2

If the value of ? = 0,

Then V = 14?? pr2

### Gauss law:

According to Gauss Law, the electric flux out of any enclosed surface equals the charge divided by the permittivity.

• The electric flux of any area is the electric field multiplied by the surface area.
• Electric flux is perpendicular to the field in consideration.

According to gauss law,

1. ds = 1?oq

To enhance your  understanding of the Gauss law with real life applications and scenarios, students are recommended to refer to our Class 12 Physics Chapter 2 Notes.

### Capacitors:

A capacitor is a system where an insulator separates two conductors. If the conductors have a potential difference between them, then they can be used to accelerate the charges. With this acceleration, the system develops the capability to store energy. Hence, a device that stores energy by keeping charges, and maintaining a potential difference between conductors, is called a capacitor.

Further as explained in our Class 12 Physics Chapter 2 Notes, two conductors/plates have opposite charges, Q and -Q. Due to the opposite charges present, it creates a potential difference between the two. Both the conductive plates, A and B, are separated at a distance d. The area between two conductive plates is filled with a dielectric material having permittivity as ?.

#### Capacitance:

The capacitance for a capacitor is defined as C = Q/V. C or capacitance is the amount of charge required to raise the potential of the conductor by 1 volt.

#### Parallel Plate Capacitor:

A parallel plate capacitor includes two thin conducting plates of area A, separated at a distance ‘d’. If a positive charge is given to one plate, then a negative charge gets inducted to the second plate and a positive charge on the outer part of the second plate. As the face of the second plate is connected to the ground, a negative charge is left on this plate.

The arrangement of a parallel plate capacitor can be illustrated as follows:

The electric field between these two plates can be defined as,

E = ?2 ?o + ?2 ?o

E = ? ?o

If a uniform potential difference is present between plates, then electric charge E is as follows:

V = Ed

V = ?d ?o

V = qd?oA

C = qV

These are further in-depth  explanations given in our Class 12 Physics Chapter 2 Notes. Once these are appropriately studied, students can check out the solutions and exercises for practice.

### Van De Graaff Generator:

It is a generator used to build up voltages in a million volts. Hence, the electric field accelerates the charged particles like protons, electrons, and ions. These charged particles are then used for conducting experiments or examining the small-scale structure of matter.

### Construction and Working:

In a Van De Graaff Generator, an insulating column holds the sizable spherical shell located from the ground. The  two pulleys are bound to the belt around the shell and column. They  are situated at the ground and top positions. The belt continuously moves, and hence a positive charge is transferred to the giant shell by carbon brush, which further renders the outer shell with very high potential energy. The belt moves due to the driving done by the motor on the blower pulley.

#### Uses of Van De Graaff Generator:

• Used to generate a high potential voltage.
• Used to study nuclear Physics.

#### Here’s a quick summary of Class 12 Physics Chapter 2 Notes:

•  The electrostatic potential is a scalar quantity representing a region around the charge used to calculate the work.
• involved when a charge moves around other charges.
• Potential is a scalar quantity.
• Potential can be positive, negative or zero.
• The SI unit of potential is volts/V or Joule per Coulomb, i.e. J/C.
• The potential increases when we go away from the negative charge and decreases when we go away from the positive charge.
• A capacitor is an appliance used to store energy.
• To store a large amount of energy without increasing the size of the capacitor, maximum plates are used.
• Capacitance is measured in Farads or F.
• The capacitance of the earth is approximately 711 µF.

## Class 12 Physics Chapter 2 Notes: Exercises &  Solutions

Class 12 Physics Chapter 2 Notes is all about electrostatic potential and capacitance. In the electricity  chapter, the production of energy was learnt. But how that energy gets stored and applied to different products is explained in this Chapter.

Class 12 Physics Chapter 2 Notes is divided into sixteen subtopics, covering all the electrostatic potential and capacitance sections. Students can click on the  links given below   to know all the solutions to problems included in NCERT textbooks. The below links contain detailed solutions to all critical questions from NCERT books, Previous Year Question Papers, and Sample Papers.

Students can refer to the respective exercise to access the NCERT solutions Class 12 Physics Chapter 2. Students can also explore a repository of educational materials as per their requirement to speed up their preparation by registering  on the Extramarks’ website. Click on the links given below:

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### Key Features of NCERT Solutions Class 12 Physics Chapter 2 Notes

While studying from NCERT textbooks might not be sufficient for students to understand the concept thoroughly. Hence Extramarks has introduced the series of Notes of Class 12 Physics Chapter 2, designed to help students with detailed authentic solutions to solve those complex and tricky questions. Solving these exercises and practice questions will also prepare them well for assignments, tests, exams as well as other competitive examinations such as NEET, JEE Main, Advanced, etc. Students need not worry about any other assistance from teachers or parents. Extramarks provides one-stop solution to all your problems.

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• All the CBSE Revision Notes and CBSE Class 12 Physics Chapter 2 Notes are exclusively prepared for students by subject matter experts at Extramarks.
•  Every and every topic in the chapter is thoroughly explained with examples and illustrations. All the Notes are written in simple and easy language.
• Students can refer to notes, solutions, question papers, or any study material through the Extramarks’ website. Students need to register themselves to access these study materials.
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### 1. Is it essential to refer to CBSE Class 12 Physics Chapter 2 Notes?

Students should be attentive in their class lectures and It’s equally important to go through NCERT books first. Then studying from Class 12 Physics Chapter 2 Notes will definitely help students understand the topic better, and getting a clear understanding of the subject means getting good grades in the exams.

### 2. Which are the best Revision Notes recommended for Class 12 Physics Chapter 2 Notes?

On the internet, there is a plethora of study materials. However, they are also the greatest distraction and you might lose more of your valuable time. Be a smart decision maker and select the right study material to step up your preparation and stick to it. . Regular studies and revisions from Extramarks resources will definitely boost your performance. Extramarks notes are prepared by subject matter experts who strictly adhere to CBSE guidelines. The notes are easy to understand, and  students can practice a lot of questions and stick to a study schedule and follow it religiously to come out with flying colors. No wonder millions of students swear by Extramarks because of the authenticity and trust it has built over the years.

### 3. What are real-time applications of Class 12 Physics Chapter 2?

Class 12 Physics Chapter 2 is about electrostatic potential and capacitance. A lot of new technologies use the concept of electrostatic potential and capacitors. We can find the application of electrostatics in Van De Graaff Generator or photocopy machines, laser printers, and inkjet printers. Other examples include electrostatic air cleaning equipment and processes, smoke precipitators, electrostatic painting, etc.