Class 12 physics Ch 2
Electrostatic Potential and Capacitance Class 12 Notes Chapter 2
Electrostatic Potential and Capacitance Class 12 Notes
Class 12 physics chapter
Chapter 2
Class 12 physics chapter
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Electrostatic Potential and Capacitance Class 12 Notes Chapter 2
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Chapter 2 Results
NCERT Results for Class 12 physics Chapter 2 – Free PDF Download
NCERT Results for Class 12 physics Chapter 2 Results provides accurate and acceptable physics knowledge. The NCERT Results for Class 12 physics can be utilised by the scholars to prepare for the first term examination and to break the exercise questions of the Class 12 physics Chapter 2. All the results are created according to the rearmost term – I CBSE Syllabus for 2021-22 and its guidelines.
These NCERT Results for Class 12 physics help scholars to clear all their doubts related to this chapter with ease. Further, scholars might also use this resource for preparing notes and performing variations. Click the link given below to download the NCERT Results for Class 12 physics Chapter 2 PDF for free.
1. Electrostatic Potential The electrostatic potential at any point in an electric field is equal to the amount of work done per unit positive test charge or in bringing the unit positive test charge from infinite to that point, against the electrostatic force without acceleration.
NOTE: Electrostatic potential is a state dependent function as electrostatic forces are conservative forces.
2. Electrostatic Potential Difference The electrostatic potential difference between two points in an electric field is defined as the amount of work done in moving a unit positive test charge from one point to the other point against of electrostatic force without any acceleration (i.e. the difference of electrostatic potentials of the two points in the electric field).
where, is work done in taking charge q0 from A to B against of electrostatic force.
Also, the line integral of electric field from initial position A to final position B along any path is termed as potential difference between two points in an electric field, i.e.
NOTE: As, work done on a test charge by the electrostatic field due to any given charge configuration is independent of the path, hence potential difference is also same for any path.
For the diagram given as below, potential difference between points A and B will be same for any path.
3. Electrostatic potential due to a point charge q at any point P lying at a distance r from it is given by
4. The potential at a point due to a positive charge is positive while due to negative charge, it is negative.
5. When a positive charge is placed in an electric field, it experiences a force which drives it from points of higher potential to the points of lower potential. On the other hand, a negative charge experiences a force driving it from lower potential to higher.
6. Electrostatic potential due to an electric dipole at any point P whose position vector is r w.r.t. mid-point of dipole is given by
7. The electrostatic potential on the perpendicular bisector due to an electric dipole is zero.
8. Electrostatic potential at any point P due to a system of n point charges q1, q2, ……………, qn whose position vectors are r1,r2,…,rn respectively, is given by
where, r is the position vector of point P w.r.t. the origin.
9. Electrostatic potential due to a thin charged spherical shell carrying charge q and radius R respectively, at any point P lying
10. Graphical representation of variation of electric potential due to a charged shell at a distance r from centre of shell is given as below:
11 Equipotential Surface A surface which have same electrostatic potential at every point on it, is known as equipotential surface.
The shape of equipotential surface due to
(i) line charge is cylindrical.
(ii) point charge is spherical as shown along side:
(a) Equipotential surfaces do not intersect each other as it gives two directions of electric field E at intersecting point which is not possible.
(b) Equipotential surfaces are closely spaced in the region of strong electric field and vice-versa.
(c) Electric field is always normal to equipotential surface at every point of it and directed from one equipotential surface at higher potential to the equipotential surface at lower potential.
(d) Work done in moving a test charge from one point of equipotential surface to other is zero.
12. Relationship between electric field and potential gradient
where, negative sign indicates that the direction of electric field is from higher potential to lower potential, i.e. in the direction of decreasing potential.
NOTE: (i) Electric field is in the direction of which the potential decreases steepest.
(ii) Its magnitude is given by the change in the magnitude of potential per unit displacement normal to the equipotential surface at the point.
13. Electrostatic Potential Energy The work done against electrostatic force gets stored as potential energy. This is called electrostatic potential
What is the ratio of electric field intensity at a point on the equatorial line to the field at a point on axial line when the points are at the same distance from the centre of the dipole?
For an isolated parallel plate capacitor of capacitance C and potential difference V, what will happen to (i) charge on the plates (ii) potential difference across the plates (iii) field between the plates (iv) energy stored in the capacitor, when the distance between the plates is increased? [Answer: (i) No change (ii) increases (iii) No change (iv) increases].
A storage capacitor on a RAM (Random Access Memory) chip has a capacity of 55pF. If the capacitor is charged to 5.3V, how may excess electrons are on its negative plate?[Answer: 1.8 × 10^9]
The potential at a point A is –500V and that at another point B is +500V. What is the work done by external agent to take 2 units (S.I.) of negative charge from B to A.
In charging a capacitor of capacitance C by a source of emf V, energy supplied by the sources QV and the energy stored in the capacitor is ½QV. Justify the difference.
A point charge Q is kept at the intersection of (i) face diagonals (ii) diagonals of a cube of side a. What is the electric flux linked with the cube in (i) & (ii)?
Using Gauss’s theorem in electrostatics, deduce an expression for electric field intensity due to a charged spherical shell at a point (i) inside (ii) on its surface (iii) outside it. Graphically show the variation of electric field intensity with distance from the centre of shell.
Important Questions
A conducting slab of thickness ‘t’ is introduced between the plates of a parallel plate capacitor, separated by a distance d (t<d). Derive an expression for the capacitance of the capacitor. What will be its capacitance when t = d?
A potential difference V is applied across a conductor of length L and diameter D. How are the electric field E and the resistance R of the conductor affected when (i) V is halved (ii) L is halved (iii) D is doubled.
Justify your answer.
What is an equipotential surface? Write three properties Sketch equipotential surfaces of (i) Isolated point charge (ii) Uniform electric field (iii) Dipole
NOTE: Electrostatic potential is a state dependent function as electrostatic forces are conservative forces.
2. Electrostatic Potential Difference The electrostatic potential difference between two points in an electric field is defined as the amount of work done in moving a unit positive test charge from one point to the other point against of electrostatic force without any acceleration (i.e. the difference of electrostatic potentials of the two points in the electric field).
where, is work done in taking charge q0 from A to B against of electrostatic force.
Also, the line integral of electric field from initial position A to final position B along any path is termed as potential difference between two points in an electric field, i.e.
NOTE: As, work done on a test charge by the electrostatic field due to any given charge configuration is independent of the path, hence potential difference is also same for any path.
For the diagram given as below, potential difference between points A and B will be same for any path.
3. Electrostatic potential due to a point charge q at any point P lying at a distance r from it is given by
4. The potential at a point due to a positive charge is positive while due to negative charge, it is negative.
5. When a positive charge is placed in an electric field, it experiences a force which drives it from points of higher potential to the points of lower potential. On the other hand, a negative charge experiences a force driving it from lower potential to higher.
6. Electrostatic potential due to an electric dipole at any point P whose position vector is r w.r.t. mid-point of dipole is given by
7. The electrostatic potential on the perpendicular bisector due to an electric dipole is zero.
8. Electrostatic potential at any point P due to a system of n point charges q1, q2, ……………, qn whose position vectors are r1,r2,…,rn respectively, is given by
where, r is the position vector of point P w.r.t. the origin.
9. Electrostatic potential due to a thin charged spherical shell carrying charge q and radius R respectively, at any point P lying
10. Graphical representation of variation of electric potential due to a charged shell at a distance r from centre of shell is given as below:
11 Equipotential Surface A surface which have same electrostatic potential at every point on it, is known as equipotential surface.
The shape of equipotential surface due to
(i) line charge is cylindrical.
(ii) point charge is spherical as shown along side:
(a) Equipotential surfaces do not intersect each other as it gives two directions of electric field E at intersecting point which is not possible.
(b) Equipotential surfaces are closely spaced in the region of strong electric field and vice-versa.
(c) Electric field is always normal to equipotential surface at every point of it and directed from one equipotential surface at higher potential to the equipotential surface at lower potential.
(d) Work done in moving a test charge from one point of equipotential surface to other is zero.
12. Relationship between electric field and potential gradient
where, negative sign indicates that the direction of electric field is from higher potential to lower potential, i.e. in the direction of decreasing potential.
NOTE: (i) Electric field is in the direction of which the potential decreases steepest.
(ii) Its magnitude is given by the change in the magnitude of potential per unit displacement normal to the equipotential surface at the point.
13. Electrostatic Potential Energy The work done against electrostatic force gets stored as potential energy. This is called electrostatic potential
What is the ratio of electric field intensity at a point on the equatorial line to the field at a point on axial line when the points are at the same distance from the centre of the dipole?
For an isolated parallel plate capacitor of capacitance C and potential difference V, what will happen to (i) charge on the plates (ii) potential difference across the plates (iii) field between the plates (iv) energy stored in the capacitor, when the distance between the plates is increased? [Answer: (i) No change (ii) increases (iii) No change (iv) increases].
A storage capacitor on a RAM (Random Access Memory) chip has a capacity of 55pF. If the capacitor is charged to 5.3V, how may excess electrons are on its negative plate?[Answer: 1.8 × 10^9]
The potential at a point A is –500V and that at another point B is +500V. What is the work done by external agent to take 2 units (S.I.) of negative charge from B to A.
In charging a capacitor of capacitance C by a source of emf V, energy supplied by the sources QV and the energy stored in the capacitor is ½QV. Justify the difference.
A point charge Q is kept at the intersection of (i) face diagonals (ii) diagonals of a cube of side a. What is the electric flux linked with the cube in (i) & (ii)?
Using Gauss’s theorem in electrostatics, deduce an expression for electric field intensity due to a charged spherical shell at a point (i) inside (ii) on its surface (iii) outside it. Graphically show the variation of electric field intensity with distance from the centre of shell.
Important Questions
A conducting slab of thickness ‘t’ is introduced between the plates of a parallel plate capacitor, separated by a distance d (t<d). Derive an expression for the capacitance of the capacitor. What will be its capacitance when t = d?
A potential difference V is applied across a conductor of length L and diameter D. How are the electric field E and the resistance R of the conductor affected when (i) V is halved (ii) L is halved (iii) D is doubled.
Justify your answer.
What is an equipotential surface? Write three properties Sketch equipotential surfaces of (i) Isolated point charge (ii) Uniform electric field (iii) Dipole
The physics syllabus of Class 12 covers several different chapters making it a complicated subject to attend. NCERT has results for all the chapters of Class 12, which aims at enhancing the conception of scholars. It also suggests a different approach to the content covered in Chapter 2 and helps scholars to break questions rightly using a logical methodology. physics Class 12 NCERT results Chapter 2 helps to prepare scholars to understand the question pattern for board examinations.
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