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# Electrostatic Potential and Capacitance Class 12 Notes Physics

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## Electrostatic Potential and Capacitance Class 12 Notes

Download CBSE class 12th revision notes for chapter 2 Electrostatic Potential and Capacitance in PDF format for free. Download revision notes for Electrostatic Potential and Capacitance class 12 Notes and score high in exams. These are the Electrostatic Potential and Capacitance class 12 Notes prepared by team of expert teachers. The revision notes help you revise the whole chapter 2 in minutes. Revision notes in exam days is one of the best tips recommended by teachers during exam days.

## CBSE Class 12 Physics Revision Notes Chapter 2 Electrostatic Potential and Capacitance

Electrostatic Potential at a Point: It is the work done by per unit charge by an external agency, in bringing a charge from infinity to that point.

• Electrostatic Potential due to a Charge at a Point
$V(r)=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Q}{r}$
• The electrostatic potential at a point with position vector r due to a point dipole of dipole moment p place at the origin
$V(r)=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{\overrightarrow{p}.\overrightarrow{r}}{{{r}^{2}}}$
The result is true also for a dipole (with charges –q and q separated by 2a) for r >> a.
• For a charge configuration q1, q2, …… qn with position vectors r1, r2, ….rn, the potential at a point P is given by the superposition principle, where r1p is the distance between q1 and P, as and so on.
• Electrostatics Potential Energy Stored in a System of Charges: It is the work done (by an external agency) in assembling the charges at their locations.
• Electrostatic Potential Energy of Two Charges q1, q2, at r1, r2:
• $U=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{1}}{{q}_{2}}}{{{r}_{12}}}$ where r12 is distance between q1 and q2
• Potential Energy of a Charge q in an External Potential: V(r)=qV(r)
• Potential Energy of a Dipole of Dipole Moment p in a Uniform Electric Field: E = –p.E.
• Equipotential Surface: An equipotential surface is a surface over which potential has a constant value.
1. For a point charge, concentric spheres centered at a location of the charge are equipotential surfaces.
2. The electric field E at a point is perpendicular to the equipotential surface through the point.
3. E is in the direction of the steepest decrease of potential.
• Capacitance C of a System of Two Conductors Separated by an Insulator: It is defined as, $C=\frac{Q}{V}$ where Q and – Q are the charges on the two conductors V is the potential difference between them.
• Capacitance is determined purely geometrically, by the shapes, sizes, and relative positions of the two conductors.
• Capacitance C of a parallel plate capacitor (with the vacuum between the plates): $C={{\varepsilon }_{0}}\frac{A}{d}$ where A is the area of each plate and d the separation between them.
• For capacitors in the series combination: The total capacitance C is $\frac{1}{C}=\frac{1}{{{C}_{1}}}+\frac{1}{{{C}_{2}}}+\frac{1}{{{C}_{3}}}+....$
• For capacitors in the parallel combination: The total capacitance C is $C={{C}_{1}}+{{C}_{2}}+{{C}_{3}}+......$ where ${C_1},{\text{ }}{C_2},{\text{ }}{C_3}...$ are individual capacitances.
• The energy U stored in a capacitor of capacitance C, with charge Q and voltage V: $U=\frac{1}{2}QV=\frac{1}{2}C{{V}^{2}}=\frac{1}{2}\frac{{{Q}^{2}}}{C}$
• The electric energy density (energy per unit volume) in a region with electric field: $(1/2){{\varepsilon }_{0}}{{E}^{2}}$
• The potential difference between the conductor (radius ro) inside & outside spherical shell (radius R): $\phi ({{r}_{0}})-\phi (R)=\frac{q}{4\pi {{\varepsilon }_{0}}}\left(\frac{1}{{{r}_{0}}}-\frac{1}{R} \right)$ which is always positive.
• When the medium between the plates of a capacitor filled with an insulating substance: Changes observed are as follows: Polarization of the medium gives rise to a field in the opposite direction.
1. The net electric field inside the insulating medium is reduced.
2. Potential difference between the plates is thus reduced.
3. Capacitance C increases from its value when there is no medium (vacuum). where K is the dielectric constant of the insulating substance.
• Electrostatic Shielding: A conductor has a cavity with no charge inside the cavity, then no matter what happens outside the conductor. Even if there are intense electric fields outside the conductor, the cavity inside has, shielding whatever is inside the cavity from whatever is outside the cavity. This is called electrostatic shielding.

## CBSE Class 12 Revision Notes and Key Points

Electrostatic Potential and Capacitance class 12 Notes. CBSE quick revision note for class-12 Physics, Chemistry, Maths, Biology, and other subject are very helpful to revise the whole syllabus during exam days. The revision notes covers all important formulas and concepts given in the chapter. Even if you wish to have an overview of a chapter, quick revision notes are here to do if for you. These notes will certainly save your time during stressful exam days.

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