Potential Energy of a System of Charge: Definition, Formula, Solutions & Class 12 Notes

Physics Electrostatic Potential and Capacitance 2025

Vikash Kumar Vishwakarma
Updated on Aug 8, 2025 10:02 IST

By Vikash Kumar Vishwakarma

In a space or system, there could be multiple electrical charges. The energy that's stored may not be equal, but could be relative. Today we will explain an interesting section of your Electrostatic Potential and Capacitance chapter in Physics, about the potential energy of a system of charges. The basic idea here is to learn how the distance between two electrical charges along with the magnitude and medium permittivity influence potential energy. These principles tell us how capacitors behave, how energy is conserved, and how charge is configured in such multiple charge systems.

 

 

Table of content
  • Define Potential Energy of a System of Charges
  • Potential Energy of Two Point Charges
  • Potential Energy of Multiple Charges
  • Notes for Class 12 Physics
  • Class 12 Physics NCERT Solutions
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Define Potential Energy of a System of Charges

The total work done by external forces to bring charges from infinity to their current position without any acceleration is referred to as the potential energy of a system of charges. This concept helps to understand the interactions and stability of charged systems.

Important Links:

NCERT Class 12 Notes
CBSE Class 12 Maths NCERT notes
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Potential Energy of Two Point Charges

If we are looking into the mathematical description, there is just one key aspect to know. Work done. The amount of work done for two charges separated at infinity to be brought somewhere closer is the potential energy of two point charges.

 

We will use this general formula.

U = 1 4 π ε 0 · q 1 q 2 r

What are these variables?

  •  U is the electrostatic potential charge
  • R is the distance between two charges
  • q 1 q_1  and q 2 q_2
  • ε 0 \varepsilon_0

Signs of U: When Charges Attract and Repel

  • Positive potential energy (U > 0): When both charges are like charges, that tells us they are repelling each other
  • Negative potential energy (U < 0): If the electrical charges have opposite signs, they are attracting each other.

 

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Potential Energy of Multiple Charges

The amount of work done to gather all charges from infinity to their current position without acceleration is expressed as the potential energy of multiple charges.

General Formula

System of n point charges q1,q2,q3,,qn​ placed at a distance of r i j from each other.

The potential energy U is: U = i < j 1 4 π ε 0 · q i q j r i j

Where,

  • U is potential energy.
  • q i and q j are two charges in the system.
  • r i j is the distance between the charges
  • ε0​ is the permittivity of free space.

Also Check:

NCERT Class 12 notes
Class 12 Maths NCERT notes
Physics Electrostatic Potential and Capacitance Logo

Notes for Class 12 Physics

Sl. No

Name of Chapter

1

Chapter 1: Electric Charges and Fields

2

Chapter 2: Electrostatic Potential and Capacitance

3

Chapter 3: Current Electricity

4

Chapter 4: Moving Charges and Magnetism

5

Chapter 5: Magnetism and Matter

6

Chapter 6: Electromagnetic Induction

7

Chapter 7: Alternating Current

8

Chapter 8: Electromagnetic Waves

9

Chapter 9: Ray Optics and Optical Instruments

10

Chapter 10: Wave Optics

11

Chapter 11: Dual Nature of Radiation and Matter

12

Chapter 12: Atoms

13

Chapter 13: Nuclei

14

Chapter 14: Semiconductor Electronics: Materials, Devices and Simple Circuits

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Physics Electrostatic Potential and Capacitance Exam

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