These NCERT Solutions for Class 12 Physics Chapter 1 Electric Charges and Fields cover all 24 back-exercises and 9 solved examples for the 2026-27 syllabus, with full step-by-step working. The chapter carries 5 to 7 marks in CBSE boards.
Here is what this chapter is worth across the main exams:
- CBSE Weightage: 5 to 7 marks, usually one short answer plus one numerical.
- JEE Main: 3 to 4 percent, on field, flux, and dipole moment.
- NEET: one to two questions a year on Coulomb's force and field due to point charges.
Exercise-by-Exercise Breakdown for Class 12 Physics Chapter 1
The 24 solved NCERT questions on this page split into the groups below. Use it to plan which answers to practise first.
| Question group | Questions solved | Typical CBSE marks |
|---|---|---|
| Coulomb's force (point charges, medium) | 5 | 3 to 5 |
| Electric field and field lines | 5 | 2 to 3 |
| Electric flux and Gauss's law | 6 | 3 to 5 |
| Electric dipole (field, torque, energy) | 4 | 3 to 5 |
| Charge, quantisation and mixed numericals | 4 | 1 to 3 |
Coulomb's Law.
Electric Charges and Fields Previous Year Questions and Weightage
Chapter 1 averages about 6 marks in CBSE. The table maps its CBSE, JEE Main, and NEET appearances over six sessions.
| Year | CBSE Board | JEE Main | NEET |
|---|---|---|---|
| 2026 | Gauss's law derivation (3 marks) | Dipole field on axial line (4 marks) | Coulomb's law and Gauss's law (electric field, dipole) |
| 2025 | Coulomb force on three point charges (5 marks) | Electric flux through closed surface (4 marks) | Field due to dipole (4 marks) |
| 2024 | Electric field of an infinite sheet (3 marks) | Force between two charges in medium (4 marks) | Quantisation of charge MCQ |
| 2023 | Dipole in uniform external field (5 marks) | Linear charge density on a wire (4 marks) | Coulomb's law SI unit MCQ |
| 2022 | Gauss's law applied to a charged shell (3 marks) | Superposition of three charges (4 marks) | Electric field lines property |
| 2021 | - | Force on a dipole in non-uniform field | Field due to point charge |
How to Write Board Answers for Electric Charges and Fields
Getting the number right is only half the marks. The way you set out each answer earns the rest. Follow these steps when you write any Chapter 1 answer in the exam.
- Draw the charge or field diagram first. Mark every charge with its sign and show the field or force arrows. Examiners give a separate mark for a labelled diagram.
- Write the formula in vector form, then resolve into components. For two or three charges, split each force into x and y parts before adding, so you never add vectors as plain numbers.
- Pick the correct Gaussian surface and say why. Sphere for a point charge or shell, cylinder for a wire, pillbox for a sheet. State the symmetry argument, it is marked on its own.
- Keep the working symbolic until the last line. Substitute numbers only at the final step, then state the SI unit on every quantity.
- End with a clear final-answer line. Box the magnitude, the unit, and the direction (repulsive, attractive, or along a named axis).
Answer-Writing Mistakes That Cost Marks in Chapter 1
These are the slips students make while writing or calculating the answer in the exam, not gaps in concept. Each one costs 1 to 3 marks.
Mistake 1: Adding forces or fields as plain numbers. They are vectors, so resolve into components and add direction by direction before combining.
Mistake 2: Choosing the wrong Gaussian surface, or skipping the symmetry line. The surface must match the charge geometry, and the reason must be written out.
Mistake 3: Dropping or mixing SI units mid-working, then losing the unit mark on the final answer. Carry the unit on every line.
Mistake 4: Substituting numbers too early. Premature numeric substitution hides slips and makes the algebra marks hard to award; stay symbolic till the last step.
See also: Chapter 1 Formula Sheet with derivations
Other Electric Charges and Fields Class 12 Resources
| Resource | Link |
|---|---|
| NCERT Solutions | You are here |
| Notes | Chapter 1 Notes |
| Handwritten Notes | Chapter 1 Handwritten Notes |
| Formula Sheet | Chapter 1 Formula Sheet |
| NCERT Book PDF | Chapter 1 Book PDF |
Electric field.
NCERT Solutions for Class 12 Physics: All Chapters
Jump to any other chapter below.
| Chapter | Resource |
|---|---|
| Chapter 2 | Electrostatic Potential and Capacitance |
| Chapter 3 | Current Electricity |
| Chapter 4 | Moving Charges and Magnetism |
| Chapter 5 | Magnetism and Matter |
| Chapter 6 | Electromagnetic Induction |
| Chapter 7 | Alternating Current |
| Chapter 8 | Electromagnetic Waves |
| Chapter 9 | Ray Optics and Optical Instruments |
| Chapter 10 | Wave Optics |
| Chapter 11 | Dual Nature of Radiation and Matter |
| Chapter 12 | Atoms |
| Chapter 13 | Nuclei |
| Chapter 14 | Semiconductor Electronics |
Electric Charges and Fields Class 12 Video Lecture
Source: NCERT Wallah on YouTube
All NCERT Solutions for Class 12 Physics Chapter 1 Electric Charges and Fields with Step-by-Step Solutions
Each NCERT Class 12 Physics Electric Charges and Fields question is listed below. Click Detailed Solution to open its full step-by-step solution, the expert method, and an alternate approach on the question page.
What is the force between two small charged spheres having charges of 2 × 10-7 C and 3 × 10-7 C placed 30 cm apart in air?
The electrostatic force on a small sphere of charge 0.4 µC due to another small sphere of charge -0.8 µC in air is 0.2 N.
(a) What is the distance between the two spheres?
(b) What is the force on the second sphere due to the first?
Check that the ratio k e2G me mp is dimensionless. Look up a Table of Physical Constants and determine the value of this ratio. What does the ratio signify?
(a) Explain the meaning of the statement 'electric charge of a body is quantised'.
(b) Why can one ignore quantisation of electric charge when dealing with macroscopic (large-scale) charges?
When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.
Four point charges qA = 2 µC, qB = -5 µC, qC = 2 µC, qD = -5 µC are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of 1 µC placed at the centre of the square?
(a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
(b) Explain why two field lines never cross each other at any point.
Two point charges qA = 3 µC and qB = -3 µC are located 20 cm apart in vacuum.
(a) What is the electric field at the midpoint O of the line AB joining the two charges?
(b) If a negative test charge of magnitude 1.5 × 10-9 C is placed at this point, what is the force experienced by the test charge?
A system has two charges qA = 2.5 × 10-7 C and qB = -2.5 × 10-7 C located at points A:(0, 0, -15 cm) and B:(0, 0, +15 cm), respectively. What are the (a) total charge and (b) electric dipole moment of the system?
An electric dipole with dipole moment 4 × 10-9 C m is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 104 N C-1. Calculate the magnitude of the torque acting on the dipole.
A polythene piece rubbed with wool is found to have a negative charge of 3 × 10-7 C.
(a) Estimate the number of electrons transferred (from which to which?).
(b) Is there a transfer of mass from wool to polythene?
(a) Two insulated charged copper spheres A and B have their centres separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is 6.5 × 10-7 C? The radii of A and B are negligible compared to the distance of separation.
(b) What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?
Suppose the spheres A and B in Exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?
Figure 1.33 shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge-to-mass ratio?
Consider a uniform electric field E = 3 × 103 î N/C.
(a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the yz-plane?
(b) What is the flux through the same square if the normal to its plane makes a 60° angle with the x-axis?
What is the net flux of the uniform electric field of Exercise 1.15 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes?
Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is 8.0 × 103 N m2/C.
(a) What is the net charge inside the box?
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or why not?
A point charge +10 µC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)
A point charge of 2.0 µC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
A point charge causes an electric flux of -1.0 × 103 N m2/C to pass through a spherical Gaussian surface of 10.0 cm radius centred on the charge.
(a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?
(b) What is the value of the point charge?
A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 103 N/C and points radially inward, what is the net charge on the sphere?
A uniformly charged conducting sphere of 2.4 m diameter has a surface charge density of 80.0 µC/m2.
(a) Find the charge on the sphere.
(b) What is the total electric flux leaving the surface of the sphere?
An infinite line charge produces a field of 9 × 104 N/C at a distance of 2 cm. Calculate the linear charge density.
Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17.0 × 10-22 C/m2. What is E: (a) in the outer region of the first plate, (b) in the outer region of the second plate, and (c) between the plates?
NCERT Solutions Class 12 Physics Ch 1 Electric Charges and Fields FAQs
Ques. How many questions are solved on this NCERT Solutions page?
Ans. This page solves all 24 NCERT back-exercise questions of Class 12 Physics Chapter 1, grouped into Coulomb's force, electric field, flux and Gauss's law, dipole, and mixed charge numericals. Each answer has a step-by-step Solution and an Expert Solution in collapsible tabs.
Ques. What is Coulomb's law in Class 12 Physics Chapter 1?
Ans. Coulomb's law says the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance, along the line joining them. The solutions derive it in vector form and apply it to two and three-charge setups.
Ques. How should I write the Gauss's law derivation in the board exam?
Ans. Start by stating Gauss's law, then draw the Gaussian surface that matches the symmetry (cylinder for a wire, pillbox for a sheet, sphere for a shell) and justify the choice. Take E out of the integral, evaluate the flux, equate it to the enclosed charge over epsilon-naught, and solve for E. State the SI unit on the final line. The worked answers on this page follow exactly this order.
Ques. What is the weightage of Chapter 1 in the CBSE board exam?
Ans. It carries 5 to 7 marks in CBSE, usually one short answer plus one numerical or derivation. JEE Main adds 3 to 4 percent and NEET draws one to two questions a year.
Ques. How do I present a Coulomb's law numerical for full marks?
Ans. Draw the charges with their signs, write Coulomb's law in vector form, and resolve each force into components for three-charge setups. Keep the algebra symbolic, substitute numbers only at the end, and finish with the magnitude, SI unit, and direction. The solved answers on this page show this layout step by step.
Comments