Tamil Nadu 12th Physics Unit 1 Electrostatics Important Questions, Numericals, Derivations and Preparation Tips
Unit 1 Electrostatics is the first and one of the most important chapters in Tamil Nadu 12th Physics. This page lists 14 important 2 mark, 7 important 3 mark and 6 important 5 mark questions, plus numerical problems, derivations, a preparation plan. Focus on the derivations (torque on a dipole, potential, Gauss's law applications, capacitors) and the Van de Graaff generator, and practise them with diagrams.
Harmanpreet Kaur28 Sept, 2026
Electrostatics is the first unit of Tamil Nadu 12th Physics and a high-scoring chapter in the board exam. This page lists 27 important questions from the unit: 14 two mark, 7 three mark and 6 five mark questions. It also covers numerical problems, the derivations to revise, a preparation plan, and FAQs. You can download the Electrostatics important questions PDF for practice. Follow the latest Tamil Nadu HSC 12th 2027 notification for board updates, and check the Tamil Nadu HSE 2nd year time table 2027 to plan your revision around the exam dates.
Tamil Nadu HSE+2 Electrostatic Overview
The table below gives a quick snapshot of Unit 1 and the resources on this page.
| Particulars | Details |
| Board | Directorate of Government Examinations (DGE), Tamil Nadu |
| Class | 12th (HSC / +2) |
| Subject | Physics |
| Unit | Unit 1: Electrostatics |
| Important 2 Mark Questions | 14 |
| Important 3 Mark Questions | 7 |
| Important 5 Mark Questions | 6 |
| Theory Marks (Physics) | 70 |
| Exam Duration | 3 hours |
12th Physics Unit 1 Electrostatics Important Questions
The important questions in this unit fall into three groups. Two mark questions are definitions and short notes, three mark questions are mostly short derivations, and five mark questions are long derivations with diagrams. The table below shows the question count for each group so you can plan your revision.
| Question Type | Marks | Number of Questions | What to Expect |
| Very short answer | 2 | 14 | Definitions, laws, short notes, and comparisons |
| Short answer | 3 | 7 | Derivations of torque, potential, capacitance, and energy |
| Long answer | 5 | 6 | Electric field derivations and the Van de Graaff generator |
Electrostatics Important 2 Mark Questions
These questions test your grasp of basic definitions and laws. Write the statement, the formula, and the SI unit in each answer to secure full marks.
| S.No. | Important 2 Mark Question |
| 1 | What is meant by quantization of charges? |
| 2 | Write down Coulomb's law in vector form and mention what each term represents. |
| 3 | What are the differences between Coulomb force and gravitational force? |
| 4 | Write a short note on the superposition principle. |
| 5 | Define 'electric field'. |
| 6 | The electric field lines never intersect. Justify. |
| 7 | Define 'electric dipole'. Give the expression for the magnitude of its electric dipole moment and its direction. |
| 8 | Define 'electrostatic potential'. What is an equipotential surface? |
| 9 | Define 'electric flux'. |
| 10 | Write a short note on 'electrostatic shielding'. |
| 11 | What is polarization? |
| 12 | What is dielectric strength? |
| 13 | Define 'capacitance'. Give its unit. |
| 14 | What is corona discharge? |
Electrostatics Important 3 Mark Questions
The 3 mark questions are mainly derivations. Write the given data, draw a neat diagram, show each step, and end with the final expression.
| S.No. | Important 3 Mark Question |
| 1 | Derive an expression for the torque experienced by a dipole due to a uniform electric field. |
| 2 | Derive an expression for electrostatic potential due to a point charge. |
| 3 | Derive an expression for electrostatic potential energy of the dipole in a uniform electric field. |
| 4 | Obtain Gauss's law from Coulomb's law. |
| 5 | Obtain the expression for capacitance of a parallel plate capacitor. |
| 6 | Obtain the expression for energy stored in the parallel plate capacitor. |
| 7 | Derive the expression for resultant capacitance when capacitors are connected in series and in parallel. |
Electrostatics Important 5 Mark Questions
Five mark questions are long derivations and one application-based explanation. Draw a clear diagram, define every symbol, apply Gauss's law or superposition where needed, and write the final result clearly.
| S.No. | Important 5 Mark Question |
| 1 | Calculate the electric field due to a dipole on its axial line and equatorial plane. |
| 2 | Derive an expression for electrostatic potential due to an electric dipole. |
| 3 | Obtain the expression for electric field due to an infinitely long charged wire. |
| 4 | Obtain the expression for electric field due to a charged infinite plane sheet. |
| 5 | Obtain the expression for electric field due to a uniformly charged spherical shell. |
| 6 | Explain in detail the construction and working of a Van de Graaff generator. |
Electrostatics Important Numerical Problems
Numericals in this unit are formula-based and quick to score once you practise. The table gives sample problems with answers so you can check your working. Write the formula, substitute with units, and state the final answer with its unit.
| S.No. | Numerical Problem | Answer |
| 1 | Two point charges of 3 µC and 5 µC are placed 0.5 m apart in air. Find the force between them. | 0.54 N |
| 2 | Find the electric field at 0.3 m from a point charge of 5 µC. | 5 × 10⁵ N/C |
| 3 | Find the potential at 2 m from a point charge of 4 µC. | 1.8 × 10⁴ V |
| 4 | A dipole has charges ±2 µC separated by 4 cm. Find its dipole moment. Find the torque when it is placed at 30° to a field of 5 × 10⁴ N/C. | p = 8 × 10⁻⁸ C m; τ = 2 × 10⁻³ N m |
| 5 | Capacitors of 2 µF, 3 µF and 6 µF are connected in series. Find the effective capacitance. | 1 µF |
| 6 | The same three capacitors are connected in parallel. Find the effective capacitance. | 11 µF |
| 7 | A 10 µF capacitor is charged to 100 V. Find the energy stored. | 0.05 J |
Electrostatics Important Derivations
Derivations make up all of the 3 mark and most of the 5 mark questions in this unit, so learn them step by step. The table lists every derivation with its marks and the main concept it relies on.
| S.No. | Derivation | Marks | Key Concept Used |
| 1 | Torque on a dipole in a uniform electric field | 3 | Force couple and perpendicular distance |
| 2 | Electrostatic potential due to a point charge | 3 | Work done in moving a unit charge |
| 3 | Potential energy of a dipole in a uniform electric field | 3 | Work done in rotating the dipole |
| 4 | Gauss's law from Coulomb's law | 3 | Electric flux through a closed surface |
| 5 | Capacitance of a parallel plate capacitor | 3 | Field between plates and V = Ed |
| 6 | Energy stored in a parallel plate capacitor | 3 | Work done in charging the capacitor |
| 7 | Series and parallel combination of capacitors | 3 | Charge and potential relations |
| 8 | Electric field of a dipole on the axial line and equatorial plane | 5 | Superposition principle and small dipole approximation |
| 9 | Electrostatic potential due to an electric dipole | 5 | Superposition of potentials |
| 10 | Electric field due to an infinitely long charged wire | 5 | Gauss's law with a cylindrical surface |
| 11 | Electric field due to a charged infinite plane sheet | 5 | Gauss's law with a Gaussian pillbox |
| 12 | Electric field due to a uniformly charged spherical shell | 5 | Gauss's law with a spherical surface |
How to Prepare Unit 1 Electrostatics for the 12th Physics Exam?
Electrostatics rewards steady practice, since the same formulae and derivations repeat across questions. Follow these steps.
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Read the textbook chapter first. Understand the basics before memorising formulae. Check the Tamil Nadu HSC syllabus to confirm the topics.
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Learn the 2 mark questions first. These are short definitions and notes that are quick to revise and easy to score.
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Make a formula sheet. Write Coulomb's law, electric field, potential, dipole moment, torque, and capacitor formulae with their units.
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Practise derivations with diagrams. Draw each figure and write every step until you can do it without notes.
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Solve numericals daily. Try a few problems from each type, including capacitor combinations.
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Attempt model papers and past papers. Solve the Tamil Nadu 12th Physics model papers and previous year question papers in timed conditions.
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Know the paper format. Read the Tamil Nadu Class 12 exam pattern to plan your time across the parts.
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Plan around the exam dates. Use the Tamil Nadu HSE 2nd year time table 2027 to set a revision schedule, and keep an eye on the Tamil Nadu HSC 12th 2027 notification for any official updates.
Tamil Nadu 12th Physics Unit 1 Electrostatics Important Questions, FAQs
1. What are the most important questions in Tamil Nadu 12th Physics Unit 1 Electrostatics?
2. Which derivations should I learn in Electrostatics for the 12th Physics exam?
3. Which 5 mark questions are important in Electrostatics?
4. How can I score full marks in Electrostatics numericals?
5. How should I revise Electrostatics important questions before the board exam?
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