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Class 12 Physics Chapter 1 Important Questions for Board Exam 2026 (With Answers)

Chapter 1: Electric Charges and Fields – Important Questions

🔹 Very Short Answer Questions (1 Mark)

Q1. What is the SI unit of electric charge? Answer: The SI unit of electric charge is coulomb (C). Q2. Is electric charge a scalar or vector quantity? Answer: Electric charge is a scalar quantity. Q3. What is the charge of an electron? Answer: The charge of an electron is −1.6 × 10⁻¹⁹ C.

🔹 Short Answer Questions (2 Marks)

Q4. State Coulomb’s law. Answer: Coulomb’s law states that the force of attraction or repulsion between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. Q5. What is meant by quantisation of charge? Answer: Electric charge exists in discrete packets and is always an integral multiple of e (1.6 × 10⁻¹⁹ C). This property is called quantisation of charge.

🔹 Short Answer Questions (3 Marks)

Q6. Define electric field and write its SI unit. Answer: Electric field at a point is defined as the force experienced by a unit positive test charge placed at that point. SI unit of electric field is N/C. Q7. Write any three properties of electric field lines. Answer:
  1. Electric field lines start from positive charges and end on negative charges.
  2. No two electric field lines intersect each other.
  3. The density of field lines represents the strength of the electric field.

🔹 Long Answer Questions (5 Marks)

Q8. Derive an expression for the electric field due to a point charge. Answer: Consider a point charge q placed in free space. Let P be a point at distance r from the charge. According to Coulomb’s law, the force experienced by a test charge q₀ placed at P is: F = (1 / 4πε₀) × (q q₀ / r²) Electric field E = F / q₀ So, E = (1 / 4πε₀) × (q / r²) This is the expression for electric field due to a point charge.
Q9. Explain Gauss’s law. Write its mathematical form. Answer: Gauss’s law states that the total electric flux through any closed surface is equal to 1/ε₀ times the total charge enclosed within the surface. Mathematical form: Φ = ∮ E · dS = q / ε₀

🔹 Important Numericals for Practice

Q10. Calculate the force between two charges of 2 μC and 3 μC placed 10 cm apart in air. (Numerical – frequently asked in exams)

🔹 FAQs

Q1. Which chapter is most important in Class 12 Physics? Electric Charges and Fields is very important as it forms the base of electrostatics. Q2. Are numericals important for Physics board exams? Yes, numericals carry significant marks and are asked every year. Q3. Is NCERT enough for Class 12 Physics? NCERT is essential, but practicing important questions improves confidence and marks.
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