Class 9 Physics Chapter 1 Electric Charges and Fields MCQ with Answers (30 Questions)

The rationalized CBSE syllabus (2024-25) has significantly increased objective-type questions in Class 9 assessments. MCQs now account for 25–35% of total marks in many schools' periodic tests and board exams. This shift reflects two key trends: (1) Time efficiency—MCQs allow examiners to test breadth of knowledge across multiple concepts in short duration, and (2) Conceptual rigour—well-designed MCQs eliminate rote memorization and demand critical thinking. In Electric Charges and Fields, MCQs often test whether students can distinguish between scalar and vector quantities (charge vs. electric field), apply Coulomb's law numerically, visualize field lines, understand dipole behaviour under external fields, and interpret Gauss's law across different scenarios. Single-answer MCQs test factual recall; assertion-reason MCQs test deeper understanding of cause-effect relationships. Mastering both formats is essential for scoring ≥8/10 in this chapter. The questions below mirror actual CBSE exam patterns and include trap options designed to catch common misconceptions.

**Q1.** Electric charge is a ____ quantity. (A) scalar (B) vector (C) tensor (D) derived **Answer: (A) scalar** — Charge has magnitude only, no direction; addition follows algebraic rules, not vector rules. **Q2.** The SI unit of electric charge is: (A) Ampere (B) Coulomb (C) Joule (D) Newton **Answer: (B) Coulomb** — Coulomb (C) is the standard SI unit; 1 C = charge flowing in 1 second at 1 Ampere. **Q3.** Two identical charges repel each other with force F. If the distance between them is halved, the new force is: (A) F/4 (B) F/2 (C) 2F (D) 4F **Answer: (D) 4F** — Coulomb's law: F ∝ 1/r²; halving r increases force by (1/0.5)² = 4 times. **Q4.** The electric field due to a point charge is ____ at the location of the charge itself. (A) zero (B) infinite (C) finite and positive (D) undefined **Answer: (D) undefined** — E = kq/r²; at r = 0, the expression is undefined; field strength cannot be measured at the source. **Q5.** An electric dipole consists of: (A) two unlike charges very close together (B) two like charges very far apart (C) a single positive charge (D) a conductor in isolation **Answer: (A) two unlike charges very close together** — A dipole has charges +q and –q separated by a small distance; the dipole moment is p = q × d. **Q6.** The electric field inside a conductor in electrostatic equilibrium is: (A) zero (B) maximum (C) equal to field outside (D) inversely proportional to charge **Answer: (A) zero** — In equilibrium, free charges redistribute on the surface, creating zero net field inside. **Q7.** Gauss's law relates electric flux to: (A) charge enclosed (B) distance from charge (C) area of surface (D) permeability of space **Answer: (A) charge enclosed** — Φ = q_enclosed/ε₀; flux through any closed surface depends only on enclosed charge. **Q8.** The electric field is defined as: (A) force per unit charge (B) potential per unit distance (C) charge per unit force (D) energy per unit distance **Answer: (A) force per unit charge** — E = F/q; it represents the force experienced by a unit positive test charge. **Q9.** Two charges +2 C and –2 C are separated by 1 m. The system is: (A) a monopole (B) a dipole (C) a quadrupole (D) neutral only **Answer: (B) a dipole** — Opposite charges close together form a dipole with dipole moment p = 2 × 1 = 2 C·m. **Q10.** Electric field lines: (A) can intersect (B) form closed loops (C) begin on positive charges and end on negative charges (D) carry current **Answer: (C) begin on positive charges and end on negative charges** — Field lines are a visual convention; they never intersect (field has unique direction at each point) and are perpendicular to conductor surfaces.

**Q11.** A charge q₁ = +3 μC is at origin, and q₂ = +2 μC is at distance 2 m. The electric field at the midpoint (1 m from each) due to q₁ is: (A) 2.7 × 10⁴ N/C towards q₂ (B) 2.7 × 10⁴ N/C towards q₁ (C) 6.75 × 10⁴ N/C away from q₁ (D) 1.35 × 10⁴ N/C away from q₁ **Answer: (A) 2.7 × 10⁴ N/C towards q₂** — E₁ = k × 3 × 10⁻⁶ / 1² = 9 × 10⁹ × 3 × 10⁻⁶ = 2.7 × 10⁴ N/C; since q₁ is positive, field points away from q₁ (towards q₂). **Q12.** Two charges experience Coulomb force F when separated by r. If both charges are tripled and distance is doubled, the force becomes: (A) 9F/4 (B) 9F (C) F/4 (D) 27F/8 **Answer: (A) 9F/4** — F' = k(3q₁)(3q₂)/(2r)² = 9kq₁q₂/4r² = (9/4) × F. **Q13.** A test charge of +1 μC is placed at a point where electric field is 5 N/C. The force on the test charge is: (A) 5 N (B) 5 × 10⁻⁶ N (C) 5 μN (D) 5 × 10⁶ N **Answer: (B) 5 × 10⁻⁶ N** — F = qE = 1 × 10⁻⁶ × 5 = 5 × 10⁻⁶ N (or 5 μN); forces on microcoulomb charges are tiny. **Q14.** The electric dipole moment of a pair of opposite charges ±q separated by distance d is: (A) qd (B) q/d (C) q²d (D) d/q **Answer: (A) qd** — Dipole moment p = q × d, a vector pointing from negative to positive charge; SI unit is C·m. **Q15.** An electric dipole is placed in a uniform electric field E. The net force on the dipole is: (A) pE (B) qE (C) zero (D) p/E **Answer: (C) zero** — Equal and opposite forces act on ±q charges; net force = qE – qE = 0 (but torque ≠ 0). **Q16.** The torque on a dipole in a uniform field E is maximum when the dipole makes an angle θ with E: (A) θ = 0° (B) θ = 45° (C) θ = 90° (D) θ = 180° **Answer: (C) θ = 90°** — τ = pE sin θ; maximum when sin θ = 1, i.e., θ = 90° (dipole perpendicular to field). **Q17.** Gauss's law in its integral form is: (A) Φ = q_enc / ε₀ (B) E = q / (4πε₀r²) (C) F = kq₁q₂ / r² (D) p = qd **Answer: (A) Φ = q_enc / ε₀** — This is Gauss's law; Φ is total electric flux through closed surface; works for any charge distribution. **Q18.** A uniform spherical charge distribution has total charge Q and radius R. Using Gauss's law, the field at distance r > R is: (A) kQ/r² (B) kQ/R² (C) kQr/R³ (D) zero **Answer: (A) kQ/r²** — Outside a uniform sphere, field is same as if all charge Q were at centre; E = kQ/r². **Q19.** An electric field line makes an angle of 30° with the normal to a surface. For a field element dA perpendicular to the surface, the electric flux is: (A) E × dA (B) E × dA × cos 30° (C) E × dA × sin 30° (D) E × dA / cos 30° **Answer: (B) E × dA × cos 30°** — Flux dΦ = E · dA = E × dA × cos θ, where θ is angle between E and normal (here 30°). **Q20.** A spherical Gaussian surface of radius r encloses a point charge q. The electric field at the surface is E. If radius is doubled to 2r, the new field is: (A) E (B) E/4 (C) E/2 (D) 2E **Answer: (B) E/4** — For point charge, E ∝ 1/r²; if r → 2r, then E_new = E/(2²) = E/4.

**Q21.** **Assertion (A):** Electric field inside a uniformly charged conducting sphere is zero. **Reason (R):** All free charges in a conductor move to the surface in electrostatic equilibrium. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is false (C) A is false, R is true (D) Both A and R are false **Answer: (A) A is true, R is true; R is correct explanation of A** — In equilibrium, charge distributes on surface only; inside E = 0 throughout (even for non-uniform internal charge density). **Q22.** **Assertion (A):** Coulomb's law is valid only for point charges. **Reason (R):** Extended charge distributions can be treated as assemblies of point charges. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (B) A is true, R is true; R is not correct explanation** — Coulomb's law is fundamentally stated for point charges; extended distributions require integration, but the law itself does not change—we use superposition. **Q23.** **Assertion (A):** Electric field lines never form closed loops. **Reason (R):** Electric field is conservative, so work done around a closed loop is zero. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — Conservative field → potential is single-valued → field lines cannot loop; closed loops would imply non-zero circulation and non-conservative nature. **Q24.** **Assertion (A):** A conductor in electrostatic equilibrium has electric field **E = 0** inside. **Reason (R):** Electric potential is constant throughout the conductor. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — If E = 0 inside, then dV/dr = 0 everywhere inside, so V is constant (equipotential); conversely, constant V → E = 0. **Q25.** **Assertion (A):** Electric flux through a closed Gaussian surface is independent of its shape. **Reason (R):** Gauss's law depends only on enclosed charge, not on surface shape or external charge distribution. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — Φ = q_enc/ε₀ is independent of shape; any closed surface enclosing same q_enc gives same flux. **Q26.** **Assertion (A):** An electric dipole placed in a uniform external field experiences a net force. **Reason (R):** The two charges of the dipole experience opposite forces. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (C) A is false, R is true** — Opposite forces cancel (net F = 0), but they create a torque; A is wrong even though R is correct. **Q27.** **Assertion (A):** Gauss's law can be applied to any closed surface, even non-spherical ones. **Reason (R):** The law is derived assuming spherical symmetry of charge distribution. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (B) A is true, R is true; R is not correct explanation** — Gauss's law is general (true for any surface); though often derived for spheres, it applies universally by divergence theorem. **Q28.** **Assertion (A):** The electric field due to an infinite uniformly charged plane is E = σ/(2ε₀), independent of distance from the plane. **Reason (R):** By symmetry, field must be perpendicular to the plane, and Gauss's law applied to a cylindrical surface yields this result. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — Infinite plane → uniform field perpendicular to surface; Gaussian cylinder with area A encloses charge σA, giving E = σ/(2ε₀) on each side. **Q29.** **Assertion (A):** Two like charges always repel each other. **Reason (R):** Coulomb's law states F = k|q₁q₂|/r², and this force is always repulsive for like charges. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — Like charges have same sign; Coulomb's law with proper vector form shows repulsion; opposite charges attract. **Q30.** **Assertion (A):** The electric field at the surface of a conductor is perpendicular to the surface. **Reason (R):** If field had a tangential component, charges would move along the surface, violating electrostatic equilibrium. (A) A is true, R is true; R is correct explanation of A (B) A is true, R is true; R is not correct explanation (C) A is false, R is true (D) Both are false **Answer: (A) A is true, R is true; R is correct explanation of A** — At equilibrium, E_tangential = 0 (else charges flow); E is purely normal, confirming equipotential surface.

**Trap 1: Confusing 'charge is a scalar' with 'field is a scalar'.** Many students select vector for charge because they hear 'charges repel in different directions'. Remember: charge is a scalar (just magnitude); the **force or field** is a vector. Example: Q1 tests this—charge is scalar, field is vector. **Trap 2: Forgetting the 1/r² relationship in Coulomb's law.** Students often choose proportionality like 1/r or 1/r³. Always recall: F ∝ 1/r² (inverse square law). Doubling distance quarters force; halving distance quadruples it. Q3 and Q20 test this directly. **Trap 3: Assuming net force on a dipole in uniform field is non-zero.** Because the two charges are separate, students think total force ≠ 0. Reality: +q and –q experience equal-magnitude forces in opposite directions → they cancel. Torque ≠ 0, but **net translational force = 0**. Q15 targets this misconception. **Trap 4: Mixing up 'field at a point' with 'field due to a charge'.** The field at the exact location of a point source is undefined (not zero, not infinite—it's mathematically undefined). Many exams give option 'infinite' as a trap. Q4 clarifies this. **Trap 5: Thinking Gauss's law depends on surface shape or external charges.** Gauss's law: Φ = q_enc/ε₀ depends **only** on enclosed charge. Shape and external charges don't matter. Q17 and Q26 test this core principle. **Trap 6: Equating electric flux with electric field.** Flux is the product of field and area (times cosine of angle). They are NOT the same. Field is intensity; flux is a measure of 'lines passing through' a surface. Q19 tests this distinction. **Trap 7: Misinterpreting assertion-reason questions.** Both A and R can be individually true, but R might not explain A. Example: Q22 has both true, but R doesn't explain why A is limited to point charges. Read carefully: does R logically support A? **Trap 8: Forgetting units in numerical problems.** Q13 uses μC, which becomes 10⁻⁶ C. Forgetting the conversion leads to wrong magnitude by factor of 10⁶. Always convert to SI before calculating.

**Step 1: Categorize Before You Start (1–2 minutes).** Quickly scan all MCQ questions and mentally label them: Easy (basic recall), Medium (one-step calculation), Hard (multi-step or assertion-reason). This prevents you from spending 5 minutes on an Easy question. **Step 2: Tackle Easy First (0.5 min per question).** Questions 1–10 in this quiz should take ~5 minutes total. These build confidence and lock in guaranteed marks. Examples: Q1 (scalar), Q2 (SI unit), Q6 (field inside conductor). Do not second-guess these; mark and move. **Step 3: Medium Questions Next (1–1.5 min per question).** Questions 11–20 require short calculations (Coulomb's law substitution, flux formula, dipole properties). Allocate ~15–20 minutes. Write down the formula, plug in numbers, eliminate wrong units. Example: Q11 is a field calculation—write E = kq/r², substitute, check direction. **Step 4: Hard/Assertion-Reason Last (1.5–2 min per question).** Questions 21–30 demand conceptual depth. Spend the last 10–15 minutes here. Read both A and R; ask: *Is A correct? Is R correct? Does R explain A?* If in doubt between (A) and (B), re-read the reason carefully. Example: Q22 has A and R both true, but they aren't linked—so (B) is correct, not (A). **Step 5: Review & Guess Strategy (3–5 minutes).** If you're unsure of a Medium or Hard question, use elimination: rule out obviously wrong options (e.g., if units don't match, eliminate). Never leave blanks in CBSE MCQ—there's no negative marking in most schools. For assertion-reason, when stuck, *A is false, R is true* is a common trap; default to (A) if both seem true unless you're confident R doesn't support A. **Step 6: Post-Exam Check (if time allows).** If you finish early, review Hard questions only—not Easy, which you're confident about. Recompute Medium calculations if uncertain. Spend zero time re-reading Easy questions. **Sample Timing Breakdown (30 MCQs in 45 minutes, as per typical CBSE exam):** - Scan & categorize: 2 min - Easy (Q1–Q10): 5 min - Medium (Q11–Q20): 18 min - Hard (Q21–Q30): 15 min - Review: 5 min Practise this rhythm with this quiz. Consistency beats speed; accuracy beats rushing. Start a 3-day free trial at cbsetutor.ai to access interactive MCQ timers, instant feedback, and video explanations for every question.

The new CBSE Class 9 syllabus emphasizes understanding over rote learning. In Electric Charges and Fields, examiners use MCQs to probe whether students truly grasp fundamental concepts or are merely regurgitating formulas. **Example distinction:** A student who memorizes 'F = kq₁q₂/r²' might still fail Q3 (about halving distance) if they don't understand that force depends on r⁻². A student who reasons 'field is force per unit charge' will confidently answer Q8 without looking at memorized definitions. **Three conceptual pillars to master:** 1. **Charge as a fundamental scalar property.** Understand why charge doesn't have direction, how it combines algebraically, and how it differs from force or field. This ensures correct answers in Q1, Q2, Q14. 2. **Field as a local property of space.** The field E at any point represents the force a unit positive charge would experience there. It's not 'attached' to the source charge but is a property of space itself. This clarity prevents confusion in Q4, Q8, Q18. 3. **Gauss's law as a restatement of Coulomb.** Don't memorize Gauss's law in isolation. Understand that Φ = q_enc/ε₀ is a consequence of Coulomb's law for **any** closed surface; it's a powerful tool for high-symmetry distributions (planes, spheres, cylinders). This insight unlocks Q17, Q27, Q28. Students who reason 'What does each formula mean? When does it apply? What are its limits?' consistently outperform memorizers on CBSE assessments. Use this quiz not as a test, but as a diagnostic tool: if you answer a question 'correctly' but cannot explain why the other options are wrong, revisit the concept before moving on.