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Current Electricity Class 12 MCQs 2026-27 | CBSE Physics Chapter 3
Current Electricity Class 12 Physics — MCQs with Answers
Practise these original CBSE-style multiple-choice questions for Class 12 Physics Chapter 3, Current Electricity. The set covers the current 2026–27 syllabus and mixes direct concepts, calculations, graphs, circuit reasoning and competency-style situations.
Important: These are original practice MCQs, not official CBSE questions and not claimed PYQs. CBSE's official 2026–27 curriculum lists Current Electricity as Chapter 3 under Unit II, with 17 marks assigned to the unit as a whole; it does not publish a fixed Chapter-3-only mark allocation. The current CBSE Class XII SQP/MS page is also available for understanding the broader paper format.
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1. Current Electricity MCQs — Core Concepts
Q1. Electric current through a conductor is defined as:
A. Charge flowing per unit length
B. Charge flowing per unit time
C. Energy flowing per unit time
D. Potential difference per unit charge
Answer: B
Current is the rate of flow of charge: I = dQ/dt.
Current is the rate of flow of charge: I = dQ/dt.
Q2. In a metallic conductor, conventional current is in the direction:
A. Opposite to electron drift
B. Same as electron drift
C. Perpendicular to electron drift
D. Randomly related to electron drift
Answer: A
Electrons are negatively charged, so their drift is opposite to conventional current.
Electrons are negatively charged, so their drift is opposite to conventional current.
Q3. The SI unit of current density is:
A. A m
B. A/m
C. A/m²
D. C/m
Answer: C
J = I/A, so the SI unit is A m−2.
J = I/A, so the SI unit is A m−2.
Q4. For a conductor carrying current I through cross-sectional area A, current density is:
A. IA
B. I/A
C. A/I
D. I + A
Answer: B
Current density is current per unit cross-sectional area.
Current density is current per unit cross-sectional area.
Q5. In the simple microscopic model of a metal, drift speed of electrons is proportional to:
A. 1/E
B. E
C. E² only
D. Zero for every E
Answer: B
For the model used in the chapter, vd = eEτ/m, so vd is proportional to E when τ is fixed.
For the model used in the chapter, vd = eEτ/m, so vd is proportional to E when τ is fixed.
Q6. Mobility of a charge carrier is defined as:
A. E/vd
B. vd/E
C. I/E
D. E/I
Answer: B
μ = vd/E.
μ = vd/E.
Q7. The current in a metallic conductor is related to drift velocity by:
A. I = neAvd
B. I = ne/(Avd)
C. I = nA/(evd)
D. I = e/(nAvd)
Answer: A
The microscopic current relation is I = neAvd.
The microscopic current relation is I = neAvd.
Q8. The SI unit of resistivity is:
A. Ω
B. Ω m
C. Ω/m
D. S/m
Answer: B
From R = ρL/A, resistivity has SI unit Ω m.
From R = ρL/A, resistivity has SI unit Ω m.
Q9. Conductivity σ is related to resistivity ρ by:
A. σ = ρ
B. σ = ρ²
C. σ = 1/ρ
D. σ = 1/ρ²
Answer: C
Conductivity is the reciprocal of resistivity.
Conductivity is the reciprocal of resistivity.
Q10. For a uniform wire, resistance is given by:
A. R = ρA/L
B. R = ρL/A
C. R = L/(ρA)
D. R = A/(ρL)
Answer: B
Resistance increases with length and decreases with cross-sectional area.
Resistance increases with length and decreases with cross-sectional area.
Q11. If the length of a uniform wire is doubled while its area and resistivity remain unchanged, its resistance becomes:
A. R/2
B. R
C. 2R
D. 4R
Answer: C
Since R ∝ L, doubling L doubles R.
Since R ∝ L, doubling L doubles R.
Q12. A V–I graph for an ohmic conductor at constant temperature is:
A. A straight line through the origin
B. A circle
C. A parabola necessarily
D. A horizontal line
Answer: A
Ohm's law gives V = IR, so V is directly proportional to I.
Ohm's law gives V = IR, so V is directly proportional to I.
Q13. On a V versus I graph for an ohmic resistor, the slope represents:
A. Conductance
B. Resistance
C. Resistivity
D. Current density
Answer: B
slope = ΔV/ΔI = R.
slope = ΔV/ΔI = R.
Q14. On an I versus V graph for an ohmic resistor, the slope represents:
A. Resistance
B. Resistivity
C. Conductance
D. Power
Answer: C
slope = ΔI/ΔV = 1/R = G.
slope = ΔI/ΔV = 1/R = G.
Q15. Which statement about Ohm's law is correct?
A. It applies to every electrical device under all conditions.
B. It states that V is proportional to I when relevant physical conditions are kept constant.
C. It says resistance is always independent of temperature.
D. It applies only to semiconductors.
Answer: B
Ohm's law is conditional on the relevant physical conditions remaining constant.
Ohm's law is conditional on the relevant physical conditions remaining constant.
Q16. For a typical metallic conductor over a suitable temperature range, resistance generally:
A. Decreases with temperature
B. Increases with temperature
C. Remains exactly zero
D. Becomes independent of material
Answer: B
For typical metals, resistance increases approximately linearly with temperature over a limited range.
For typical metals, resistance increases approximately linearly with temperature over a limited range.
Q17. Electrical power consumed by a resistor can be written as:
A. VI only
B. I²R only
C. V²/R only
D. All of these, for an ohmic resistor
Answer: D
P = VI = I²R = V²/R.
P = VI = I²R = V²/R.
Q18. One kilowatt-hour is equal to:
A. 3.6 × 10³ J
B. 3.6 × 10⁴ J
C. 3.6 × 10⁵ J
D. 3.6 × 10⁶ J
Answer: D
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J.
1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J.
Q19. A real cell of emf ε and internal resistance r supplies current I. Its terminal voltage is:
A. ε + Ir
B. ε − Ir
C. Ir − ε
D. εrI
Answer: B
When the cell is delivering current, V = ε − Ir.
When the cell is delivering current, V = ε − Ir.
Q20. When a cell is being charged, the terminal potential difference is represented by:
A. ε − Ir
B. ε + Ir
C. ε/I
D. Ir/ε
Answer: B
For charging current, the terminal voltage is greater than the emf under the usual sign convention: V = ε + Ir.
For charging current, the terminal voltage is greater than the emf under the usual sign convention: V = ε + Ir.
2. Application and Numerical MCQs
Q21. A current of 3 A flows for 4 minutes. The charge passing through the conductor is:
A. 12 C
B. 180 C
C. 720 C
D. 1200 C
Answer: C
Q = It = 3 × 240 = 720 C.
Q = It = 3 × 240 = 720 C.
Q22. A 12 Ω resistor is connected to a 24 V supply. The current is:
A. 0.5 A
B. 1 A
C. 2 A
D. 12 A
Answer: C
I = V/R = 24/12 = 2 A.
I = V/R = 24/12 = 2 A.
Q23. A 5 Ω resistor carries 2 A current. Its power consumption is:
A. 5 W
B. 10 W
C. 20 W
D. 25 W
Answer: C
P = I²R = 2² × 5 = 20 W.
P = I²R = 2² × 5 = 20 W.
Q24. A resistor of 10 Ω is connected across 20 V. The electrical energy consumed in 5 s is:
A. 20 J
B. 100 J
C. 200 J
D. 400 J
Answer: C
P = V²/R = 400/10 = 40 W; W = Pt = 40 × 5 = 200 J.
P = V²/R = 400/10 = 40 W; W = Pt = 40 × 5 = 200 J.
Q25. A cell has emf 12 V and internal resistance 2 Ω. It is connected to an external resistance of 4 Ω. The current is:
A. 1 A
B. 2 A
C. 3 A
D. 6 A
Answer: B
I = ε/(R+r) = 12/(4+2) = 2 A.
I = ε/(R+r) = 12/(4+2) = 2 A.
Q26. For the cell in Q25, the terminal voltage while supplying current is:
A. 4 V
B. 6 V
C. 8 V
D. 12 V
Answer: C
V = IR = 2 × 4 = 8 V, also ε − Ir = 12 − 2×2 = 8 V.
V = IR = 2 × 4 = 8 V, also ε − Ir = 12 − 2×2 = 8 V.
Q27. Three identical cells, each of emf 2 V and internal resistance 1 Ω, are connected in series aiding. Their equivalent emf and internal resistance are:
A. 2 V, 3 Ω
B. 6 V, 1 Ω
C. 6 V, 3 Ω
D. 3 V, 2 Ω
Answer: C
εeq = nε = 6 V; req = nr = 3 Ω.
εeq = nε = 6 V; req = nr = 3 Ω.
Q28. Four identical cells, each of internal resistance 2 Ω, are connected in parallel. The equivalent internal resistance is:
A. 8 Ω
B. 4 Ω
C. 2 Ω
D. 0.5 Ω
Answer: D
For n identical cells in parallel, req = r/n = 2/4 = 0.5 Ω.
For n identical cells in parallel, req = r/n = 2/4 = 0.5 Ω.
Q29. A wire of resistance R is cut into two equal pieces. The resistance of each piece is:
A. R
B. R/2
C. 2R
D. R/4
Answer: B
Halving the length while keeping material and area unchanged halves the resistance.
Halving the length while keeping material and area unchanged halves the resistance.
Q30. The two equal pieces in Q29 are connected in parallel. Their equivalent resistance is:
A. R
B. R/2
C. R/4
D. 2R
Answer: C
Each piece has R/2. Two equal resistances R/2 in parallel give Req = (R/2)/2 = R/4.
Each piece has R/2. Two equal resistances R/2 in parallel give Req = (R/2)/2 = R/4.
Q31. A wire is stretched to twice its original length without changing its volume. If its original resistance is R and resistivity remains unchanged, the new resistance is:
A. R/4
B. R/2
C. 2R
D. 4R
Answer: D
Constant volume makes the area half when length doubles. Thus R' = ρ(2L)/(A/2) = 4R.
Constant volume makes the area half when length doubles. Thus R' = ρ(2L)/(A/2) = 4R.
Q32. In a balanced Wheatstone bridge, P = 2 Ω, Q = 3 Ω and R = 4 Ω. The value of S is:
A. 2 Ω
B. 4 Ω
C. 6 Ω
D. 8 Ω
Answer: C
P/Q = R/S ⇒ 2/3 = 4/S ⇒ S = 6 Ω.
P/Q = R/S ⇒ 2/3 = 4/S ⇒ S = 6 Ω.
Q33. A negative current of −2 A is obtained for a branch while solving Kirchhoff equations. This means:
A. Current is physically impossible
B. The battery has zero emf
C. Actual current is 2 A opposite to the assumed direction
D. Resistance is negative
Answer: C
The assumed reference direction was opposite to the actual current direction.
The assumed reference direction was opposite to the actual current direction.
Q34. If the number density of charge carriers is doubled while A and vd remain unchanged, current becomes:
A. Half
B. Unchanged
C. Double
D. Four times
Answer: C
From I = neAvd, current is directly proportional to n.
From I = neAvd, current is directly proportional to n.
Q35. If the cross-sectional area of a uniform conductor is doubled while its length and resistivity remain unchanged, its resistance becomes:
A. 2R
B. R
C. R/2
D. R/4
Answer: C
Since R ∝ 1/A, doubling A halves R.
Since R ∝ 1/A, doubling A halves R.
3. Competency and Statement-Based MCQs
Q36. A student plots V against I for a resistor and obtains a straight line through the origin. Which conclusion is justified under the stated experimental conditions?
A. The resistor is behaving ohmically over the measured range.
B. Its resistivity must be zero.
C. Its power consumption must be zero.
D. Its current must be independent of voltage.
Answer: A
A straight-line V–I relation through the origin indicates V ∝ I over that measured range, consistent with Ohm's law.
A straight-line V–I relation through the origin indicates V ∝ I over that measured range, consistent with Ohm's law.
Q37. A cell has emf 6 V and internal resistance 1 Ω. When connected to an external resistor, the terminal voltage is measured as 5 V. The current supplied by the cell is:
A. 0.5 A
B. 1 A
C. 5 A
D. 6 A
Answer: B
For a discharging cell, V = ε − Ir. Thus 5 = 6 − I(1), giving I = 1 A.
For a discharging cell, V = ε − Ir. Thus 5 = 6 − I(1), giving I = 1 A.
Q38. Assertion (A): At the balance point of a Wheatstone bridge, the galvanometer current is zero.
Reason (R): The two points connected to the galvanometer are at the same potential.
Reason (R): The two points connected to the galvanometer are at the same potential.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Answer: A
Equal potential at the galvanometer terminals gives zero potential difference and hence zero galvanometer current.
Equal potential at the galvanometer terminals gives zero potential difference and hence zero galvanometer current.
Q39. Assertion (A): The resistance of a uniform wire increases when its length is increased, if material, area and temperature remain unchanged.
Reason (R): Resistance is given by R = ρL/A.
Reason (R): Resistance is given by R = ρL/A.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Answer: A
At fixed ρ and A, the relation R = ρL/A directly shows that R increases with L.
At fixed ρ and A, the relation R = ρL/A directly shows that R increases with L.
Q40. Assertion (A): A negative branch current obtained in a Kirchhoff calculation can be physically meaningful.
Reason (R): The direction of a branch current may be chosen arbitrarily at the beginning of the calculation.
Reason (R): The direction of a branch current may be chosen arbitrarily at the beginning of the calculation.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Answer: A
A negative result indicates that the actual direction is opposite to the assumed reference direction.
A negative result indicates that the actual direction is opposite to the assumed reference direction.
Q41. A resistor is connected to a fixed-voltage source. If its resistance is doubled, its power consumption becomes:
A. Double
B. Half
C. Four times
D. Unchanged
Answer: B
At fixed voltage, P = V²/R. Doubling R halves P.
At fixed voltage, P = V²/R. Doubling R halves P.
Q42. A resistor is connected to a fixed-current source. If its resistance is doubled, its power consumption becomes:
A. Double
B. Half
C. Four times
D. Unchanged
Answer: A
At fixed current, P = I²R. Doubling R doubles P.
At fixed current, P = I²R. Doubling R doubles P.
Q43. Two identical cells are connected in parallel with the same polarity. Compared with one cell, the combination has:
A. Double emf and double internal resistance
B. Same emf and half internal resistance
C. Half emf and same internal resistance
D. Zero emf
Answer: B
For two identical cells in parallel, εeq = ε and req = r/2.
For two identical cells in parallel, εeq = ε and req = r/2.
Q44. A wire and a second wire made of the same material have equal lengths, but the second wire has twice the cross-sectional area. Which statement is correct?
A. Both have the same resistance.
B. The second wire has twice the resistance.
C. The second wire has half the resistance.
D. The second wire has four times the resistance.
Answer: C
For the same material and length, R ∝ 1/A.
For the same material and length, R ∝ 1/A.
Q45. A student says: “Because electrons are moving randomly inside a metal, there must always be a net current.” Which response is correct?
A. Correct, because every moving charge creates a current in one fixed direction.
B. Correct, because thermal motion is always directional.
C. Incorrect, because random motion gives zero average drift velocity in the absence of an applied field.
D. Incorrect, because electrons never move inside metals.
Answer: C
Random thermal motion does not produce a net directional flow. A net current requires a non-zero average drift velocity.
Random thermal motion does not produce a net directional flow. A net current requires a non-zero average drift velocity.
4. Quick Answer Key
| Q | Ans | Q | Ans | Q | Ans |
|---|---|---|---|---|---|
| 1 | B | 16 | B | 31 | D |
| 2 | A | 17 | D | 32 | C |
| 3 | C | 18 | D | 33 | C |
| 4 | B | 19 | B | 34 | C |
| 5 | B | 20 | B | 35 | C |
| 6 | B | 21 | C | 36 | A |
| 7 | A | 22 | C | 37 | B |
| 8 | B | 23 | C | 38 | A |
| 9 | C | 24 | C | 39 | A |
| 10 | B | 25 | B | 40 | A |
| 11 | C | 26 | C | 41 | B |
| 12 | A | 27 | C | 42 | A |
| 13 | B | 28 | D | 43 | B |
| 14 | C | 29 | B | 44 | C |
| 15 | B | 30 | C | 45 | C |
Score interpretation for self-practice: Use your score diagnostically rather than as a prediction of board performance. For every incorrect answer, return to the relevant concept in the Notes and then retry the question without looking at the explanation.
5. What to Revise After This MCQ Set
- Missed Questions 1–7: revise current, current density, drift velocity and mobility.
- Missed Questions 8–16: revise resistance, resistivity, conductivity, Ohm's law and temperature dependence.
- Missed Questions 17–24: revise electrical power, energy and basic numerical relations.
- Missed Questions 25–31: revise emf, internal resistance, cells and resistance transformations.
- Missed Questions 32–40: revise Wheatstone bridge and Kirchhoff reasoning.
- Missed Questions 41–45: focus on application-based reasoning rather than formula recall.
Use the chapter resources in this order
6. Official CBSE Resources
- CBSE Physics Curriculum 2026–27
- CBSE Class XII Sample Question Papers & Marking Schemes 2026–27
- CBSE Question Paper Archive
Source note: The syllabus scope was checked against the official CBSE 2026–27 Physics curriculum. CBSE's current Class XII SQP/MS page was also checked. The MCQs, answer explanations and numerical situations on this page are original Learn Revise Hub practice material. Questions from third-party sites were used only to identify common practice patterns and content gaps, not copied.
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