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Current Electricity Class 12 Physics Assertion Reason Questions 2026-27
Current Electricity Class 12 Physics: Assertion–Reason Questions 2026–27
Practise these 30 original CBSE-style Assertion–Reason questions covering the full Current Electricity syllabus. These are original practice questions, not claimed as official CBSE questions or previous-year questions.
Practise these 30 original CBSE-style Assertion–Reason questions covering the full Current Electricity syllabus. These are original practice questions, not claimed as official CBSE questions or previous-year questions.
CBSE scope: The 2026–27 CBSE Physics curriculum includes current and drift velocity, mobility, current density, Ohm's law and V-I characteristics, power and energy, resistivity and conductivity, temperature dependence, emf and internal resistance, combinations of cells, Kirchhoff's rules and Wheatstone bridge. Unit II Current Electricity carries 17 marks at unit level; CBSE does not assign a separate fixed chapter-only weightage in the curriculum.
How to Use Assertion–Reason Questions
First decide whether the Assertion is true or false. Then decide whether the Reason is true or false. Only after that should you check whether the Reason correctly explains the Assertion.
30 Current Electricity Assertion–Reason Questions
Q1. Assertion (A): Conventional current in a metallic conductor is opposite to the drift direction of free electrons.
Reason (R): Reason (R): Electrons carry negative charge, so their drift direction is opposite to the direction assigned to conventional current.
Answer: A
Both statements are true, and the negative charge of electrons makes their drift direction opposite to conventional current.
Both statements are true, and the negative charge of electrons makes their drift direction opposite to conventional current.
Q2. Assertion (A): The current through a conductor can remain constant even when the number of charge carriers crossing a section per second changes.
Reason (R): Reason (R): Electric current is defined as the rate of flow of charge, I = ΔQ/Δt.
Answer: D
The assertion is false because a change in charge crossing per unit time changes the current. The reason is true.
The assertion is false because a change in charge crossing per unit time changes the current. The reason is true.
Q3. Assertion (A): For a given conductor, current density is directly proportional to the drift velocity of its charge carriers.
Reason (R): Reason (R): J = nqv_d for a conductor containing charge carriers of number density n and charge magnitude q.
Answer: A
The equation directly shows the proportionality when n and q are fixed.
The equation directly shows the proportionality when n and q are fixed.
Q4. Assertion (A): Drift velocity of electrons in a metallic wire is generally very small compared with the random thermal velocity of electrons.
Reason (R): Reason (R): Drift velocity is the average directed velocity produced by the applied electric field.
Answer: A
Drift is a small directed component superimposed on random microscopic motion.
Drift is a small directed component superimposed on random microscopic motion.
Q5. Assertion (A): Increasing the length of a uniform wire while keeping its material and cross-sectional area unchanged increases its resistance.
Reason (R): Reason (R): For a uniform wire, R = ρL/A.
Answer: A
Resistance is directly proportional to length for fixed material and area.
Resistance is directly proportional to length for fixed material and area.
Q6. Assertion (A): Two wires made of the same material can have different resistivities.
Reason (R): Reason (R): Resistivity depends on the material and its physical condition, such as temperature, rather than only on the dimensions of the wire.
Answer: D
For the same material under the same physical condition, resistivity is the same; changing dimensions changes resistance, not resistivity. The reason is true.
For the same material under the same physical condition, resistivity is the same; changing dimensions changes resistance, not resistivity. The reason is true.
Q7. Assertion (A): The V-I graph of an ohmic conductor at constant temperature is a straight line passing through the origin.
Reason (R): Reason (R): Ohm's law gives V = IR when physical conditions such as temperature remain constant.
Answer: A
At constant resistance, V is directly proportional to I, so the graph is linear through the origin.
At constant resistance, V is directly proportional to I, so the graph is linear through the origin.
Q8. Assertion (A): A non-ohmic device may have a curved V-I characteristic.
Reason (R): Reason (R): In a non-ohmic device, the ratio V/I need not remain constant as the operating point changes.
Answer: A
A changing V/I ratio means the slope/relationship is not linear, producing a non-linear characteristic.
A changing V/I ratio means the slope/relationship is not linear, producing a non-linear characteristic.
Q9. Assertion (A): Conductivity is the reciprocal of resistivity.
Reason (R): Reason (R): Conductivity is represented by σ and resistivity by ρ, with σ = 1/ρ.
Answer: A
The stated relation directly establishes the reciprocal relationship.
The stated relation directly establishes the reciprocal relationship.
Q10. Assertion (A): If the temperature coefficient of a metallic resistor is positive, its resistance increases with temperature over the stated range.
Reason (R): Reason (R): For a positive temperature coefficient, R = R₀[1 + α(T − T₀)] gives an increase in R when T increases.
Answer: A
With α > 0, the bracketed factor increases as temperature rises.
With α > 0, the bracketed factor increases as temperature rises.
Q11. Assertion (A): Electrical power supplied to a resistor can be written as P = I²R.
Reason (R): Reason (R): Electrical power is the rate of electrical energy transfer and P = VI; using V = IR gives P = I²R.
Answer: A
The reason derives the asserted expression from the definitions and Ohm's law.
The reason derives the asserted expression from the definitions and Ohm's law.
Q12. Assertion (A): For a resistor connected to a fixed voltage source, increasing its resistance decreases the power dissipated.
Reason (R): Reason (R): At fixed voltage, P = V²/R.
Answer: A
At constant V, power is inversely proportional to resistance.
At constant V, power is inversely proportional to resistance.
Q13. Assertion (A): The emf of a cell is equal to its terminal potential difference when no current is drawn from the cell.
Reason (R): Reason (R): With zero current, the internal potential drop Ir is zero, so terminal voltage equals emf.
Answer: A
For an idealized cell with internal resistance r, V = ε − Ir during discharge; at I = 0, V = ε.
For an idealized cell with internal resistance r, V = ε − Ir during discharge; at I = 0, V = ε.
Q14. Assertion (A): During discharge of a cell, its terminal voltage is generally less than its emf when the internal resistance is non-zero.
Reason (R): Reason (R): The terminal voltage during discharge is V = ε − Ir.
Answer: A
The internal drop Ir reduces the terminal voltage below emf for non-zero current.
The internal drop Ir reduces the terminal voltage below emf for non-zero current.
Q15. Assertion (A): When identical cells are connected in series aiding, their emfs add.
Reason (R): Reason (R): The potential rises provided by each cell act in the same direction around the circuit.
Answer: A
Series-aiding cells contribute their emfs in the same direction, so the total emf is the sum.
Series-aiding cells contribute their emfs in the same direction, so the total emf is the sum.
Q16. Assertion (A): Connecting identical cells in parallel increases the emf of the combination.
Reason (R): Reason (R): For identical cells connected in parallel, the equivalent emf remains equal to the emf of one cell.
Answer: D
The assertion is false. Identical parallel cells retain the same emf, although their ability to supply current can increase.
The assertion is false. Identical parallel cells retain the same emf, although their ability to supply current can increase.
Q17. Assertion (A): Kirchhoff's junction rule is based on conservation of charge.
Reason (R): Reason (R): Charge cannot continuously accumulate at an ideal junction in a steady circuit.
Answer: A
The algebraic sum of currents at a junction is zero because charge is conserved.
The algebraic sum of currents at a junction is zero because charge is conserved.
Q18. Assertion (A): Kirchhoff's loop rule is based on conservation of energy.
Reason (R): Reason (R): Around a closed loop, the algebraic sum of potential changes is zero.
Answer: A
The zero net potential change around a closed loop expresses energy conservation per unit charge.
The zero net potential change around a closed loop expresses energy conservation per unit charge.
Q19. Assertion (A): In applying Kirchhoff's rules, the sign of a potential change depends on the chosen direction of traversal.
Reason (R): Reason (R): Crossing a cell from negative to positive terminal is a potential rise, whereas crossing from positive to negative terminal is a potential drop.
Answer: A
The traversal direction determines the sign assigned to each potential change.
The traversal direction determines the sign assigned to each potential change.
Q20. Assertion (A): In a balanced Wheatstone bridge, no current flows through the galvanometer.
Reason (R): Reason (R): At balance, the potentials of the two galvanometer junctions are equal.
Answer: A
Equal potentials across the galvanometer give zero potential difference and hence zero galvanometer current.
Equal potentials across the galvanometer give zero potential difference and hence zero galvanometer current.
Q21. Assertion (A): The balance condition of a Wheatstone bridge is independent of the resistance of the galvanometer.
Reason (R): Reason (R): At balance, the potential difference across the galvanometer is zero, so its current is zero.
Answer: A
Since the galvanometer carries no current at balance, its resistance does not affect the balance condition.
Since the galvanometer carries no current at balance, its resistance does not affect the balance condition.
Q22. Assertion (A): Replacing a wire by another wire of the same material but twice the length and the same area doubles its resistance.
Reason (R): Reason (R): Resistance is directly proportional to length when resistivity and area are unchanged.
Answer: A
R = ρL/A, so doubling L doubles R.
R = ρL/A, so doubling L doubles R.
Q23. Assertion (A): If the radius of a uniform wire is doubled while its length and material remain unchanged, its resistance becomes one-fourth.
Reason (R): Reason (R): The cross-sectional area of a circular wire is proportional to the square of its radius.
Answer: A
Doubling radius makes area four times larger, so R = ρL/A becomes one-fourth.
Doubling radius makes area four times larger, so R = ρL/A becomes one-fourth.
Q24. Assertion (A): A metal wire's resistance generally increases when its temperature rises.
Reason (R): Reason (R): For many metals, the temperature coefficient of resistance is positive over the relevant range.
Answer: A
A positive temperature coefficient produces an increase in resistance with temperature.
A positive temperature coefficient produces an increase in resistance with temperature.
Q25. Assertion (A): A cell can deliver current even though its emf is not a mechanical force.
Reason (R): Reason (R): Emf represents energy supplied by the source per unit charge, and its SI unit is volt.
Answer: A
Emf is not a mechanical force; it is energy per unit charge and is measured in volts.
Emf is not a mechanical force; it is energy per unit charge and is measured in volts.
Q26. Assertion (A): If the current through a resistor is doubled, the power dissipated becomes four times, provided resistance remains constant.
Reason (R): Reason (R): P = I²R.
Answer: A
With fixed R, power is proportional to the square of current.
With fixed R, power is proportional to the square of current.
Q27. Assertion (A): A conductor can obey Ohm's law only if its physical conditions remain appropriately constant.
Reason (R): Reason (R): A change in temperature can change the resistance of many conductors.
Answer: A
Ohm's law applies for fixed physical conditions; temperature changes can alter resistance.
Ohm's law applies for fixed physical conditions; temperature changes can alter resistance.
Q28. Assertion (A): Current density has the same unit as electric current.
Reason (R): Reason (R): Current density is current per unit cross-sectional area, J = I/A.
Answer: D
The assertion is false: current density has SI unit A/m², while current has unit A. The reason is true.
The assertion is false: current density has SI unit A/m², while current has unit A. The reason is true.
Q29. Assertion (A): In a series combination of cells, the same current passes through every cell in the series path.
Reason (R): Reason (R): In a single series path, charge has no alternative branch through which to split.
Answer: A
A series path carries the same current through each element.
A series path carries the same current through each element.
Q30. Assertion (A): For two identical resistors connected in parallel, the equivalent resistance is greater than the resistance of either resistor.
Reason (R): Reason (R): Parallel connection provides more than one path for current.
Answer: D
The assertion is false: two identical resistors R in parallel have equivalent resistance R/2. The reason is true.
The assertion is false: two identical resistors R in parallel have equivalent resistance R/2. The reason is true.
Complete Answer Key
| Q | Ans. | Q | Ans. | Q | Ans. |
|---|---|---|---|---|---|
| 1 | A | 2 | D | 3 | A |
| 4 | A | 5 | A | 6 | D |
| 7 | A | 8 | A | 9 | A |
| 10 | A | 11 | A | 12 | A |
| 13 | A | 14 | A | 15 | A |
| 16 | D | 17 | A | 18 | A |
| 19 | A | 20 | A | 21 | A |
| 22 | A | 23 | A | 24 | A |
| 25 | A | 26 | A | 27 | A |
| 28 | D | 29 | A | 30 | D |
Topic Coverage Checklist
- Current, charge flow and conventional current
- Drift velocity, mobility and current density
- Ohm's law and V-I characteristics
- Resistance, resistivity and conductivity
- Temperature dependence of resistance
- Electrical energy and power
- Emf, terminal potential difference and internal resistance
- Cells in series and parallel
- Kirchhoff's junction and loop rules
- Wheatstone bridge and balance condition
Common Assertion–Reason Traps
- Do not assume that two true statements automatically make option A correct. Check whether R actually explains A.
- Keep current, current density, resistance and resistivity conceptually separate.
- For cells, distinguish emf from terminal potential difference and remember the sign depends on charging or discharging.
- For Wheatstone bridge, focus on equal potentials at the galvanometer junctions at balance.
- For Ohm's law, remember that the relevant physical conditions must remain constant.
Continue Your Current Electricity Preparation
Current Electricity Notes
Important Questions
MCQs
Numericals
Case-Based Questions
Chapter 1 Hub
Chapter 2 Hub
Study sequence: Learn the concept from Notes → practise Important Questions and MCQs → solve Numericals → attempt Case-Based Questions → finish with Assertion–Reason practice.
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