Current Electricity

Class 12

26 previous-year questions from this chapter every option and the correct answer, free · where the marks are

1. Ohm's law, resistivity, temperature dependence

Exam focus: Resistivity is a property of the material only — stretching a wire to twice its length doubles R (since R = ρl/A) but leaves ρ itself unchanged, and resistivity rises with temperature for metals but falls for semiconductors.

Current Electricity 03: Effect of Temperature on Resistance/Resistivity

Physics Wallah - Alakh Pandey

Covers the ρ–T behaviour for conductors vs semiconductors — the part of this subtopic NEET actually tests — after a quick recap of Ohm's law and R = ρl/A.

PhysicsNEET 2025show ▾

A wire of resistance

R

is cut into 8 equal pieces. From these pieces two equivalent resistances are made by adding four of them together in parallel. Then these two sets are added in series. The net effective resistance of the combination is:

A. $\frac{R}{64}$
B. $\frac{R}{32}$
C. $\frac{R}{16}$ ✓
D. $\frac{R}{8}$

Solution

Each piece is $\frac{R}{8}$ . Four in parallel give $\frac{R}{32}$ ; two such sets in series give $\frac{R}{16}$ .

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PhysicsNEET 2024show ▾

A wire of length

l

and resistance

100 Ω

is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:

A. $52Ω$ ✓
B. $55Ω$
C. $60Ω$
D. $26Ω$

Solution

Each part is $10Ω$ . Five in series give $50Ω$ ; five in parallel give $2Ω$ ; the two groups in series give $50 + 2 = 52$ $Ω$ .

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PhysicsNEET 2023show ▾

The resistance of a carbon resistor determined from colour codes is

(22000 \pm 5%) Ω

. The colour of the third band must be:

A.Red
B.Green
C.Orange✓
D.Yellow

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PhysicsNEET 2023show ▾

The resistance of a platinum wire at

0^{\circ}

C is

2Ω

and

6.8Ω

at

8 0^{\circ}

C. The temperature coefficient of resistance of the wire is:

A. $3 \times 1 0^{- 4}^{\circ} C^{- 1}$
B. $3 \times 1 0^{- 3}^{\circ} C^{- 1}$
C. $3 \times 1 0^{- 2}^{\circ} C^{- 1}$ ✓
D. $3 \times 1 0^{- 1}^{\circ} C^{- 1}$

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PhysicsNEET 2022show ▾

Two resistors of resistance

100Ω

and

200Ω

are connected in parallel in an electrical circuit. The ratio of the thermal energy developed in

100Ω

to that in

200Ω

in a given time is:

A.4 : 1
B.1 : 2
C.2 : 1✓
D.1 : 4

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PhysicsNEET 2022show ▾

A copper wire of length 10 m and radius

(\frac{1 0 ^{- 2}}{π})

m has electrical resistance of

10Ω

. The current density in the wire for an electric field strength of 10 V/m is:

A. $1 0^{5} A/ m^{2}$ ✓
B. $1 0^{4} A/ m^{2}$
C. $1 0^{6} A/ m^{2}$
D. $1 0^{- 5} A/ m^{2}$

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PhysicsNEET 2022show ▾

As the temperature increases, the electrical resistance:

A.Decreases for conductors but increases for semiconductors
B.Increases for both conductors and semiconductors
C.Decreases for both conductors and semiconductors
D.Increases for conductors but decreases for semiconductors✓

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PhysicsNEET 2021show ▾

Column-I gives certain physical terms associated with the flow of current through a metallic conductor. Column-II gives some mathematical relations involving electrical quantities. Match Column-I and Column-II with appropriate relations.

Column-I	Column-II
(A) Drift velocity	(P) $\frac{m}{n e ^{2} ρ}$
(B) Electrical resistivity	(Q) $n e v_{d}$
(C) Relaxation period	(R) $\frac{e E}{m} τ$
(D) Current density	(S) $\frac{E}{J}$

A.(A)-(R), (B)-(S), (C)-(P), (D)-(Q)✓
B.(A)-(R), (B)-(S), (C)-(Q), (D)-(P)
C.(A)-(R), (B)-(P), (C)-(S), (D)-(Q)
D.(A)-(R), (B)-(Q), (C)-(S), (D)-(P)

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PhysicsNEET 2021show ▾

The effective resistance of a parallel connection that consists of four wires of equal length, equal area of cross-section and the same material is

0.25Ω

. What will be the effective resistance if they are connected in series?

A. $0.25Ω$
B. $0.5Ω$
C. $1Ω$
D. $4Ω$ ✓

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PhysicsNEET 2020show ▾

A charged particle having a drift velocity of

7.5 \times 1 0^{- 4} m s^{- 1}

in an electric field of

3 \times 1 0^{- 10} V m^{- 1}

has a mobility, in

m^{2} V^{- 1} s^{- 1}

, of:

A. $2.25 \times 1 0^{15}$
B. $2.5 \times 1 0^{6}$ ✓
C. $2.5 \times 1 0^{- 6}$
D. $2.25 \times 1 0^{- 15}$

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PhysicsNEET 2020show ▾

Which of the following graphs represents the variation of resistivity (

ρ

) with temperature (

T

) for copper?

A.Graph (1)
B.Graph (2)
C.Graph (3)✓
D.Graph (4)

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PhysicsNEET 2020show ▾

The colour code of a resistor is given below. Question 164 as printed in the NEET 2020 booklet

Question 164 as printed in the NEET 2020 booklet

The values of resistance and tolerance, respectively, are:

A. $470 k Ω, 5$ %
B. $47 k Ω, 10$ %
C. $4.7 k Ω, 5$ %
D. $470Ω, 5$ %✓

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PhysicsNEET 2019show ▾

Circuit 1 has a 10 V source driving current

i_{1}

through

a 10Ω

resistor, with an ideal ammeter

A_{1}

in series and an ideal voltmeter

V_{1}

connected across the resistor-and-ammeter combination. Circuit 2 has the same 10 V source,

10Ω

resistor and current

i_{2}

, with ideal ammeter

A_{2}

in series, but this time ideal voltmeter

V_{2}

is connected across the resistor alone (not including the ammeter). The readings of the voltmeters and ammeters will be:

A. $V_{2} > V_{1}$ and $i_{1} = i_{2}$
B. $V_{1} = V_{2}$ and $i_{1} > i_{2}$
C. $V_{1} = V_{2}$ and $i_{1} = i_{2}$ ✓
D. $V_{2} > V_{1}$ and $i_{1} > i_{2}$

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2. Cells, EMF, internal resistance, combinations

Exam focus: Terminal voltage equals EMF only on open circuit — the moment current is drawn, V = E − Ir is strictly less than E. Cells in series suit a large external resistance; cells in parallel suit a small one, where less internal resistance matters most.

Combination of Cells: Series, Parallel and Mixed Grouping

Physics Wallah - Alakh Pandey

Thorough lecture on series, parallel and mixed grouping of cells with derivations and numericals; assumes basic EMF/internal-resistance definitions from the preceding lecture.

3. Kirchhoff's rules, Wheatstone bridge, potentiometer

Exam focus: A potentiometer's advantage over a voltmeter is that, at balance, it draws zero current from the cell being measured, while a voltmeter always draws some and reads slightly low. In a balanced Wheatstone bridge, only the galvanometer branch carries zero current.

Kirchhoff's Laws, Wheatstone Bridge & Potentiometer

LearnoHub - Class 11, 12

One pass through all three: Kirchhoff's junction and loop rules, the Wheatstone bridge balance condition, and the potentiometer's null-point comparison principle.

PhysicsNEET 2025show ▾

The current passing through the battery in the given circuit is: Question 6 as printed in the NEET 2025 booklet

Question 6 as printed in the NEET 2025 booklet

A.2.0 A
B.0.5 A✓
C.2.5 A
D.1.5 A

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PhysicsNEET 2025show ▾

A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is: Question 36 as printed in the NEET 2025 booklet

Question 36 as printed in the NEET 2025 booklet

A.1.5 A
B.2.0 A✓
C.2.5 A
D.3.0 A

Solution

C and D are joined by a wire, so they are at a common potential $V$ (take $V_{A} = 0$ , $V_{B} = 50$ V). Current balance at that node: $\frac{V}{1} + \frac{V}{3} = \frac{50 - V}{2} + \frac{50 - V}{4} \Rightarrow \frac{4 V}{3} = \frac{3 ( 50 - V )}{4} \Rightarrow V = 18$ V. Into C through $1Ω : 18 A$ ; out of C through $2Ω : 16 A$ . The difference, 2.0 A, flows along CD.

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PhysicsNEET 2024show ▾

Choose the correct circuit (from the four given) which can achieve the bridge balance. Question 44 as printed in the NEET 2024 booklet

Question 44 as printed in the NEET 2024 booklet

A.Circuit (1)
B.Circuit (2)
C.Circuit (3)
D.Circuit (4)✓

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PhysicsNEET 2023show ▾

If the galvanometer G does not show any deflection in the circuit shown, the value of

R

is given by: Question 7 as printed in the NEET 2023 booklet

Question 7 as printed in the NEET 2023 booklet

A. $200Ω$
B. $50Ω$
C. $100Ω$ ✓
D. $400Ω$

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PhysicsNEET 2023show ▾

The magnitude and direction of the current in the following circuit is: Question 33 as printed in the NEET 2023 booklet

Question 33 as printed in the NEET 2023 booklet

A.0.2 A from B to A through E
B.0.5 A from A to B through E✓
C. $\frac{5}{9}$ A from A to B through E
D.1.5 A from B to A through E

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PhysicsNEET 2022show ▾

A Wheatstone bridge is used to determine the value of an unknown resistance

X

by adjusting the variable resistance

Y

as shown in the figure. For the most precise measurement of

X

, the resistances

P

and

Q

:

Question 41 as printed in the NEET 2022 booklet

A.Do not play any significant role
B.Should be approximately equal to $2 X$
C.Should be approximately equal and are small✓
D.Should be very large and unequal

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PhysicsNEET 2021show ▾

Three resistors having resistances

r_{1}

,

r_{2}

and

r_{3}

are connected as shown in the given circuit. The ratio

\frac{i _{3}}{i _{1}}

of currents in terms of the resistances used in the circuit is: Question 38 as printed in the NEET 2021 booklet

Question 38 as printed in the NEET 2021 booklet

A. $\frac{r _{1}}{r _{2} + r _{3}}$
B. $\frac{r _{2}}{r _{2} + r _{3}}$ ✓
C. $\frac{r _{1}}{r _{1} + r _{2}}$
D. $\frac{r _{2}}{r _{1} + r _{3}}$

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PhysicsNEET 2021show ▾

In a potentiometer circuit a cell of emf 1.5 V gives a balance point at 36 cm length of wire. If another cell of emf 2.5 V replaces the first cell, then at what length of the wire does the balance point occur?

A.60 cm✓
B.21.6 cm
C.64 cm
D.62 cm

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PhysicsNEET 2020show ▾

A resistance wire connected in the left gap of a metre bridge balances

a 10Ω

resistance in the right gap at a point which divides the bridge wire in the ratio 3 : 2. If the length of the resistance wire is 1.5 m, then the length of

1Ω

of the resistance wire is:

A. $1.0 \times 1 0^{- 2}$ m
B. $1.0 \times 1 0^{- 1}$ m✓
C. $1.5 \times 1 0^{- 1}$ m
D. $1.5 \times 1 0^{- 2}$ m

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