Two wires that are made up of two different materials whose specific resistance are in the ratio ${\rm{2 : 3}}$, length ${\rm{3 : 4}}$ and area ${\rm{4 : 5}}$. The ratio of their resistances is

$\begin{array}{*{20}{l}} {{\rm{5 : 8}}} \end{array}$

$\begin{array}{*{20}{l}} {{\rm{6 : 5}}} \end{array}$

$\begin{array}{*{20}{l}} {{\rm{6 : 8}}} \end{array}$

$\begin{array}{*{20}{l}} {{\rm{1 : 2}}} \end{array}$

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JEE • PHYSICS • CURRENT ELECTRICITY

Current electricity practice · Medium

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These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 1-30 of 457 questions

1 Medium

1 of 457

Application +4 | -1

The specific resistance of a wire is

\mathrm{\rho }

, its volume is

3\,\,{\mathrm{m}^3}

and its resistance is

3\,\,\mathrm{\Omega }

, then its length will be

View answer and explanation

Correct option: B

3/\sqrt \mathrm{\rho }

Option B (

3/\sqrt \mathrm{\rho }

) is correct because it is derived from the relationship between resistance, resistivity, volume, and length.

2 Medium

2 of 457

Remembering +4 | -1

Magnitude of drift velocity per unit electric field is

View answer and explanation

Correct option: D

Mobility

Option D (Mobility) is correct because mobility is defined as the drift velocity per unit electric field.

3 Medium

3 of 457

Understanding +4 | -1

Statement-1: If a resistor is connected to a battery the current decreases when the temperature increases.
Statement-2: For most of the resistors, resistance increases with increase in temperature.

View answer and explanation

Correct option: A

Statement-1 is true, Statement-2 is true, Statement-2 is the correct explanation for Statement-1

Option A is correct because the resistance of a resistor increases with temperature, leading to a decrease in current according to Ohm's law.

4 Medium

4 of 457

Remembering +4 | -1

The reciprocal of resistance is

View answer and explanation

Correct option: A

Conductance

Option A (Conductance) is correct because conductance is defined as the reciprocal of resistance.

5 Medium

5 of 457

Application +4 | -1

Corresponding to the resistance

4.7\,\, \times \,\,{10^6}\,\,\mathrm{\Omega }\,\, \pm \,\,5\,\,\%

, which is order of colour coding on carbon resistors?

View answer and explanation

Correct option: B

Yellow, violet, green, gold

Option B (Yellow, violet, green, gold) is correct because it corresponds to the resistance value 4.7 × 10⁶ ohms with a 5% tolerance.

6 Medium

6 of 457

Application +4 | -1

In a meter bridge, the gaps are closed by resistance 2 and 3 ohms. The value of shunt to be added to 3 ohm resistor to shift the balancing point by

22.5\,cm

View answer and explanation

Correct option: B

2\,\Omega

Option B (

2\,\Omega

) is correct because it provides the correct shunt resistance value needed to shift the balancing point by 22.5 cm, based on the Wheatstone bridge principle.

7 Medium

7 of 457

Application +4 | -1

Two wires that are made up of two different materials whose specific resistance are in the ratio

\mathrm{2 : 3}

, length

\mathrm{3 : 4}

and area

\mathrm{4 : 5}

. The ratio of their resistances is

View answer and explanation

Correct option: C

\begin{array}{llllllllllllllllllll} {\mathrm{5 : 8}} \end{array}

Option C (5 : 8) is correct because the ratio of resistances is calculated using the formula R = ρl/A, considering the given ratios of specific resistance, length, and area.

8 Medium

8 of 457

Application +4 | -1

\mathrm{12}\,\,\mathrm{cells}

each having same emf are connected in series with some cells wrongly connected. The arrangement is connected in series with an ammeter and two cells which are in series. Current is

3\,\,A

when cells and battery aid each other and is

2\,\,A

when cells and battery oppose each other. The number of cells wrongly connected is

View answer and explanation

Correct option: B

Option B (1) is correct because solving the system of equations derived from the given conditions yields one wrongly connected cell.

9 Medium

9 of 457

Analyzing +4 | -1

An uncharged capacitor having capacitance

C

is connected across a battery of emf

V

. Now the battery is disconnected and reconnected across same battery but with reverse polarity, then the ratio of total thermal energy produced to the total energy supplied by the battery is

View answer and explanation

Correct option: C

\frac{2}{3}

Option C (

\frac{2}{3}

) is correct because the total thermal energy produced is

2CV^2

and the total energy supplied by the battery is

3CV^2

, giving a ratio of

\frac{2}{3}

10 Medium

10 of 457

Understanding +4 | -1

The net resistance of a voltmeter should be large to ensure that

View answer and explanation

Correct option: D

It does not appreciably change the potential difference to be measured

Option D (It does not appreciably change the potential difference to be measured) is correct because a high resistance voltmeter draws negligible current, minimizing its impact on the circuit.

11 Medium

11 of 457

Application +4 | -1

A silver wire has a resistance of

2.1\, \Omega

27.5^{\circ} {C}

and a resistance of

2.7\, \Omega

100^{\circ} {C}

. Determine the temperature coefficient of resistivity of silver.

View answer and explanation

Correct option: C

0.0039 /{ }^{\circ} {C}

Option C (

0.0039 /{ }^{\circ} {C}

) is correct because it is the temperature coefficient of resistivity calculated using the given resistance values at two different temperatures.

12 Medium

12 of 457

Application +4 | -1

An electric fan and a heater are marked as

100\,\,watt,\,\,220\,\,volt

and

1000\,\,watt,\,\,220\,\,\mathrm{volt}

respectively. The resistance of the heater is

View answer and explanation

Correct option: C

Less than that of the fan

Option C (Less than that of the fan) is correct because resistance is inversely proportional to power for a constant voltage.

13 Medium

13 of 457

Application +4 | -1

A battery has an emf of

\mathrm{15}\,\,\mathrm{V}

and internal resistance of

\mathrm{1}\,\,\mathrm{\Omega }

. Is the terminal to terminal potential difference less than, equal to or greater than

\mathrm{15}\,\,\mathrm{V}

if the current in the battery is

\left( \mathrm{1} \right)

from negative to positive terminal,

\left( \mathrm{2} \right)

from positive to negative terminal

\left( \mathrm{3} \right)

zero current?

View answer and explanation

Correct option: A

Less, grater, equal

Option D (Greater, less, equal) is incorrect. The correct answer is Less, greater, equal. The terminal potential difference depends on the direction of current and internal resistance.

14 Medium

14 of 457

Application +4 | -1

The length of the wire is doubled. Its conductance will be

View answer and explanation

Correct option: B

Halved

Option B (Halved) is correct because conductance is inversely proportional to the length of the wire, so doubling the length halves the conductance.

15 Medium

15 of 457

Understanding +4 | -1

An electric bulb, a capacitor, a battery and a switch are all in series in a circuit. How does the intensity of light vary when the switch is turn on?

View answer and explanation

Correct option: C

Sharply rises initially and then gradually decreases

Option C (Sharply rises initially and then gradually decreases) is correct because initially the capacitor acts as a short circuit, allowing a large current and bright light, but as it charges, the current decreases, dimming the light.

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16 Medium

16 of 457

Understanding +4 | -1

In which of the following substances does resistance decrease with increase in temperatures?

View answer and explanation

Correct option: B

Carbon

Option B (Carbon) is correct because carbon is a semiconductor, and semiconductors typically exhibit a decrease in resistance with increasing temperature due to increased carrier concentration.

17 Medium

17 of 457

Remembering +4 | -1

The Petlier coefficient of a thermo-couple of metls

A

and

B

at junction temperature

T

is given by

View answer and explanation

Correct option: B

T\frac{{dE}}{{dT}}

Option B (

T\frac{{dE}}{{dT}}

) is correct because the Peltier coefficient is defined as the product of the absolute temperature and the rate of change of the electromotive force (EMF) with respect to temperature.

18 Medium

18 of 457

Analyzing +4 | -1

A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it

View answer and explanation

Correct option: A

increases, thermal velocity of the electron decreases

Option D (Decreases, thermal velocity of the electron increases) is correct because as temperature increases, the thermal velocity increases, leading to more collisions and a decrease in drift velocity.

19 Medium

19 of 457

Understanding +4 | -1

Which of the following is not reversible

View answer and explanation

Correct option: A

Joule effect

Option A (Joule effect) is correct because the Joule effect, which involves the generation of heat due to the flow of current through a resistor, is irreversible as heat cannot spontaneously convert back into electrical energy.

20 Medium

20 of 457

Application +4 | -1

A resistor

R

is connected to a parallel combination of two identical batteries each with emf

E

and an internal resistance

r

. The potential drop across the resistance

R

is:

View answer and explanation

Correct option: A

\frac{2 E R}{2 R+r}

Option A (

\frac{2 E R}{2 R+r}

) is correct because it's derived from calculating the equivalent EMF and internal resistance of the parallel battery combination and then applying Ohm's law.

21 Medium

21 of 457

Remembering +4 | -1

Material that is widely used to make wire bound standard resistors is

View answer and explanation

Correct option: A

Manganin

Option A (Manganin) is correct because Manganin has a low temperature coefficient of resistance and high resistivity, making it suitable for wire-wound standard resistors.

22 Medium

22 of 457

Remembering +4 | -1

The correct relation between current density

(\vec{J})

and electric field

(\vec{E})

is

(Where

\rho

is resistivity,

\sigma

is conductivity and

R

is resistance of conductor)

View answer and explanation

Correct option: B

\vec{J}=\sigma \vec{E}

Option B (

\vec{{J}}=\sigma \vec{{E}}

) is correct because it represents the relationship between current density and electric field, where conductivity is the constant of proportionality.

23 Medium

23 of 457

Understanding +4 | -1

A steady current is flowing through a conductor of non-uniform cross-section. The charge passing through any cross-section of it per unit time is:

View answer and explanation

Correct option: D

Independent of the area of cross-section

Option D (Independent of the area of cross-section) is correct because a steady current implies that the charge flow rate is constant throughout the conductor, regardless of the cross-sectional area.

24 Medium

24 of 457

Remembering +4 | -1

Fuse wire is a wire of

View answer and explanation

Correct option: D

High resistance and low melting point

Option D (High resistance and low melting point) is correct because a fuse wire needs to easily melt (low melting point) when excessive current flows due to its high resistance.

25 Medium

25 of 457

Understanding +4 | -1

A piece of copper and a piece of germanium are cooled from room temperature to

80 {~K}

. Then, which one of the following is correct?

View answer and explanation

Correct option: C

Resistance of copper will decrease while that of germanium will increase

Option C (Resistance of copper will decrease while that of germanium will increase) is correct because copper is a metal (resistance decreases with temperature) and germanium is a semiconductor (resistance increases as temperature decreases).

26 Medium

26 of 457

Application +4 | -1

The current of 1.6 A flowing in a conductor. The number of electrons flowing per second through the conductor is

View answer and explanation

Correct option: B

{10^{19}}

Option B (10¹⁹) is correct because it is calculated by dividing the total charge passing through the conductor by the charge of a single electron.

27 Medium

27 of 457

Understanding +4 | -1

Assertion: Fuse wire must have high resig. tance and low melting point.

Reason: Fuse is used for small current flow only.

View answer and explanation

Correct option: C

If Assertion is true but Reason is false.

Option C is correct. A fuse wire must have high resistance to generate heat and a low melting point to break the circuit when the current exceeds a safe level. The reason is false because fuses are used for a range of current flows up to their rated value.

28 Medium

28 of 457

Application +4 | -1

Find the mass of silver liberated in a silver voltameter carrying a current of

1.5 \mathrm{~A}

, during 15 minutes. The electro chemical equivalent of silver is

1.12 \times 10^{-6} \mathrm{~kg} / \mathrm{C}

View answer and explanation

Correct option: A

0.76 g

Option A (0.76 g) is correct because the mass of silver liberated is calculated using Faraday's law of electrolysis, which relates mass, current, time, and electrochemical equivalent.

29 Medium

29 of 457

Application +4 | -1

A current of

16 {~A}

is made to pass through a conductor in which the number density of free electrons is

4 \times 10^{28} {~m}^{-3}

and its area of crosssection is

10^{-5} {~m}^2

. The average drift velocity of free electrons in the conductor is

View answer and explanation

Correct option: A

2.5 \times 10^{-4} {~ms}^{-1}

Option A (

2.5 \times 10^{-4} {~ms}^{-1}

) is correct because it is the result of applying the drift velocity formula using the given values for current, number density, area, and electron charge.

30 Medium

30 of 457

Understanding +4 | -1

The mobility of free electrons (charge

=\mathrm{e}

, mass

=\mathrm{m}

and relaxation time

=\tau

) in a metal is proportional to

View answer and explanation

Correct option: A

\frac{\mathrm{e}}{\mathrm{m}} \tau

The correct answer is A (

\frac{\mathrm{e}}{\mathrm{m}} \tau

) because mobility is defined as drift velocity per unit electric field, which is proportional to charge and relaxation time, and inversely proportional to mass.

Revision notes and key takeaways

Review CURRENT ELECTRICITY in your textbook or class notes, then use this set to check your understanding.

Key Takeaways

✓ This set contains 457 single-correct-answer MCQs on CURRENT ELECTRICITY.
✓ Try each question before opening its answer. Read the explanation where one is available.
✓ Sign in to save submitted answers. Revisit incorrect answers alongside your textbook or class notes.

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