Current Electricity

CBSE Class 12 Physics · every board question from this chapter, 2023–2026 · 35 of them repeated across years

Practice these 139 →

A particle of mass m and charge q starts from rest and moves in an electric field E=E 0 i. After travelling a distance x in the…2026
A wire is gradually stretched to make it 100% longer. Its resistance will increase by:2026
Two wires of same length and same area of cross-section but made of different material of resistivities ρ 1 and ρ 2 are connected…2026
Which of the following characteristics of electrons determines the current in the conductor?2026
A copper wire is stretched to increase its length by 1%. Then the change in its resistance is close to2026
A current of 1.5 A is maintained in a copper wire of length 1 m with area of cross-section 1.7 × 10^-7 m^2. The magnitude of…2026
The resistivity ρ of a metal increases with rise in temperature because:2026
Which of the following statements is true about mobility of charge carriers in a metal?2026
Two heaters rated as (P 1, V) and (P 2, V) are connected in series across a dc source of (V)/2 volt. The power consumed by the…2026
Assertion: The work done, in taking a unit charge around a closed loop of an electric circuit involving cells and resistors in…2026asked 3×
Assertion: In a Wheatstone bridge circuit, if we interchange the position of the cell and the galvanometer, the balance condition…2026asked 3×
Assertion: Two electric heaters of power P 1 and P 2( P 1) are joined in series across a dc source of voltage V. The power…2026asked 3×
An electric iron rated 2‧2 kW, 220V is operated at 110 V supply. Find: (i) its resistance, and (ii) heat produced by it in 10…2026asked 3×
In the given figure, a steady current I flows through the circuit when points A and C are connected by a wire of negligible…2026asked 3×
Calculate the temperature at which the resistance of a conductor becomes 20% more than its resistance at 27 °C. The value of the…2026
What is the order of magnitude of drift velocity of electrons in a conductor? Deduce the relation between the current flowing…2026asked 3×
A heating element using nichrome is connected to a 220 V supply. Initially it draws a current of 2.9 A. After some time, the…2026
Why manganin is used in wire-wound standard resistors? Calculate the temperature at which the resistance of a wire increases by…2026
Establish the relation between drift velocity of electrons (v d) and electric current (I) in a conductor. How is v d affected…2026asked 2×
State Kirchhoff's rules. Using these rules, find the current flowing through branch FC in the given circuit.2026
'Current is a scalar quantity, although we represent current with an arrow.' Explain. Derive the balance condition of a…2026
Explain the statement: "Current is a scalar although we represent current with an arrow". Use Kirchhoff's rules to find the…2026asked 3×
The two Kirchhoff's rules are based on law of conservation of two physical quantities. Name the quantities. Find magnitude and…2026
A student sets up the circuit as shown in the figure to find the value of unknown resistance X and records a set of readings of…2026asked 3×
(i) Derive the condition for which a Wheatstone Bridge is balanced. (ii) Determine the current in 3 Ω branch of a Wheatstone…2026asked 3×
The ratio of potential difference across A B in the circuit shown for the case (i) when switch S is closed and (ii) when S is…2025
The figure shows the voltage (V) versus the current (I) graphs for a wire at two temperatures T 1 and T 2. One can conclude that:2025
A wire of resistance R, connected to an ideal battery consumes a power P. If the wire is gradually stretched to double its…2025
A battery of e. m. f. 12 V and internal resistance 0.5 Ω is connected to a 9.5 Ω resistor through a key. The ratio of potential…2025
A student has three resistors, each of resistance R. To obtain a resistance of 2/3 R, she should connect2025
Three wires A, B and C of the same material have lengths and area of cross-sections as (2 l, ( A)/2),(l, A) and (l/2, 2 A),…2025
Two conductors A and B of the same material have their lengths in the ratio 1: 2 and radii in the ratio 2: 3. If they are…2025
The resistance of a wire of length L and radius r is R. Which one of the following would provide a wire of the same material of…2025
A current flows through a cylindrical conductor of radius R. The current density at a point in the conductor is j=α r (along its…2025
The effective resistance between points A and B in the given circuit is:2025asked 2×
If R s and R p are the equivalent resistances of n resistors, each of value R, in series and parallel combinations respectively,…2025asked 3×
Two wires P and Q are made of the same material. The wire Q has twice the diameter and half the length as that of wire P. If the…2025
When the switch of the circuit is turned on, the filament of the bulb glows instantaneously because:2025
Which pair of readings of ideal voltmeter and ideal ammeter in the given circuit is possible when a suitable power source of 3 Ω…2025
A steady current I is passed through a conductor at room temperature for time t. It is observed that its temperature rises by 0 ·…2025
Four resistors, each of resistance R and a key K are connected as shown in the figure. The equivalent resistance between points A…2025asked 3×
A cell of emf E and internal resistance r is connected to an external variable resistance R. Plot a graph showing the variation…2025
Two wires made of the same material have the same length ( l ) but different cross-sectional areas A 1 and A 2. They are…2025
Find the effective resistance of the network of resistors between points A and F as shown in the figure.2025
Find the equivalent resistance between points A and B for the network shown in the figure.2025
n identical cells, each of e. m. f. E and internal resistance r, are connected in series. Later on it was found out that two…2025
Calculate the value of the current passing through the battery in the given circuit diagram.2025
Show that E=ρ j leads to Ohm's law. Write a condition in which the Ohm's law is not valid for a material.2025
A cell of emf E and internal resistance r is connected across a resistor of variable resistance R. Show graphically the variation…2025
A battery of emf E and internal resistance r is connected to a rheostat. When a current of 2 A is dawn from the battery, the…2025
A wire of resistance X ohm is gradually stretched till its length becomes twice its original length. If its new resistance…2025
What is the difference between 'velocity' and 'drift velocity' of electrons in a current-carrying conductor. A copper wire of…2025
A voltmeter of resistance 1000 Ω can measure up to 25 V. How will you convert it so that it can read up to 250 V?2025
In the given figure, three identical bulbs P, Q and S are connected to a battery. (i) Compare the brightness of bulbs P and Q…2025asked 3×
Two wires of the same material and the same radius have their lengths in the ratio 2: 3. They are connected in parallel to a…2025asked 3×
The resistance of a wire at 25^° C is 10 · 0 Ω. When heated to 125^° C, its resistance becomes 10 · 5 Ω. Find (i) the temperature…2025
Two batteries of emf's 3 V \& 6 V and internal resistances 0.2 Ω & 0.4 Ω are connected in parallel. This combination is connected…2025asked 3×
Define Electrical conductivity. Obtain the expression of electrical conductivity of a conductor in terms of number density and…2025
What is the difference between 'emf' and 'terminal voltage' of a cell? Two cells of emfs E 1 and E 2 and internal resistances r 1…2025
(i) Derive an expression for the resistivity of a conductor in terms of number density of free electrons and relaxation time.…2025asked 3×
A cell of e. m. f. E and internal resistance r is connected with a variable external resistance R and a voltmeter showing…2025
Three cells A, B and C of emfs 2 V, 3 V and 5 V respectively are connected in parallel to each other. Their internal resistances…2025
Define the term'drift velocity'of conduction electrons in a conductor. A conductor of length l and area of cross-section A is…2025
Define resistivity of a conductor. Discuss its dependence on temperature of the conductor and draw a plot of resistivity of…2025
State Kirchhoff's laws. Apply these laws to find the values of current flowing in the three branches of the given circuit.2025
In a metallic conductor, an electron, moving due to thermal motion, suffers collisions with the heavy fixed ions but after…2025asked 3×
A circuit consisting of a capacitor C, a resistor of resistance R and an ideal battery of emf V, as shown in figure is known as…2025asked 3×
(i) Three batteries E 1, E 2 and E 3 of emfs and internal resistances ( 4 V, 2 Ω ), ( 2 V, 4 Ω ) and ( 6 V, 2 Ω ) respectively…2025asked 3×
An ammeter and a voltmeter are connected in series to a battery. Their readings are noted as 'A' and 'V' respectively. If a…2024
A heater coil rated as ( P, V ) is cut into two equal parts. One of the parts is then connected to a battery of V volt. The power…2024
A battery supplies 0.9 A current through a 2 Ω resistor and 0.3 A current through a 7 Ω resistor when connected one by one. The…2024
Two charged particles P and Q, having the same charge but different masses m P and m Q, start from rest and travel equal…2024
Electrons drift with speed v d in a conductor with potential difference V across its ends. If V is reduced to ((V)/2), their…2024asked 3×
In a uniform straight wire, conduction electrons move along +x direction. Let E and j be the electric field and current density…2024
A student is asked to connect four cells, each of emf E and internal resistance r, in series. But she/he connects one cell…2024
Consider the circuit shown in the figure. The potential difference between points A and B is:2024
Assertion: The temperature coefficient of resistance is positive for metals and negative for p -type semiconductors. Reason (R):…2024asked 3×
Assertion: When electrons drift in a conductor, it does not mean that all free electrons in the conductor are moving in the same…2024asked 3×
What is meant by 'relaxation time' of free electrons in a conductor? Show that the resistance of a conductor can be expressed by…2024asked 3×
Define resistivity of a conductor. How does the resistivity of a conductor depend upon the following: Number density of free…2024
A uniform wire of length L and area of cross-section A has resistance R. The wire is uniformly stretched so that its length…2024
An electric field E is maintained in a wire of length ' l ' and area of cross-section 'a'. Derive the relation between the…2024
Find the temperature at which the resistance of a wire made of silver will be twice its resistance at 20^° C. Take 20^° C as the…2024
Two batteries of emfs 6 V and 3 V and internal resistances 0 · 8 Ω and 0 · 2 Ω respectively are connected in series to an…2024
"The electron drift speed is only a few mm / s for currents in the range of a few amperes for a given conductor." How then is…2024
Two electric heaters have power ratings P 1 and P 2, at voltage V. They are connected in series to a dc source of voltage V. Find…2024
Two wires A and B of different metals have their lengths in ratio 1: 2 and their radii in ratio 2:1 respectively. I-V graphs for…2024
Find the temperature at which the resistance of a conductor increases by 25% of its value at 27 °C. The temperature coefficient…2024
Plot a graph showing the variation of current with voltage for the material GaAs. On the graph, mark the region where: resistance…2024
Determine the current in branches AB, AC and BC of the network shown in figure.2024
The figure shows a circuit with three ideal batteries. Find the magnitude and direction of currents in the branches AG, BF and CD.2024asked 3×
A battery of unknown emf E and internal resistance r is connected in a circuit as shown in the figure. When the key ( K ) is…2024
A current of 1.6 A flows through a wire when a potential difference of 1.0 V is applied across it. The length and cross-sectional…2024
Define 'current density'. Is it a scalar or a vector? An electric field E is maintained in a metallic conductor. If n be the…2024asked 3×
(i) Define 'temperature coefficient of resistance' of a metal. (ii) Show the variation of resistivity of copper with rise in…2024
In the given network, calculate: (i) effective resistance between points A and M, and (ii) power supplied by the battery.2024
Find the current in branch BM in the network shown:2024
Find the currents flowing through the branches AB and BC in the network shown.2024
A potential difference of 1.0 V is applied across a conductor of length 5.0 m and area of cross-section 1.0 mm^2. When current of…2024
When the terminals of a cell are connected to a conductor of resistance R, an electric current flows through the circuit. The…2024asked 3×
A battery of emf E and internal resistance r is connected to an external circuit. The potential drop within the battery is…2023
A steady current flows through a metallic wire whose area of cross-section increases continuously from one end of the wire to the…2023asked 3×
Which one of the following is not a scalar quantity?2023
For a metallic conductor, the correct representation of variation of resistance R with temperature T is:2023
The current density due to drift of electrons in a conductor is given by: (symbols have their usual meanings)2023
A current of 0.8 A flows in a conductor of 40 Ω for 1 minute. The heat produced in the conductor will be2023
The potential difference across a cell in an open circuit is 8 V. It falls to 4 V when a current of 4 A is drawn from it. The…2023
A cell of emf E is connected across an external resistance R. When current ' I ' is drawn from the cell, the potential difference…2023asked 3×
Two wires of equal length and radii r and 2 r are connected in series. Their resistivities are 2 ρ and ρ respectively. For the…2023
A steady current of 8 mA flows through a wire. The number of electrons passing through a cross-section of the wire in 10 s is2023
The SI unit of mobility of charge carriers is:2023
A conductor of 10 Ω is connected across a 6 V ideal source. The power supplied by the source to the conductor is2023
The number of electrons flowing through a conductor per second is 3 · 3 × 10^19. The current flowing through the conductor is:2023
The current in a device varies with time t as I=6 t, where I is in mA and t is in s. The amount of charge that passes through the…2023
The emf and internal resistance of a cell are E and r respectively. It is connected across an external resistance R=2 r. The…2023
Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of2023
Which one of the following is the correct representation of variation of conductivity of a conductor with temperature?2023
Two cells of emf E each and internal resistances r and 2 r are connected in parallel as shown in the figure. The equivalent emf…2023
The correct graph showing the variation of the resistance (R) of a cylindrical metal wire as a function of its radius ( r ),…2023
Assertion: When three electric bulbs of power 200 W, 100 W and 50 W are connected in series to a source, the power consumed by…2023asked 3×
Assertion: The internal resistance of a cell is constant. Reason (R): Ionic concentration of the electrolyte remains same during…2023asked 3×
Assertion: The given figure does not show a balanced Wheatstone bridge. Reason (R): For a balanced bridge small current should…2023
Assertion: The equivalent resistance between points A and B in the given network is 2 R. Reason (R): All the resistors are…2023asked 2×
Write two differences between the emf and terminal potential difference of a cell. What is the most important precaution that one…2023
A cell of emf E and internal resistance r is connected to a variable resistance R. Draw plots showing the variation of terminal…2023
Two conductors, made of the same material have equal lengths but different cross-sectional areas A 1 and A 2( A 1 A 2). They are…2023
The potential difference applied across a given conductor is doubled. How will this affect (i) the mobility of electrons and (ii)…2023
A potential difference ( V ) is applied across a conductor of length ' L ' and cross-sectional area 'A'. How will the drift…2023
Two identical cells, each of emf E and internal resistance r, are connected with a load resistance R, first in series and then in…2023
A potential difference V is applied across a conductor of length l and uniform cross-section area A. How will the (i) electric…2023
Define current density and relaxation time. Derive an expression for resistivity of a conductor in terms of number density of…2023
Two cells of emf E 1 and E 2 and internal resistances r 1 and r 2 are connected in parallel, with their terminals of the same…2023
A potential difference V is applied across a conductor of length l and cross- sectional area A. Briefly explain how the current…2023
Obtain a relation between the current flowing in a conductor and drift velocity of electrons in it. Hence, obtain Ohm's law.2023
A potential difference ' V ' is applied across a load resistor of resistance R. V and R can be varied. If the current that flows…2023
(i) Explain how free electrons in a metal at constant temperature attain an average velocity under the action of an electric…2023asked 2×
(i) Define mobility of electrons. Give its SI units. (ii) A steady current flows through a wire AB, as shown in the figure. What…2023asked 3×
The following figure shows a circuit diagram. We can find the currents through and potential differences across different…2023asked 3×

Answers come from CBSE’s own marking schemes. How we source them.