Chapter 11: Electricity

Important questions — the ones the board asked most (20)

1. Q1Long answer5 marksAsked: 2023

   (a) An electric iron consumes energy at a rate of 880 W when heating is at the maximum rate and 330 W when the heating is at the minimum. If the source voltage is 220 V, calculate the current and resistance in each case. (b) What is heating effect of electric current ? (c) Find an expression for the amount of heat produced when a current passes through a resistor for some time.

   

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   Model answer · heating effect of current, numerical

   1. 1.Given: power at maximum heating rate P = 880 W, voltage V = 220 V. Formula: I = P/V Substitution: I = 880 W/220 V Calculation: I = 4 The current for maximum heating rate is 4 A.0.5 marks
   2. 2.Given: V = 220 V, I = 4 A (current at maximum heating rate). Formula: R = V/I Substitution: R = 220 V/4 A Calculation: R = 55 The resistance for maximum heating rate is 55 Ω.0.5 marks
   3. 3.Given: power at minimum heating rate P = 330 W, voltage V = 220 V. Formula: I = P/V Substitution: I = 330 W/220 V Calculation: I = 1.5 The current for minimum heating rate is 1.5 A, which is less than the 4 A found for the maximum heating rate.0.5 marks
   4. 4.Given: V = 220 V, I = 1.5 A (current at minimum heating rate). Formula: R = V/I Substitution: R = 220 V/1.5 A Calculation: R = 146.67 The resistance for minimum heating rate is 146.67 Ω, which is greater than the 55 Ω found for the maximum heating rate.0.5 marks
   5. 5.When electric current is passed through a conductor, the heating of the conductor due to the current is called the heating effect of electric current.1 mark
   6. 6.Consider a current I flowing through a resistor of resistance R. Let the potential difference across it be V. Let t be the time during which a charge Q flows across. The work done in moving the charge Q through a potential difference V is VQ. Therefore, the source must supply energy equal to VQ in time t. The energy supplied to the circuit by the source in time t is VIt. This energy expended by the source gets dissipated in the resistor as heat. Thus for a steady current I, the amount of heat H produced in time t is given by the work done, W = VIt, where V is potential difference, I is current and t is time.1 mark
   7. 7.Applying Ohm's law, V = IR, to the expression for heat, H = VIt, we substitute V = IR to get H = IR × It. This gives the amount of heat produced when a current passes through a resistor for some time as H = I²Rt.1 mark

   • Show the working I = P/V for both cases and write '4 A' and '1.5 A' clearly with units.
   • Show the working R = V/I for both cases and write '55 Ω' and '146.67 Ω' clearly with units.
   • Write the formula W = VIt first, then use Ohm's law V = IR to derive H = I²Rt, naming Ohm's law explicitly, without adding Joule's law or its three proportionality statements.

   Marks split from a structure derived from past papers (checked twice); not CBSE’s official scheme

2. Q2Long answer5 marksAsked: 2026

   39. (a) (i) Consider the following electric circuit : [Circuit Diagram] Calculate the values of the following quantities : (I) Total resistance of the circuit. (II) Total current taken from the source. (III) Potential difference across the 3 Ohm resistor. (ii) Two bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to electric mains. Calculate the current drawn from the mains. OR (b) (i) State Ohm's law and draw V-I graph for a conductor obeying Ohm's law. Show that the slope of this graph provides the resistance of the conductor. (ii) Three resistors with resistances R1, R2 and R3 are connected in series. Derive the expression for the total resistance of the combination.

   

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   Model answer · Ohm's law, resistors in series

   1. 1.(b)(i) Ohm's law: At constant temperature, the potential difference V across a conductor is directly proportional to the current I flowing through it. V ∝ I or V = IR, where R is a constant called the resistance of the conductor.1 mark
   2. 2.V-I graph: Current I goes on the x-axis and potential difference V goes on the y-axis. For a conductor that obeys Ohm's law, the graph is a straight line passing through the origin. This shows that V increases in the same ratio as I.1 mark
   3. 3.Slope of the V-I graph: Take two points on the straight line. Slope = ΔV/ΔI The line passes through the origin, so the slope = V/I. From Ohm's law, V = IR. So V/I = R. The slope of the V-I graph therefore gives the resistance R of the conductor.1 mark
   4. 4.(b)(ii) Three resistors with resistances R1, R2 and R3 are connected in series to a battery of potential difference V. In a series combination, the same current I flows through all three resistors. The total potential difference is the sum of the potential differences V1, V2 and V3 across the three resistors: V = V1 + V2 + V3 ...(1)1 mark
   5. 5.Applying Ohm's law to each resistor separately: V1 = IR1, V2 = IR2, V3 = IR3 Let Rs be the total resistance of the combination. Then V = IRs. Substituting these in (1): IRs = IR1 + IR2 + IR3 Dividing both sides by I: Rs = R1 + R2 + R3 The total resistance of a series combination is the sum of the individual resistances.1 mark

   Diagram: Draw a V-I graph: a straight line starting from the origin O. Label the x-axis "Current I (A)" and the y-axis "Potential difference V (V)". Mark ΔI and ΔV on the line to show the slope.

   • When you state Ohm's law, write "at constant temperature" and "V ∝ I" or "V = IR".
   • Draw the graph as a "straight line passing through the origin" and label the axes V and I.
   • In the series derivation, write "the same current I flows through all three resistors" before you write V = V1 + V2 + V3.

   Marks split from a structure derived from past papers (checked twice); not CBSE’s official scheme

3. Q3Long answer5 marksAsked: 2026

   (A) (i) The given electric circuit is a part of an electrical device. Use the information given in the electric circuit diagram to calculate : (I) Potential difference across the ends of resistor R2. (II) Value of resistor R2. (III) Value of resistor R1. (ii) Write the factors on which resistance of a conductor depends and derive the formula for resistance of a given conductor. OR (B) (i) How much electric current will an electric iron draw from 220 V source if the resistance of its heating element when hot, is 55 ohm ? Calculate the power consumed by the electric iron when it is operated at 220 V. (ii) In a house, 3 bulbs of 100 watt each, are lit for 5 hours daily and an electric heater of 1.0 kW is used for half an hour daily. Calculate the total energy consumed in a month of 30 days and its cost at the rate of 3.60 per kWh. (iii) With reason explain, why alloys commonly used to make elements of electrical heating devices.

   

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   Model answer · Resistors in series and parallel, resistivity

   1. 1.Given: a 12 V supply drives a total current I = 2.0 A through R1, a 2 Ω resistor and a parallel pair made of a 4 Ω resistor (R) and R2, all joined in series. Let I1 = 1.5 A be the current through the 4 Ω resistor and I2 the current through R2. (i) (I) The potential difference across R2 is the same as the potential difference across the 4 Ω resistor, because the two are connected in parallel. V (across R2) = I1 R0.5 marks
   2. 2.V = 1.5 × 40.5 marks
   3. 3.V = 6 V (II) Current through R2: I2 = I − I10.5 marks
   4. 4.I2 = 2.0 − 1.5 = 0.5 A R2 = V / I2 R2 = 6 / 0.5 R2 = 12 Ω0.5 marks
   5. 5.(III) Potential difference across the 2 Ω resistor, which carries the full current: V = I R V = 2 × 2 = 4 V Potential difference across R1 = 12 − (6 + 4) = 2 V0.5 marks
   6. 6.R1 = V / I R1 = 2 / 2 R1 = 1 Ω0.5 marks
   7. 7.(ii) The resistance of a conductor depends on its length, its area of cross-section and the nature of its material. Resistance is directly proportional to the length of the conductor: R ∝ l.0.5 marks
   8. 8.Resistance is inversely proportional to the area of cross-section of the conductor: R ∝ 1/A.0.5 marks
   9. 9.Derivation: R ∝ l and R ∝ 1/A Combining the two: R ∝ l/A R = ρ (l/A) Here ρ (rho) is a constant of proportionality called the resistivity of the material of the conductor. Its SI unit is Ω m.1 mark

   • Say why the potential difference across R2 equals the one across the 4 Ω resistor: "they are connected in parallel".
   • For R1, subtract both drops from the supply first: "12 − (6 + 4) = 2 V", then use R1 = V / I.
   • Finish the derivation with R = ρ (l/A) and name ρ as the resistivity.

   Marks split as in the board’s published marking scheme

4. Q4Long answer5 marksAsked: 2024

   36. (A) (i) Define electric power. Express it in terms of potential difference (V) and resistance (R). (ii) An electric oven is designed to work on the mains voltage of 220 V. This oven consumes 11 units of electrical energy in 5 hours. Calculate : (a) power rating of the oven (b) current drawn by the oven (c) resistance of the oven when it is red hot OR (B) (i) Write the relation between resistance R and electrical resistivity ρ of the material of a conductor in the shape of cylinder of length l and area of cross-section A. Hence derive the SI unit of electrical resistivity. (ii) The resistance of a metal wire of length 3 m is 60 Ω. If the area of cross-section of the wire is 4x10^-7 m^2, calculate the electrical resistivity of the wire. (iii) State how would electrical resistivity be affected if the wire (of part ‘ii’) is stretched so that its length is doubled. Justify your answer.

   How the model answer begins

   1. (i) Electric power is the rate at which electric energy is dissipated or consumed in an electric circuit. Its SI unit is watt (W).

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5. Q5Long answer5 marksAsked: 2023

   (i) How is electric current related to the potential difference across the terminals of a conductor ? Draw a labelled circuit diagram to verify this relationship. (ii) Why should an ammeter have low resistance ? (iii) Two V - I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows (a) series, (b) parallel combination of the resistors.

6. Q6Long answer5 marksAsked: 2026

   (a) (i) On changing the length and area of cross-section of a conductor, the resistance of the conductor changes, but the resistivity does not change. Why? (ii) The conductors of electric toasters and electric irons are made of alloys rather than pure metals. Why? (iii) Define the SI unit of electric current. or (b) (i) How many bulbs of resistance 8 Ω each, connected in parallel, would draw a current of 2 A from a 4 V battery? (ii) Write the name of the device used for measuring electric current. How is it connected in a circuit? (iii) Write the statement of Joule's law of heating.

7. Q7Long answer5 marksAsked: 2024

   36. (a) (i) The potential difference across the two ends of a circuit component is decreased to one-third of its initial value, while its resistance remains constant. What change will be observed in the current flowing through it ? Name and state the law which helps us to answer this question. (ii) Draw a schematic diagram of a circuit consisting of a battery of four 1.5 V cells, a 5 ohm resistor, a 10 ohm resistor and a 15 ohm resistor and a plug key, all connected in series. Now find (I) the electric current passing through the circuit, and (II) potential difference across the 10 ohm resistor when the plug key is closed. OR (b) (i) When is the potential difference between two points said to be 1 volt ? (ii) A copper wire has a diameter of 0.2 mm and resistivity of 1.6 x 10^-8 ohm m. What will be the length of this wire to make its resistance 14 ohm ? How much does the resistance change, if the diameter of the wire is doubled ?

   How the model answer begins

   1. (a)(i) The current also becomes one-third of its initial value, by Ohm's law. OR (b)(i) The potential difference between two points is 1 volt when 1 joule of work is done in moving 1 coulomb of charge from one to the…

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8. Q8Long answer5 marksAsked: 2023

   (a) State Ohm's Law. (b) Name and define the physical quantity determined by the slope of V – I curve given in the diagram. Use this graph to find the value of this physical quantity in SI units. (c) Establish the relationship between 1 kWh and 1 joule.

   How the model answer begins

   1. Ohm's law: the potential difference V across the ends of a metallic conductor is directly proportional to the current I flowing through it, provided its temperature remains the same; V ∝ I, or V = IR.

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9. Q9Case-based4 marksAsked: 2024

   When electric current flows through a purely resistive circuit, the electric energy is fully converted into heat energy. It is found that the amount of heat produced in the circuit (H) is directly proportional to (i) square of current (I^2), (ii) resistance of the conductor (R) and (iii) time (t) for which current flows through the conductor. In other words, H = I^2Rt. Electrical appliances like electric fuse, electric heater, electric iron, etc., are all based on the heating effect of electric current. (a) Make a list of two characteristics of heating elements. (b) Make a list of two characteristics of electric fuse. (c) Write the name of the law on which an electric fuse works. Explain how the wire of an electric fuse is capable of protecting electric appliances from being damaged due to sudden high electric current. OR (c) The power of an electric heater is 1100 W. If the potential difference across the two ends of this heater is 220 V, find the current flowing through the circuit. What will be the rating of the electric fuse connected in this circuit?

   How the model answer begins

   1. (a) A heating element is made of an alloy such as nichrome. Its resistivity is higher than that of pure metals, so it produces a lot of heat when current flows through it.

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10. Q10Case-based4 marksAsked: 2025

    Study the circuit shown in which two resistors X and Y of resistances 3 ohm and 6 ohm respectively are joined in series with a battery of 2 V. (I) Draw a circuit diagram showing the above two resistors X and Y joined in parallel with same battery and same ammeter and voltmeter. (II) In which combination of resistors will the (i) potential difference across X and Y and (ii) current through X and Y, be the same ? (III) (a) Find the current drawn from the battery by the series combination of the two resistors (X and Y). OR (III) (b) Determine the equivalent resistance of the parallel combination of the two resistors (X and Y).

    How the model answer begins

    1. (I) Circuit diagram of the two resistors X (3 Ω) and Y (6 Ω) joined in parallel: the two resistors are connected between the same two points, so each forms a separate branch. This parallel combination is joined to the 2…

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11. Q11Case-based4 marksAsked: 2024

    39. Study the following circuit : On the basis of this circuit, answer the following questions : (a) Find the value of total resistance between the points A and B. (b) Find the resistance between the points B and C. (c) (i) Calculate the current drawn from the battery, when the key is closed. OR (c) (ii) In the above circuit, the 16 ohm resistor or the parallel combination of two resistors of 8 ohm, which one of the two will have more potential difference across its two ends ? Justify your answer.

    How the model answer begins

    1. (a) The two 8 Ω resistors between A and B are in parallel: 1/R = 1/8 + 1/8 = 1/4, so R_AB = 4 Ω.

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12. Q12Case-based4 marksAsked: 2026

    Read the following passage and answer the questions that follow : Swati, a class 10 student, observes that when she passes close to the refrigerator in her kitchen, she feels the heat, although the things kept inside the refrigerator are cool. (a) Describe the cause of heating in the above-mentioned case. (b) A current I flows through a resistor of resistance R when the potential difference across it is V. Applying Ohm's law, write the formula for amount of heat produced by the resistor in time t. (c) (i) Write any two practical applications of heating effect of electric current. OR (c) (ii) Define the commercial unit of electric energy and express it in Joules (J).

    How the model answer begins

    1. (a) The heating effect of electric current: part of the electrical energy used by the refrigerator becomes heat, and the heat taken out from inside is also released through the coils at the back, so the area nearby…

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13. Q13Long answer4 marksAsked: 2026

    Three students Shweta, Ayesha and Samriddhi were performing an experiment to understand the factors on which the resistance of a conductor depends. Each of them completed an electric circuit with a cell, an ammeter, a plug key and a wire. Shweta inserted a nichrome wire of length 'l' in the circuit, closed the key and took the reading of current in the ammeter. Ayesha inserted a nichrome wire of same thickness but double length '2l' in the circuit, closed the key and took the reading of current in the ammeter. Samriddhi inserted a copper wire of same thickness and length 'l' in the circuit, closed the key and took the reading of current in the ammeter. (a) If the reading of the ammeter with the nichrome wire of length 'l' is X ampere, what will be the reading of the ammeter if the length is doubled while keeping the cross-sectional area of the nichrome wire same? (b) What will be the reading of the ammeter if the cross-sectional area of the nichrome wire is doubled while keeping the length 'l' of the nichrome wire same? (c) Define 'resistivity'. Write its SI unit. Compare the resistivity of alloys with their constituent metals. OR (c) Give reason : (i) Only tungsten is used for making filaments of electric lamps. (ii) Heating elements of bread toasters are made of alloys rather than pure metals.

14. Q14Case-based4 marksAsked: 2025

    In our homes, we receive the supply of electric power through a main supply also called mains, either supported through overhead electric poles or by underground cables. In our country the potential difference between the two wires (live wire and neutral wire) of this supply is 220 V. (a) Write the colours of the insulation covers of the line wires through which supply comes to our homes. (b) What should be the current rating of the electric circuit (220 V) so that an electric iron of 1 kW power rating can be operated ? (c) (i) What is the function of the earth wire ? State the advantage of the earth wire in domestic electric appliances such as electric iron. OR (c) (ii) List two precautions to be taken to avoid electrical accidents. State how these precautions prevent possible damage to the circuit/appliance.

    How the model answer begins

    1. The line wires through which supply comes to our homes have two wires, the live wire and the neutral wire, with a potential difference of 220 V between them. The insulation cover of the live wire is of red colour and…

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15. Q15Case-based4 marksAsked: 2025

    As shown in the diagram, an electric circuit consisting of an ammeter, a voltmeter, 4 cells of 1.5 V each, a plug key with a gap XY was set up. Voltmeter and ammeter readings were recorded in the observation table for four arrangements as given below : Arrangement No. 1 – only resistor R1 in gap XY Arrangement No. 2 – only resistor R2 in gap XY Arrangement No. 3 – Resistors R1 and R2 in series in gap XY Arrangement No. 4 – Resistors R1 and R2 in parallel in gap XY Based on the observations, four V – I graphs A, B, C and D as shown in figure were drawn. Study these graphs. (a) Which one of the graphs represents the series combination of R1 and R2 ? 1 (b) Which one of these graphs represents the parallel combination of R1 and R2 ? 1 (c) (i) Show an arrangement of three resistors, each of resistance 10 Ohm, so that the combination has a resistance of 15 Ohm. Give justification for your answer. 2 OR (c) (ii) A battery of 6 V is connected with a series combination of five resistors of 0.1 Ohm, 0.2 Ohm, 0.3 Ohm, 0.4 Ohm and 0.5 Ohm. How much current would flow through the 0.3 Ohm resistor ? Justify your answer. 2

    How the model answer begins

    1. (a) Graph A: the slope V/I of a V–I graph is the resistance, and the series resistance R₁ + R₂ is the largest, so its line is the steepest.

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16. Q16Case-based4 marksAsked: 2025

    As shown in the diagram, an electric circuit consisting of an ammeter, a voltmeter, 4 cells of 1.5 V each, a plug key with a gap XY was set up. Voltmeter and ammeter readings were recorded in the observation table for four arrangements as given below : Arrangement No. 1 – only resistor R1 in gap XY Arrangement No. 2 – only resistor R2 in gap XY Arrangement No. 3 – Resistors R1 and R2 in series in gap XY Arrangement No. 4 – Resistors R1 and R2 in parallel in gap XY Based on the observations, four V – I graphs A, B, C and D as shown in figure were drawn. Study these graphs. (a) Which one of the graphs represents the series combination of R1 and R2 ? (b) Which one of these graphs represents the parallel combination of R1 and R2 ? (c) (i) Show an arrangement of three resistors, each of resistance 10 Ω, so that the combination has a resistance of 15 Ω. Give justification for your answer. OR (c) (ii) A battery of 6 V is connected with a series combination of five resistors of 0.1 Ω, 0.2 Ω, 0.3 Ω, 0.4 Ω and 0.5 Ω. How much current would flow through the 0.3 Ω resistor ? Justify your answer.

    How the model answer begins

    1. (a) Graph A: the series resistance R₁ + R₂ is the greatest, and the slope V/I of a V–I graph is the resistance, so the series line is the steepest.

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17. Q17Case-based4 marksAsked: 2024

    In a domestic circuit five LED bulbs are arranged as shown. The source voltage is 220 V and the power rating of each bulb is marked in the circuit diagram. Based on the following circuit diagram, answer the following questions : (a) State what happens when (i) key K1 is closed. (ii) key K2 is closed. 1 (b) Find the current drawn by the bulb B when it glows. 1 (c) Calculate 2 (i) the resistance of bulb B, and (ii) total resistance of the combination of four bulbs B, C, D and E. OR (c) What would happen to the glow of all the bulbs in the circuit when keys K1 and K2 both are closed and the bulb C suddenly get fused ? Give reason to justify your answer. 2

    How the model answer begins

    1. (a)(i) When K₁ is closed, only bulb A glows.

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18. Q18Case-based4 marksAsked: 2023

    39. Consider the following electrical circuit diagram in which nine identical resistors of 3 ohm each are connected as shown. If the reading of the ammeter A1 is 1 ampere, answer the following questions : (a) What is the relationship between the readings of A1 and A3 ? Give reasons for your answer. (b) What is the relationship between the readings of A2 and A3 ? (c) Determine the reading of the voltmeter V1. OR (c) Find the total resistance of the circuit.

    How the model answer begins

    1. (a) Ammeters A1 and A3 show the same reading, A1 = A3. A1 reads 1 A, so A3 also reads 1 A.

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19. Q19Short answer3 marksAsked: 2026

    (a) Name a device which is used to : (i) Maintain a constant potential difference in a circuit. (ii) Change the electric current in an electric circuit. (b) When the potential difference between the terminals of an electric heater is 110 V, a current of 5 A flows through it. What will be the value of current flowing through it when the potential difference is increased to 220 V ?

20. Q20Short answer3 marksAsked: 2026

    Consider the given electric circuit : Calculate the following : (a) Total resistance of the circuit (b) The electric current drawn from the battery (c) Potential difference between points P and Q

40 more questions of this chapter, each with its model answer, in the Ask Medha app.

Objective questions with the board’s key (10)

1. 1. CBSE 2026

   The correct arrangement to connect ammeter and voltmeter in an electric circuit is :

   • (A) Ammeter in parallel and voltmeter in series
   • (B) Both ammeter and voltmeter in parallel
   • (C) Ammeter in series and voltmeter in parallel ✓
   • (D) Both ammeter and voltmeter in series

   Answer: (C)

2. 2. CBSE 2026

   In which situation/situations will the bulb glow assuming all other connections in the electric circuit are complete and functional ?

   • (A) Only situation (i)
   • (B) Only situation (ii)
   • (C) Situation (ii) and (iii)
   • (D) Only situation (iii) ✓

   Answer: (D)

3. 3. CBSE 2026

   In an electric circuit carrying current I, a 2 ohm resistor is replaced by an 8 ohm resistor without changing the connected (ideal) battery. Then :

   • (A) current becomes I/4 and potential difference V/4
   • (B) current becomes I/4 and potential difference remains V ✓
   • (C) current becomes 4I and potential difference remains V
   • (D) current becomes 4I and potential difference V/4

   Answer: (B)

4. 4. CBSE 2025

   A piece of wire of resistance 'R' is cut lengthwise into three identical parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R', then the value of R/R' is :

   • (A) 1/9
   • (B) 1/3
   • (C) 3
   • (D) 9 ✓

   Answer: (D)

5. 5. CBSE 2025

   An electric bulb is rated 220 V; 11W. The resistance of its filament when it glows with a power supply of 220 V is :

   • (A) 4400 ohm ✓
   • (B) 440 ohm
   • (C) 400 ohm
   • (D) 20 ohm

   Answer: (A)

6. 6. CBSE 2025

   The minimum number of identical bulbs of rating 4V; 6W, that can work safely with desired brightness, when connected in series with a 240 V mains supply is :

   • (A) 20
   • (B) 40
   • (C) 60 ✓
   • (D) 80

   Answer: (C)

7. 7. CBSE 2025

   Assertion (A) : In the common domestic circuits the earth wire is connected to a metallic plate buried deep inside the earth. Reason (R) : Earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, so the user may not get a severe electric shock.

   • (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). ✓
   • (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
   • (C) Assertion (A) is true, but Reason (R) is false.
   • (D) Assertion (A) is false, but Reason (R) is true.

   Answer: (A)

8. 8. CBSE 2025

   Four identical resistors of 12 Ω each are connected in series to form a square ABCD as shown in the figure. The resistance of the network between the two points 1 and 2 is :

   • (A) 48 Ω
   • (B) 36 Ω
   • (C) 9 Ω ✓
   • (D) 6 Ω

   Answer: (C)

9. 9. CBSE 2025

   An electric bulb is connected to a power supply of 220 V. If the current drawn by the bulb from the supply is 500 mA, the power of the bulb is :

   • (A) 11 W
   • (B) 110 W ✓
   • (C) 220 W
   • (D) 1100 W

   Answer: (B)

10. 10. CBSE 2025

    Assertion (A) : Nichrome is an alloy which is commonly used in electrical heating devices such as electric irons, toasters, etc. Reason (R) : The resistivity of nichrome is high and its resistance decreases with increase in temperature.

    • (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
    • (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    • (C) Assertion (A) is true, but Reason (R) is false. ✓
    • (D) Assertion (A) is false, but Reason (R) is true.

    Answer: (C)

Questions parents and students ask

How many marks does "Electricity" carry in CBSE Class 10 Science?

In the CBSE papers of 2023–2026, this chapter carried about 8 marks and about 3 questions a year; by marks it ranks 2 in Science.

Which are the most important (VVI) questions of "Electricity"?

The 20 questions above are from the board’s real papers, each with the years it was asked; the most-asked come first with their full model answers. All 60 written questions of this chapter, with answers, are in the Ask Medha app.

Do the answers follow the board’s marking scheme?

Yes. CBSE publishes its marking schemes; every model answer here is written point by point to the marks the board’s own scheme gives, and checked by a second, independent model.