Chapter 12: Electricity

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

1. Q1Short answer2 marksAsked: 2021, 2024

   Draw a labelled diagram of electric bulb.

   

   Medha Ma’am

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   Model answer · labelled diagram, electric bulb

   1. 1.The labelled diagram of an electric bulb is drawn below showing its main parts.1 mark
   2. 2.The electric bulb consists of a glass bulb enclosing a filament made of tungsten, which is connected to two terminals through a base contact that fits into the socket for making the circuit connection.1 mark

   Diagram: Draw an electric bulb showing: the glass bulb (outer glass covering), the filament (tungsten) inside, the two terminals/lead wires connecting the filament, and the base contact (metal base) at the bottom through which the terminals pass.

   • Draw a clear outline of the glass bulb and mark the filament inside it with a label.
   • Label the base contact and the terminals where the connecting wires attach.
   • Write 'tungsten' next to the filament since the book states tungsten is used for filaments.

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

2. Q2Short answer2 marksAsked: 2021, 2026

   Define the strength of electric current.

   

   Medha Ma’am

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   Model answer · definition, electric current

   1. 1.The strength of electric current is the amount of charge flowing through a particular area, that is, through a cross-section of a conductor, in unit time.1 mark
   2. 2.If a net charge Q flows across any cross-section of a conductor in time t, then the current I through the cross-section is I = Q/t.1 mark

   • Begin the first line with 'The strength of electric current is the amount of charge...' using these exact words.
   • Write the formula I = Q/t clearly as a separate line.
   • Do not add the unit ampere or ammeter details since the question only asks for the definition.

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

3. Q3Long answer6 marksAsked: 2021

   What is parallel combination of resistances ? Find the expression for equivalent resistance of parallel combination of resistances R1, R2 and R3.

   

   Medha Ma’am

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   Hear it from Medha Ma’am · 135 s

   Model answer · parallel combination of resistances

   1. 1.When two or more resistors are connected such that the potential difference across each resistor is the same, it is called parallel combination. Three resistors R1, R2 and R3 are joined in parallel between two points X and Y, and this combination is connected to a battery, a plug key and an ammeter.1 mark
   2. 2.Let I be the total current flowing in the circuit, as given by the ammeter, and let V be the potential difference across the combination, which is also the potential difference across each of the resistors R1, R2 and R3. It is observed that the total current I is equal to the sum of the separate currents through each branch of the combination, that is, I = I1 + I2 + I3, where I1, I2 and I3 are the currents flowing through R1, R2 and R3 respectively.1 mark
   3. 3.According to Ohm's law, applied to each resistor separately, since the potential difference V across each resistor is the same, the current through each resistor is I1 = V/R1, I2 = V/R2, and I3 = V/R3.1 mark
   4. 4.Let Rp be the equivalent resistance of the parallel combination of resistors. By applying Ohm's law to the parallel combination of resistors, the total current is given by I = V/Rp.1 mark
   5. 5.Substituting the values of I, I1, I2 and I3 from the above equations, we get V/Rp = V/R1 + V/R2 + V/R31 mark
   6. 6.Dividing out V from both sides, the expression obtained is 1/Rp = 1/R1 + 1/R2 + 1/R3 Thus, the reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistances.1 mark

   Diagram: Draw three resistors R1, R2 and R3 connected in parallel between two common points X and Y, with the combination connected to a battery, a plug key and an ammeter in series, and label the currents I1, I2, I3 through each resistor and the total current I and potential difference V across the combination.

   • Write the line 'I = I1 + I2 + I3' as the total current step.
   • Write Ohm's law applied individually as I1 = V/R1, I2 = V/R2, I3 = V/R3.
   • End with the final expression 1/Rp = 1/R1 + 1/R2 + 1/R3.

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

4. Q4Long answer6 marksAsked: 2024

   Explain conductor, insulator and semiconductor with examples.

   How the model answer begins

   1. Materials through which electric charge flows easily are called conductors. A component of a given size that offers a low resistance is a good conductor, because the electrons within it are only slightly restrained by…

   The full answer from Medha Ma’am →
5. Q5Long answer6 marksAsked: 2022

   Find the potential difference between the ends of a resistor of 4 ohm if 100 joule of heat is being generated per second.

   How the model answer begins

   1. Resistance of the resistor R = 4 ohm and the heat generated H = 100 joules per second are given. Since heat is produced at the rate of 100 joules per second, the power P associated with this heating is 100 watt (because…

   The full answer from Medha Ma’am →
6. Q6Long answer6 marksAsked: 2021

   Find expression for equivalent resistance of three different resistances combined in series.

   How the model answer begins

   1. Three resistors having resistances R1, R2 and R3 are joined end to end, that is, connected in series, with a battery of potential difference V.

   The full answer from Medha Ma’am →
7. Q7Short answer2 marksAsked: 2021

   If the resistance of any electric bulb filament is 1200 ohm, how much electric current is required from source of 220 V ?

   How the model answer begins

   1. Given: resistance of the bulb filament R = 1200 Ω, potential difference V = 220 V. According to Ohm's law, R = V/I, so the formula for electric current is I = V/R. I = 220/1200

   The full answer from Medha Ma’am →
8. Q8Short answer2 marksAsked: 2021

   Write three main properties of fuse wire.

   How the model answer begins

   1. The fuse wire has a very low melting point, so when an unduly high electric current flows through the circuit, the temperature of the fuse wire increases and it melts quickly, breaking the circuit.

   The full answer from Medha Ma’am →
9. Q9Short answer2 marksAsked: 2024

   What do you understand by 'short-circuit' ?

   How the model answer begins

   1. When the live wire and the neutral wire come into direct contact in an electric circuit, the resistance of the circuit becomes very low.

   The full answer from Medha Ma’am →
10. Q10Short answer2 marksAsked: 2024

    How is the resistance of a wire affected by its area of cross-section ?

    How the model answer begins

    1. The resistance of a uniform metallic conductor is inversely proportional to the area of cross-section (A) of the conductor, that is, R ∝ 1/A.

    The full answer from Medha Ma’am →
11. Q11Short answer2 marksAsked: 2025

    Why is inert gas filled in electric bulb?

    How the model answer begins

    1. Inert gas is filled in the electric bulb to protect the tungsten filament from oxidation. When the filament is heated to a very high temperature, it would react with the oxygen present in air and get oxidised and burnt.…

    The full answer from Medha Ma’am →
12. Q12Short answer2 marksAsked: 2025

    What do you understand by potential difference?

    How the model answer begins

    1. The work done to move a unit positive charge from one point to another in an electric circuit is called the potential difference between those two points.

    The full answer from Medha Ma’am →
13. Q13Short answer2 marksAsked: 2025

    What is electric current? Write its equation and unit.

    How the model answer begins

    1. Electric current is the rate of flow of electric charge through a conductor.

    The full answer from Medha Ma’am →
14. Q14Short answer2 marksAsked: 2026

    Why is fuse wire used in electrical circuit ?

    How the model answer begins

    1. A fuse wire is used in an electrical circuit because it protects circuits and appliances by stopping the flow of any unduly high electric current. The fuse is placed in series with the device, so if a current larger…

    The full answer from Medha Ma’am →
15. Q15Short answer2 marksAsked: 2026

    What is the combination of resistance ? How many types of it are there ?

    How the model answer begins

    1. The combination of resistors is the process of connecting two or more resistors together in an electric circuit. Such a combination of resistors can be replaced by an equivalent single resistor so that the potential…

    The full answer from Medha Ma’am →
16. Q16Short answer2 marksAsked: 2026

    What is resistance ? Write its SI unit.

    How the model answer begins

    1. Resistance is the property of a conductor to resist the flow of charges through it.

    The full answer from Medha Ma’am →
17. Q17Short answer2 marksAsked: 2023

    On which factors does the resistance of a conductor depend ?

    How the model answer begins

    1. The resistance of a conductor is directly proportional to its length (l), that is, R ∝ l.

    The full answer from Medha Ma’am →
18. Q18Short answer2 marksAsked: 2023

    Define electric potential and write its S.I. unit.

    How the model answer begins

    1. Electric potential at a point is defined as the work done in bringing a unit positive charge from infinity to that point.

    The full answer from Medha Ma’am →
19. Q19Short answer2 marksAsked: 2022

    An electric bulb for domestic use is marked 220 V, 60 W. What will you interpret from this ?

    How the model answer begins

    1. 220 V means that the bulb is designed to operate at a potential difference of 220 volts. This is the potential difference that must be applied across the bulb so that it works normally and gives its rated output.

    The full answer from Medha Ma’am →
20. Q20Short answer2 marksAsked: 2022

    Define electric potential and write its SI unit.

    How the model answer begins

    1. The electric potential at a point is the work done in bringing a unit positive charge from infinity to that point.

    The full answer from Medha Ma’am →

5 more questions of this chapter, each with its model answer, in the AskMedha app.

Objective questions with the board’s key (10)

1. 1. Bihar Board 2026

   The mathematical form of Ohm's law is

   • (A) I = VR
   • (B) I = V/R ✓
   • (C) I = R/V
   • (D) I = V + R

   Answer: (B)

2. 2. Bihar Board 2026

   Electrons are released in electrolysis at the

   • (A) Anode ✓
   • (B) Cathode
   • (C) Both (A) and (B)
   • (D) None of these

   Answer: (A)

3. 3. Bihar Board 2026

   What will be the effect on the resistance of the conductor due to increase in temperature ?

   • (A) Increases ✓
   • (B) Decreases
   • (C) Does not increase or decrease
   • (D) None of these

   Answer: (A)

4. 4. Bihar Board 2026

   In a dry cell the negative electrode is made of

   • (A) Brass
   • (B) Carbon
   • (C) Zinc ✓
   • (D) None of these

   Answer: (C)

5. 5. Bihar Board 2026

   Which of the following is a safety device ?

   • (A) Ammeter
   • (B) Unit Board
   • (C) MCB ✓
   • (D) None of these

   Answer: (C)

6. 6. Bihar Board 2026

   The electricity supplied to our houses is

   • (A) Direct current at 220 V
   • (B) Direct current at 12 V
   • (C) Alternating current at 220 V ✓
   • (D) Alternating current at 12 V

   Answer: (C)

7. 7. Bihar Board 2026

   The SI unit of electric power is

   • (A) volt
   • (B) watt ✓
   • (C) joule
   • (D) coulomb

   Answer: (B)

8. 8. Bihar Board 2026

   Which of the following combinations increases the value of resistance?

   • (A) Series ✓
   • (B) Parallel
   • (C) Both (A) and (B)
   • (D) None of these

   Answer: (A)

9. 9. Bihar Board 2026

   The charge carriers in metal are

   • (A) Electrons ✓
   • (B) Protons
   • (C) Neutrons
   • (D) None of these

   Answer: (A)

10. 10. Bihar Board 2026

    What kind of conductor is pure water ?

    • (A) Conductor
    • (B) Bad conductor ✓
    • (C) Super conductor
    • (D) None of these

    Answer: (B)

Questions parents and students ask

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

In the Bihar Board papers of 2021–2026, this chapter carried about 7 marks and about 9 questions a year; by marks it ranks 3 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 25 written questions of this chapter, with answers, are in the AskMedha app.

Do the answers follow the board’s marking scheme?

BSEB does not publish a marking scheme. Each answer is written point by point on a structure derived from past papers and checked by a second, independent model; it is never called the board’s official scheme.