⚡ CBSE · Class 10 · Science · Chapter 12

Chapter 12:
Electricity

Complete chapter resources for CBSE Class 10 Science — topic breakdown, key formulas, sample questions, previous year board questions, and instant AI question paper generation.

5Topics
6–8Board marks
8Sample questions
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Key Formulas — Chapter 12
  • Ohm's law: V = IR
  • Resistance: R = ρL / A
  • Series: Rs = R1 + R2 + R3
  • Parallel: 1/Rp = 1/R1 + 1/R2 + 1/R3
  • Power: P = VI = I²R = V²/R
  • Joule's law: H = I²Rt
Chapter Overview

What this chapter covers

Chapter 12 of NCERT Class 10 Science introduces the fundamental concepts of electric current, potential difference, and resistance. Electric current is defined as the rate of flow of charge (I = Q/t, measured in amperes), while potential difference is the work done per unit charge between two points in a circuit (V = W/Q, measured in volts). Ohm's law (V = IR) establishes the linear relationship between these quantities for metallic conductors at constant temperature, forming the cornerstone of all circuit analysis in this chapter.

The chapter then extends to resistivity — the intrinsic property of a material given by R = ρL/A — and the combination of resistors in series and parallel circuits. In series, the same current flows through all components and total resistance adds up; in parallel, the same voltage appears across all branches and total resistance is less than the smallest individual resistor. These two configurations are tested extensively in board numericals and circuit diagram questions.

The final part covers Joule's law of heating (H = I²Rt) and electric power (P = VI), which explain why high-resistance appliances like heaters and filament bulbs generate heat and why domestic wiring uses parallel connections. Board questions on this section include cost-of-electricity calculations (using Energy = Pt and 1 kWh = 3.6 × 10⁶ J) and reasoning about safe domestic circuit design.

Topics

What's inside Chapter 12

As per NCERT Class 10 Science (CBSE syllabus)

Topic 1
Electric Current & Potential Difference
Definition of electric current (I = Q/t), SI units, conventional current direction. Potential difference as work done per unit charge (V = W/Q). Role of a cell or battery in maintaining a potential difference.
Topic 2
Ohm's Law & Resistance
Statement and mathematical form V = IR. Graphical verification: V–I graph is a straight line whose slope gives resistance. Factors affecting resistance: length, cross-sectional area, material (resistivity ρ), and temperature.
Topic 3
Resistors in Series & Parallel
Derivation of equivalent resistance for series (Rs = R1 + R2 + …) and parallel (1/Rp = 1/R1 + 1/R2 + …) combinations. Comparison of current, voltage, and total resistance in both configurations. Practical applications in domestic circuits.
Topic 4
Heating Effect of Electric Current
Joule's law: H = I²Rt. Derivation from work-energy considerations. Applications in electric heaters, filament bulbs, and fuses. Why fuse wire must have high resistivity and low melting point.
Topic 5
Electric Power & Energy
Power P = VI = I²R = V²/R (measured in watts). Electrical energy consumed E = Pt. Commercial unit: 1 kilowatt-hour (kWh) = 3.6 × 10⁶ J. Calculating electricity bills; why high-power appliances draw large current.
Connections

How this chapter fits in

Useful for setting question difficulty and cross-chapter papers.

Builds on
Class 8 · Chemical Effects of Current
Conductors, insulators, and basic circuit concepts introduced earlier
Class 9 · Work & Energy
Energy transfer and work-energy theorem underpin Joule's heating law
Chapter 12 Electricity
Leads to
Ch 13 · Magnetic Effects of Current
Oersted's experiment, electromagnets, and motors use current from this chapter
Class 12 · Current Electricity
Kirchhoff's laws, Wheatstone bridge, and EMF build directly on these foundations
Board Blueprint

Marks & question-type breakdown

Typical pattern based on CBSE Class 10 Science board papers from the last five years.

Question type Marks Typical count What's usually tested
MCQ / Objective 1 1–2 Identify Ohm's law form, units of resistance, or nature of V–I graph
Very Short Answer 2 1 State Ohm's law, define resistivity, or compare series vs parallel resistance
Short Answer / Numerical 3 1 Calculate equivalent resistance, current in a branch, or heat produced in a wire
Long Answer / Circuit Diagram 4–5 1 Draw and analyse a combined series-parallel circuit; cost-of-electricity word problem
Total (approximate) 6–8 4–5 Weightage varies across paper sets and years
Sample Questions

8 sample questions — generated by MarksZen AI

Aligned to CBSE Class 10 Science Chapter 12. Covers all question types across Easy, Medium, and Hard difficulty.

Q1 Easy 1 mark MCQ
The SI unit of electric resistance is: (a) Ampere (b) Volt (c) Ohm (d) Watt
Q2 Easy 2 marks Short Answer
State Ohm's law. A resistor has a potential difference of 6 V across it and a current of 0.5 A flows through it. Calculate the resistance of the resistor.
Q3 Medium 2 marks Short Answer
Two resistors of 6 Ω and 12 Ω are connected in parallel. Calculate the equivalent resistance of the combination. How does this compare with the smaller individual resistance?
Q4 Medium 3 marks Numerical
Three resistors of 3 Ω, 6 Ω, and 9 Ω are connected in series to a battery of 18 V. (i) Find the equivalent resistance of the circuit. (ii) Find the current flowing through the circuit. (iii) Find the potential difference across the 6 Ω resistor.
Q5 Medium 3 marks Short Answer
Explain why: (i) Tungsten is used as the filament in electric bulbs. (ii) Copper and aluminium wires are used for transmission of electricity. (iii) Series arrangement is not used for domestic circuits.
Q6 Hard 4 marks Numerical
An electric iron of resistance 40 Ω draws a current of 5 A. (i) Calculate the power consumed by the iron. (ii) Calculate the heat produced in 2 minutes. (iii) If the electricity tariff is ₹6 per kWh, find the cost of using the iron for 3 hours. (iv) State Joule's law of heating.
Q7 Hard 5 marks Circuit Diagram
Draw a circuit diagram showing three resistors R1 = 4 Ω, R2 = 6 Ω, and R3 = 12 Ω connected such that R2 and R3 are in parallel, and this combination is in series with R1. The battery has an EMF of 8 V. (i) Calculate the equivalent resistance of the entire circuit. (ii) Find the total current drawn from the battery. (iii) Find the current through R2 and R3 separately.
Q8 Hard 5 marks Word Problem
A household uses the following electrical appliances daily: one 60 W bulb for 5 hours, one 1000 W heater for 2 hours, and one 80 W fan for 10 hours. (i) Calculate the total electrical energy consumed per day in kWh. (ii) Calculate the monthly electricity bill (30 days) at ₹5 per kWh. (iii) The heater element has a resistance of 40 Ω. What current does it draw from a 200 V supply?
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Previous Year Questions

From CBSE board examinations

Actual questions from past Class 10 Science board papers — Electricity chapter.

Board 20223 marks
Three resistors R1, R2, and R3 are connected in parallel. Derive the expression for the equivalent resistance of the combination. State one advantage of connecting electrical appliances in parallel in a domestic circuit. (All India 2022)
Board 20232 marks
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances together? (CBSE 2023)
Board 20205 marks
(a) State Ohm's law. Draw a circuit diagram to verify Ohm's law. (b) A wire of resistivity ρ has length L and area of cross-section A. What will be the resistance of another wire of the same material with length 2L and area of cross-section A/2? (c) Calculate the cost of electricity consumed by a 1500 W geyser used for 2 hours per day for 30 days, at ₹4 per kWh. (Delhi 2020)
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FAQ

Questions teachers ask

How many marks does Electricity carry in the CBSE Class 10 Science board exam? +
Electricity typically carries 6–8 marks in the CBSE Class 10 Science board exam, spread across 3–4 questions — usually one 1-mark MCQ, one 2-mark short answer on formulas or circuit calculations, and one 3–5 mark numerical or circuit diagram question. The chapter has featured in every CBSE Class 10 Science board paper for the last decade.
What is Ohm's law and how is it tested in CBSE board exams? +
Ohm's law states that the current (I) through a conductor is directly proportional to the potential difference (V) across it at constant temperature: V = IR, where R is the resistance in ohms. Board exams test it through 1-mark definition questions, 2-mark numerical problems asking students to calculate V, I, or R, and graph-based questions where the slope of a V–I graph equals resistance.
What is the difference between series and parallel circuits, and which formulas must students know? +
In a series circuit, components are connected end-to-end; current is the same through all components and total resistance Rs = R1 + R2 + R3. In a parallel circuit, components share the same two terminals; voltage is the same across all components and 1/Rp = 1/R1 + 1/R2 + 1/R3. Board questions frequently ask students to compare total resistance or current in both configurations, and to draw the circuit diagrams.
How is Joule's law of heating tested in CBSE Class 10 Science exams? +
Joule's law states that the heat produced in a conductor is H = I²Rt, where I is current, R is resistance, and t is time. It is also written as H = VIt or H = V²t/R. Board questions cover 2-mark calculations of heat or electrical energy consumed, the basis for why high-resistance conductors are used in heaters and bulb filaments, and cost-of-electricity word problems using P = VI.
How do I generate a custom question paper for Electricity (Class 10 Science) using MarksZen? +
Sign up for a free MarksZen account, choose CBSE Class 10 Science, select Chapter 12 (Electricity), set your preferred question-type mix (MCQ, short answer, numerical, circuit diagram) and total marks — the AI generates a complete board-aligned paper with answer key in under 2 minutes, ready for PDF export.