NCERT Class 10 Science Chapter 11 – Electricity

NCERT Class 10 Science Chapter 11 explains the fundamental concepts of electric current and its effects in circuits. In NCERT Class 10 Science Chapter 11, students study electric current, potential difference, Ohm’s law, resistance, heating effect and electric power. NCERT Class 10 Science Chapter 11 is one of the most important physics chapters for CBSE board exams because it includes both theory and numerical problems.

NCERT Class 10 Science Chapter 11 begins with Electric Current, defined as the flow of electric charge. Electric current is denoted by I and measured in Ampere (A). According to NCERT Class 10 Science Chapter 11,
1 Ampere = 1 Coulomb/second (1 A = 1 C/s).

The chapter then explains Electric Potential and Potential Difference. Potential difference is given by: V = W/Q
The SI unit is Volt (V), where 1 V = 1 J/C.

A key concept in NCERT Class 10 Science Chapter 11 is Ohm’s Law, which states that at constant temperature: V = IR
Here, R is the resistance measured in Ohm (Ω). The V–I graph for a metallic conductor is a straight line passing through the origin.

NCERT Class 10 Science Chapter 11 also discusses factors affecting resistance. Resistance depends on:

• Length of conductor
• Area of cross-section
• Nature of material (Resistivity ρ). The formula given in NCERT Class 10 Science Chapter 11 is: R = ρl/A, Unit of resistivity: Ω m.

Another important section of NCERT Class 10 Science Chapter 11 is the Combination of Resistors:

Resistors in Series: R = R₁ + R₂ + R₃

Resistors in Parallel: 1/R = 1/R₁ + 1/R₂ + 1/R₃

NCERT Class 10 Science Chapter 11 explains the Heating Effect of Electric Current, based on Joule’s Law of Heating: H = I²Rt

The final topic in NCERT Class 10 Science Chapter 11 is Electric Power, defined as: P = VI
Other forms:
P = I²R and P = V²/R
Unit of power: Watt (W)
Electrical energy unit: 1 kWh = 3.6 × 10⁶ J

NCERT Class 10 Science Chapter 11 is highly important for CBSE board exams because numerical problems based on Ohm’s law, resistance combination and electric power are frequently asked.

Students should refer to the official NCERT website at for authentic textbooks and syllabus updates.

For structured preparation of NCERT Class 9–12 for UPSC, BPSC and State PCS examinations, strengthen your basics with our complete NCERT Book Notes PDF for Class 9-12, available inside the NCERT foundation course level-2.

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11.1 Electric current and circuit

• An Electric Current is the flow of electric charge through a conductor.
• In metallic conductors, electric current is due to the flow of Electrons.
• The direction of conventional current is taken opposite to the direction of flow of electrons.
• Electric current is denoted by I and its SI unit is Ampere (A).
• One Ampere is defined as the flow of one coulomb of charge per second, that is 1 A = 1 C/s.
• An electric current in a circuit is measured using an Ammeter, which is connected in series.
• An Electric Circuit is a closed conducting path through which electric current flows.
• A circuit consists of components such as Cell, Battery, Switch, Bulb and Connecting Wires.

11.2 Electric potential and potential difference

• Electric Potential at a point is the work done to bring a unit positive charge from infinity to that point in an electric field.
• Potential Difference (V) between two points is the work done to move a unit charge from one point to another.
• Mathematically, V = W/Q, where W is work done and Q is charge.
• The SI unit of potential difference is Volt (V).
• One Volt is the potential difference when one joule of work is done to move one coulomb of charge, that is 1 V = 1 J/C.
• Potential difference across a conductor is measured using a Voltmeter, which is connected in parallel.
• A source such as a Cell or Battery maintains a potential difference in a circuit.
• Electric current flows in a circuit due to the presence of potential difference.

11.3 Circuit diagram

• A Circuit Diagram is a graphical representation of an electric circuit using standard Electrical Symbols.
• Components such as Cell, Battery, Bulb, Switch, Ammeter, Voltmeter and Resistor are represented by conventional symbols.
• A Closed Switch allows current to flow, while an Open Switch breaks the circuit and stops the flow of current.
• An Ammeter is always connected in Series, and a Voltmeter is connected in Parallel across the component.
• A circuit must form a Closed Loop for current to flow continuously.
• Circuit diagrams simplify complex circuits and make analysis easier.
• Correct representation ensures proper understanding of connections and measurement points.

11.4 Ohm’s law

• Ohm’s Law states that at constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
• Mathematically, V ∝ I, which gives V = IR, where R is the resistance of the conductor.
• The constant of proportionality R is called the Resistance of the conductor.
• The SI unit of resistance is Ohm (Ω).
• One Ohm is the resistance when a current of 1 ampere flows through a conductor under a potential difference of 1 volt, that is 1 Ω = 1 V/A.
• A graph between V and I for a metallic conductor at constant temperature is a Straight Line passing through the origin.
• The slope of the V–I graph represents the Resistance of the conductor.

11.5 Factors on which the resistance of a conductor depends

• The resistance of a conductor depends on its Length (l); resistance is directly proportional to length, that is R ∝ l.
• It depends on the Area of Cross-section (A); resistance is inversely proportional to area, that is R ∝ 1/A.
• It depends on the Nature of Material, represented by a constant called Resistivity (ρ).
• It also depends on the Temperature of the conductor; for metallic conductors, resistance increases with rise in temperature.
• Combining the factors, the resistance of a conductor is given by R = ρ l / A.
• The SI unit of resistivity is Ohm metre (Ω m).
• Materials with low resistivity, such as Copper and Aluminium, are good conductors.

11.6 Resistance of a system of resistors

• In an electric circuit, two or more resistors can be connected in different combinations to obtain a required Effective Resistance.
• The total resistance of a system depends on whether resistors are connected in Series or in Parallel.
• In a Series Combination, resistors are connected end to end so that the same current flows through each resistor.
• In a Parallel Combination, resistors are connected across the same two points, so the potential difference across each resistor is the same.
• The arrangement of resistors affects the total current, potential difference and overall resistance of the circuit.
• Calculating effective resistance helps in designing circuits for practical applications.
• Two important cases are studied: Resistors in Series and Resistors in Parallel.

11.6.1 Resistors in Series

• In a Series Combination, resistors are connected one after another such that the same Current (I) flows through each resistor.
• The total Potential Difference (V) across the combination is equal to the sum of potential differences across individual resistors.
• If resistors R₁, R₂, R₃ are connected in series, the effective resistance R is given by:
  R = R₁ + R₂ + R₃.
• The effective resistance in series is always Greater than the largest individual resistance.
• Series combination is used when a higher resistance is required in a circuit.
• If one resistor in series fails, the entire circuit breaks and current stops flowing.
• Series circuits are commonly used in simple electric devices.

11.6.2 Resistors in Parallel

• In a Parallel Combination, resistors are connected across the same two points so that the Potential Difference (V) across each resistor is the same.
• The total current flowing in the circuit is equal to the sum of currents through individual resistors.
• If resistors R₁, R₂, R₃ are connected in parallel, the effective resistance R is given by:
  1/R = 1/R₁ + 1/R₂ + 1/R₃.
• The effective resistance in parallel is always Less than the smallest individual resistance.
• Parallel combination is used in household wiring to ensure the same voltage across all appliances.
• If one resistor fails in parallel, the other resistors continue to function.
• Parallel circuits provide independent functioning of electrical devices.

11.7 Heating effect of electric current

• When an electric current passes through a conductor, electrical energy is converted into Heat Energy; this is called the Heating Effect of Electric Current.
• The heat produced in a conductor depends on the Current (I), Resistance (R) and Time (t) for which the current flows.
• According to Joule’s Law of Heating, the heat produced is given by:
  H = I²Rt.
• Heat produced is directly proportional to the square of current, resistance and time.
• This effect is used in devices such as Electric Heaters, Irons and Kettles.
• Excessive heating in circuits can cause damage, so devices like Fuses are used for protection.
• A fuse wire has Low Melting Point and melts when current exceeds safe limit, breaking the circuit.

11.8 Electric power

• Electric Power (P) is the rate at which electrical energy is consumed or work is done in a circuit.
• It is given by the formula: P = V × I, where V is potential difference and I is current.
• Using Ohm’s law, electric power can also be expressed as P = I²R and P = V²/R.
• The SI unit of electric power is Watt (W).
• One Watt is the power consumed when one ampere of current flows under a potential difference of one volt, that is 1 W = 1 V × 1 A.
• A larger unit of power is Kilowatt (kW), where 1 kW = 1000 W.
• Electrical energy consumed is measured in Kilowatt-hour (kWh), commonly called one Unit of electricity.
• 1 kWh = 3.6 × 10⁶ Joules, which represents the energy consumed by a 1000 W device in one hour.

Exam Oriented Facts

• Electric Current (I) is the flow of electric charge.
• SI unit: Ampere (A).
• 1 A = 1 C/s (1 coulomb per second).
• Current is measured using an Ammeter (connected in series).
• A circuit must be Closed for current to flow.
• Potential Difference (V) = W/Q.
• SI unit: Volt (V).
• 1 V = 1 J/C.
• Measured using a Voltmeter (connected in parallel).
• A Cell/Battery maintains potential difference in a circuit.
• At constant temperature: V ∝ I.
• Mathematical form: V = IR.
• SI unit of resistance: Ohm (Ω).
• 1 Ω = 1 V/A.
• V–I graph for metallic conductor → Straight Line through origin.
• R ∝ l (directly proportional to length).
• R ∝ 1/A (inversely proportional to area).
• Formula: R = ρl/A.
• ρ (Resistivity) depends on material.
• SI unit of resistivity: Ω m.
• Good conductors: Copper, Aluminium.
• Effective resistance: R = R₁ + R₂ + R₃.
• Current same through each resistor.
• Total resistance increases.
• Effective resistance: 1/R = 1/R₁ + 1/R₂ + 1/R₃.
• Potential difference same across each resistor.
• Effective resistance is less than smallest resistor.
• Used in Household Wiring.
• Joule’s Law of Heating: H = I²Rt.
• Heat ∝ square of current.
• Used in Heaters, Iron, Kettle.
• Fuse protects circuit; made of low melting point material.
• Heating element material: Nichrome.
• P = VI.
• Also: P = I²R and P = V²/R.
• SI unit: Watt (W).
• 1 kW = 1000 W.
• Electrical energy unit: kWh.
• 1 kWh = 3.6 × 10⁶ J.

NCERT Class 10 Science Chapter 11 – Electricity builds a strong foundation in electric circuits and problem-solving skills. Mastering NCERT Class 10 Science Chapter 11 ensures clarity in formulas, derivations and numerical applications.

NCERT Class 10 Science Chapter 11 is a high-weightage chapter in CBSE exams and forms the base for advanced electrical concepts in higher classes.

Continue reading NCERT Class 10 Science Chapter 12 – Magnetic Effects of Electric Current to understand the link between electricity and magnetism.

FAQs

Q1. What is NCERT Class 10 Science Chapter 11 about?
NCERT Class 10 Science Chapter 11 explains electric current, Ohm’s law, resistance, heating effect and electric power.

Q2. What is Ohm’s law in NCERT Class 10 Science Chapter 11?
Ohm’s law states that V = IR at constant temperature.

Q3. What is the unit of resistivity in NCERT Class 10 Science Chapter 11?
Ohm metre (Ω m).

Q4. What is the formula for electric power in NCERT Class 10 Science Chapter 11?
P = VI, P = I²R and P = V²/R.

Q5. Why is NCERT Class 10 Science Chapter 11 important for exams?
Because numerical problems from electricity are frequently asked in CBSE board exams.

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