Electricity – Class 10 Physics Chapter 11

Electricity

Electricity is the flow of electric charge (usually electrons) through a conductor. It is one of the most important forms of energy in modern life.

Electric Current

Electric current is the rate of flow of charge:

I = Q / t

Where: I = current (Ampere, A), Q = charge (Coulomb, C), t = time (seconds)

1 Ampere = 1 Coulomb of charge flowing per second.

Electric Potential and Potential Difference

The work done in moving a unit positive charge from one point to another is called potential difference:

V = W / Q

Unit: Volt (V). 1V = 1 Joule / 1 Coulomb.

Ohm's Law

At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends:

V = IR

Where R = resistance (in Ohms, Ω).

Factors Affecting Resistance

R = ρ × l / A

• ρ (rho): Resistivity of the material (Ω·m)
• l: Length of the conductor (R ∝ l)
• A: Cross-sectional area (R ∝ 1/A)

Metals have low resistivity (good conductors); rubber and glass have very high resistivity (insulators).

Resistors in Series

R_total = R₁ + R₂ + R₃ + ...

Current is the same through all resistors; voltage divides.

Resistors in Parallel

1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + ...

Voltage is the same across all resistors; current divides.

Electrical Energy and Power

P = V × I = I²R = V²/R

Energy = P × t

Unit of power: Watt (W). 1 kWh (kilowatt-hour) = 3.6 × 10⁶ Joules = 1 "unit" of electricity.

Heating Effect of Current

When current flows through a resistance, electrical energy is converted to heat:

H = I²Rt (Joule's Law of Heating)

Applications: electric heater, iron, fuse wire, electric bulb.

Reference: NCERT Science Textbook for Class 10 – Chapter 11; SL Arora Physics; Lakhmir Singh Physics.