Electricity Class 10 – Ohm's Law, Resistors & Joule's Heating NCERT Solutions
Master Class 10 Physics Electricity: Ohm's law, series and parallel circuits, resistivity, electrical power, Joule's law of heating, and solved numericals.
Electricity – Complete Chapter Revision & Solutions
Electricity is a controllable and convenient form of energy. Electric current (I) is defined as the rate of flow of electric charges across any cross-section of a conductor.
Ohm's Law & Resistance
V = I × R (where R is the electrical resistance, in Ohms, Ω)
Factors Affecting Resistance & Resistivity
R = ρ × (l / A)Where: l = length of conductor (m), A = cross-sectional area (m²), ρ = specific electrical resistivity of material (Ω·m).
Combination of Resistors
| Feature | Series Combination | Parallel Combination |
|---|---|---|
| Equivalent Formula | R_eq = R₁ + R₂ + R₃ | 1/R_eq = 1/R₁ + 1/R₂ + 1/R₃ |
| Current (I) | Same through every resistor | Divides among branches: I = I₁ + I₂ + I₃ |
| Voltage (V) | Divides across resistors: V = V₁ + V₂ + V₃ | Same voltage across all parallel branches |
| Overall Resistance | Greater than the largest resistor | Smaller than the smallest individual resistor |
Joule's Law of Heating & Electric Power
H = I²Rt = VIt = (V² / R) × t (Joules)Electric Power:
P = V × I = I²R = V² / R (Watts)Commercial Unit: 1 kilowatt-hour (1 kWh) = 3.6 × 10⁶ Joules = 1 Unit of electricity.
An electric lamp of resistance 20 Ω and a conductor of 4 Ω resistance are connected in series to a 6 V battery. Calculate:
(a) The total resistance of the circuit,
(b) The current flowing through the circuit,
(c) The potential difference across the lamp and the conductor.
(a) Total Resistance in Series:
R_total = R_lamp + R_conductor = 20 Ω + 4 Ω = 24 Ω
(b) Current in Circuit (Ohm's Law):
I = V / R_total = 6 V / 24 Ω = 0.25 A
(c) Potential Difference Across Each:
• Across Lamp: V₁ = I × R_lamp = 0.25 A × 20 Ω = 5.0 V
• Across Conductor: V₂ = I × R_conductor = 0.25 A × 4 Ω = 1.0 V
Check: V₁ + V₂ = 5.0 V + 1.0 V = 6.0 V (Matches battery voltage!)
Indexed Topics & Examination Keywords
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