12
CBSE Marks
★★★★★
Difficulty
10
Topics
Very High
Board Weight
Topics Covered
10 key topics in this chapter
Electric Charge & Current
Potential Difference & EMF
Ohm's Law
Resistance & Resistivity
Factors Affecting Resistance
Resistors in Series
Resistors in Parallel
Heating Effect: Joule's Law
Electric Power
Domestic Electric Circuits
Study Resources
Key Formulas & Reactions
| Formula / Reaction / Rule | Expression |
|---|---|
| Ohm's Law | \(V = IR\) |
| Resistance | \(R = ρL/A\) |
| Series | \(R_eq = R₁ + R₂ + R₃\) |
| Parallel | \(1/R_eq = 1/R₁ + 1/R₂ + 1/R₃\) |
| Joule's Heating | \(H = I²Rt (joules)\) |
| Power | \(P = VI = I²R = V²/R (watts)\) |
| Electrical Energy | \(W = Pt (joules) | 1 kWh = 3.6 × 10⁶ J\) |
| Current | \(I = Q/t (amperes)\) |
Important Points to Remember
Ohm's Law: V = IR (at constant temperature). Resistance R = ρL/A where ρ = resistivity, L = length, A = cross-section area.
Series circuit: R_total = R₁ + R₂ + R₃. Current is same; voltage divides.
Parallel circuit: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃. Voltage is same; current divides.
Joule's Law of Heating: H = I²Rt. Electric power P = VI = I²R = V²/R. 1 kWh = 3.6 × 10⁶ J.