Electricity Class 10 Notes
Ohm's law, resistors in series/parallel, heating effect, and electric power.
Electricity — Detailed Notes
Electricity is an important chapter in Science (Class 10) and is frequently tested in both conceptual and application-based questions. Students should first understand the core definition, then connect the topic with real-life observations and exam patterns.
Electricity involves the flow of electric charge (current) through conductors, governed by Ohm's law, and described by circuits with resistance, voltage, and power relationships. In school and entrance exams, questions usually check your conceptual clarity, step-wise logic, and ability to avoid common mistakes.
To prepare effectively, break Electricity into smaller sub-parts: definition, laws/rules, examples, formulas, and revision questions. After theory, solve short questions, then move to mixed-level numericals or application prompts.
A smart revision strategy is to maintain a one-page summary for Electricity. Include important terms, two solved examples, and last-minute checkpoints before exams.
Key Exam Points
- Electric current I = Q/t (A); potential difference V = W/Q (V); Ohm's law: V = IR.
- Resistance R = ρL/A; ρ is resistivity (material property), L = length, A = cross-section area.
- Series: R_total = R₁+R₂+...; same current, voltage divides. Parallel: 1/R_total = 1/R₁+1/R₂+...; same voltage, current divides.
- Power P = VI = I²R = V²/R (Watts); Electrical energy E = Pt (joules or kWh).
- 1 unit (kWh) = 1000W × 3600s = 3.6×10⁶ J; cost of electricity in ₹ based on units consumed.
- Heating effect (Joule's law): H = I²Rt; used in electric heaters, irons, incandescent bulbs, fuses.
Important Formula / Rule
V = IR | P = VI = I²R = V²/R | R_series = R₁+R₂ | 1/R_parallel = 1/R₁+1/R₂
What You Will Learn in Electricity
Electricity involves the flow of electric charge (current) through conductors, governed by Ohm's law, and described by circuits with resistance, voltage, and power relationships.
- Electric current I = Q/t (A); potential difference V = W/Q (V); Ohm's law: V = IR.
- Resistance R = ρL/A; ρ is resistivity (material property), L = length, A = cross-section area.
- Series: R_total = R₁+R₂+...; same current, voltage divides. Parallel: 1/R_total = 1/R₁+1/R₂+...; same voltage, current divides.
- Power P = VI = I²R = V²/R (Watts); Electrical energy E = Pt (joules or kWh).
- 1 unit (kWh) = 1000W × 3600s = 3.6×10⁶ J; cost of electricity in ₹ based on units consumed.
- Heating effect (Joule's law): H = I²Rt; used in electric heaters, irons, incandescent bulbs, fuses.
Key Formulas
V = IRP = VI = I²R = V²/RR_series = R₁+R₂1/R_parallel = 1/R₁+1/R₂
Example
A 100W bulb at 220V draws I=P/V=100/220≈0.45 A and has R=V²/P=484 Ω.
Solved Numerical Example
A wire 2m long, cross-section 0.5mm², resistivity 1.6×10⁻⁶ Ω·m. Find resistance. R = ρL/A = (1.6×10⁻⁶ × 2)/(0.5×10⁻⁶) = 3.2×10⁻⁶/5×10⁻⁷ = 6.4 Ω.
Expected Exam Questions — Electricity
Q1.Three resistors 2Ω, 3Ω, 6Ω are connected in parallel. Find equivalent resistance.
Q2.An electric iron rated 1000W, 220V is used for 2 hours daily for 30 days. Find units consumed and cost at ₹6/unit.
Q3.Why are household appliances connected in parallel?
🔘 MCQ Practice — Electricity
MCQ 1.If a wire's length is doubled and diameter is halved, its resistance becomes:
✓ Correct Answer: 8R
Download Electricity PDF Notes
Get the complete Electricity notes as a PDF — free for enrolled students, or browse our public study materials library.