Electricity (Chapter 11) brings at least one numerical and one circuit question every year in CBSE Class 10. These notes cover every formula with a worked example.
Basic quantities
| Quantity | Formula | Unit |
|---|---|---|
| Current | I = Q/t | Ampere (A) |
| Potential difference | V = W/Q | Volt (V) |
| Resistance | R = V/I (Ohm’s law) | Ohm (Ω) |
| Resistance of a wire | R = ρl/A | ρ in Ω m |
Series vs parallel
| Series | Parallel | |
|---|---|---|
| Total resistance | R = R₁ + R₂ + R₃ | 1/R = 1/R₁ + 1/R₂ + 1/R₃ |
| Current | Same through each | Divides |
| Voltage | Divides | Same across each |
| Used in | Decorative lights | Home wiring |
Heating effect and power
- Heat H = I²Rt (Joule’s law)
- Power P = VI = I²R = V²/R
- Energy = P × t; 1 kWh (1 unit) = 3.6 × 10⁶ J
Solved numericals
1. A 100 W bulb runs on 220 V. Current = 100/220 = 0.45 A; resistance = 220²/100 = 484 Ω.
2. Three resistors 2 Ω, 3 Ω, 6 Ω in parallel: 1/R = 1/2 + 1/3 + 1/6 = 1 → R = 1 Ω.
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3. A heater of 1 kW used 2 h daily for 30 days: energy = 1 × 2 × 30 = 60 kWh → at ₹6/unit, bill = ₹360.
4. A wire of resistance R is stretched to double its length: A halves, l doubles → R becomes 4R.
Common mistakes
- Adding resistances directly in parallel
- Using V²/R when the voltage across that resistor is not V
- Forgetting to convert hours to seconds in H = I²Rt
Related: Light Class 10 notes.
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Frequently asked questions
Are these Electricity Class 10 Notes notes enough for the exam?
They cover every formula, definition and question type that appears in school and board papers for this chapter. Use them with the NCERT examples, exercise questions and the last five years' papers to be fully prepared.
How should I revise Electricity Class 10 Notes?
Revise the notes after 1 day, 7 days and 30 days. Solve five questions each time instead of only reading, and keep an error list of the steps you get wrong.
What if I get stuck on a electricity class 10 question?
Type or photograph the exact question on DoubtPay AI, choose your class and language, and get a step-by-step answer with a diagram. You can also ask for a hint or have your own attempt checked. Packs start at ₹9 for 15 answers.
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