Chapter 11: Electricity
Simple, exam-focused CBSE Class 10 Science notes — star topics, concepts, common mistakes, and previous year question patterns, all on one page.
Chapter 11: Electricity
⭐ Star Topics / Most Important
- Ohm's Law and numerical problems
- Resistance in series and parallel
- Heating effect of electric current (Joule's law)
- Electric power and household circuits
Detailed Chapter Notes
Electric current I = Q/t (amperes). Potential difference V = W/Q (volts).
Ohm's Law: V = IR. Resistance R = ρL/A — depends on material, length (direct), and area (inverse). Resistivity is an intrinsic material property, not dependent on shape/size.
Series: current same, voltage divides; Rtotal = R1+R2+R3 (always more than the largest). Parallel: voltage same, current divides; 1/Rtotal = 1/R1+1/R2+1/R3 (always less than the smallest) — this is why household wiring uses parallel connections.
Joule's heating: H = I²Rt — working principle of heaters, geysers, and fuses (low melting point, high resistance, melts to break the circuit when current exceeds safe limits).
Electric power: P = VI = I²R = V²/R (watts). Commercial unit: kilowatt-hour (kWh) — 1 kWh = 3.6 × 10^6 joules.
The most common numerical error is mixing up series and parallel formulas under exam pressure — series ADDS resistances, parallel adds RECIPROCALS. Also, resistivity depends only on material and temperature, never on length or area — it's resistance that depends on dimensions.
Search on YouTube: Electricity Class 10 numericals Ohm's law tricks for a visual walkthrough of this chapter.
- State Ohm's Law. Draw the circuit diagram to verify it experimentally (3 marks)
- Two resistors of 4Ω and 6Ω are connected in parallel. Find the equivalent resistance (numerical, 2 marks)
- Why is resistance independent of resistivity but dependent on length and area? Explain the difference (2 marks, HOTS)
- Why are household circuits connected in parallel rather than series? (3 marks)
- Calculate the heat produced in 10 seconds by a current of 2A through a 5Ω resistor (numerical, 2 marks)