Example 1 · level 1
A current of 2 A flows through a 5 Ω heater coil for 30 s. Find the heat produced (in J).
Show solution
- H = 2² × 5 × 30 = 600 J.
Answer: 600 J
CLASS 10 SCIENCE · ELECTRICITY
Heating effect of current (Joule’s law)
Heat produced H = I²Rt (joule). Doubling the current makes the heat four times.
Loading practice…
Worked examples
Example 2 · level 2
A 50 Ω resistor is connected across 50 V for 30 s. Find the heat produced (in J).
Show solution
- I = 50 ÷ 50 = 1 A.
- H = 1 × 50 × 30 = 1,500 J.
Answer: 1,500 J
Example 3 · level 3
A coil produces 19,200 J of heat in 120 s when a current of 2 A passes through it. Find its resistance (in ohm).
Show solution
- R = 19,200 ÷ 480 = 40 Ω.
Answer: 40 ohm