Q1. [1] § 11.7 HEATING EFFECT OF ELECTRIC CURRENT § 11.7.1 Practical Applications of Heating Effect of Electric Current § 11.8 ELECTRIC POWER
An electric iron of resistance 20 Ω draws a current of 5 A. The heat developed in the iron in 30 seconds is :
- A 15000 J
- B 6000 J
- C 1500 J
- D 3000 J
Previously asked in CBSE board exam
2024 31/4/1 Q14
Generated by claude-sonnet-4-6 · 2026-06-15 06:43 · grounding rag
Model Answer
Option A: 15000 J
Using Joule's law of heating: $H = I^2Rt = (5)^2 \times 20 \times 30 = 25 \times 20 \times 30 = \mathbf{15000 \text{ J}}$
Source: Chapter 11, Section 11.7 (Heating Effect of Electric Current)
Explanation
Apply the formula $H = I^2Rt$ directly. Students must remember to square the current first — a common error is writing $I \times R \times t$ instead of $I^2 \times R \times t$. This question is a direct application of Joule's law.
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