Generated by claude-sonnet-4-6 · 2026-06-15 06:45 · grounding rag
Model Answer
(i) Joule's Law of Heating:
The heat produced in a resistor is directly proportional to the square of the current (I²), the resistance (R), and the time (t) for which the current flows.
Mathematically:
$$H = I^2 R t$$
Since $I = V/R$, substituting:
$$H = \frac{V^2}{R} \cdot t \quad \text{or} \quad H = VIt$$
(ii) Given: R = 5 Ω, V = 6 V, t = 10 s
Current: $I = \dfrac{V}{R} = \dfrac{6}{5} = 1.2 \text{ A}$
Energy dissipated as heat:
$$H = I^2 R t = (1.2)^2 \times 5 \times 10 = 1.44 \times 50 = 72 \text{ J}$$
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Explanation
- For part (i), state the law in words first, then write H = I²Rt. Examiners also accept the alternate forms H = V²t/R or H = VIt since the question asks to express it for voltage V, current I, resistance R, and time t.
- For part (ii), find current using Ohm's law first, then apply H = I²Rt. You can also directly use H = V²t/R = (36×10)/5 = 72 J — either method gets full marks.
- Always include units (joules) in the final answer.