The heating effect of electric current is described by: MCQ with Answer and Explanation

The heating effect of electric current is described by:
A. Joule's law
B. Lenz's law
C. Faraday's law
D. Ohm's law
Answer: Option A
Solution (By JKExamLibrary)
Joule's law states that heat produced H = I²Rt, where I is current, R resistance, t time. This quantifies electrical energy converted to thermal energy in resistors. Ohm's law relates V, I, R; Faraday's and Lenz's laws concern electromagnetic induction. Memory aid: 'Joule heating ∝ I²R'. This definition-based question tests knowledge of fundamental laws in electricity, commonly examined in competitive exams. Applications include electric heaters, fuses, and incandescent bulbs. Always distinguish Joule's law (heating) from power formulas (P=VI=I²R=V²/R).

This question belongs to: Science Physics

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A wire of resistance 5 Ω is bent into a circle. The effective resistance between ends of a diameter is
A. 5 Ω
B. 1.25 Ω
C. 2.5 Ω
D. 10 Ω

Correct Answer: Option B


Explanation:
Circle total resistance 5 Ω. Across diameter, two halves in parallel, each half 2.5 Ω. Parallel: R = (2.5×2.5)/(2.5+2.5) = 6.25/5 = 1.25 Ω. Equal parallel resistors gives half of each.

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Water boils at a lower temperature at high altitudes because
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Correct Answer: Option A


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Resistance of wire: R = ρL/A. If length tripled and area doubled, new R is:
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Correct Answer: Option A


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This question belongs to: Science Physics