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

The heating effect of electric current is described by:
A. Faraday's law
B. Joule's law
C. Lenz's law
D. Ohm's law
Answer: Option B
Solution (By JKSSB Mock Tests)
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).

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Practice More Physics Questions

Question #1
Laws of reflection state that:
A. Light bends towards normal
B. Incident ray, reflected ray, and normal lie in same plane
C. Angle of incidence equals angle of reflection
D. Both (a) and (b)

Correct Answer: Option D


Explanation:
Laws of reflection: (1) Angle of incidence (i) equals angle of reflection (r); (2) Incident ray, reflected ray, and normal at point of incidence all lie in the same plane. Option D describes refraction, not reflection. These laws hold for all reflecting surfaces (plane, curved). Memory tip: 'i = r and coplanar rays'. This definition-based question tests precise recall of fundamental optics laws, frequently examined in competitive exams. Always distinguish reflection laws (i=r) from refraction laws (Snell's law: n₁sin i = n₂sin r).

This question belongs to: Science Physics
Question #2
An object is placed between pole and focus of a concave mirror. The image is
A. Real, erect, enlarged
B. Real, inverted, enlarged
C. Virtual, inverted, diminished
D. Virtual, erect, enlarged

Correct Answer: Option D


Explanation:
Object between P and F of concave mirror gives virtual, erect, magnified image behind mirror. Used in shaving mirror, dentist mirror. Ray diagram shows diverging rays appearing to come from behind.

This question belongs to: Science Physics
Question #3
The weight of a body is zero when it is
A. At poles
B. At centre of Earth
C. On moon
D. In orbit

Correct Answer: Option B


Explanation:
g=0 at centre, so weight zero.

This question belongs to: Science Physics