According to Joule's law of heating, the rate of heat produced in a resistor is
(A) directly proportional to the current for the given resistance
(B) directly proportional to the square of the current for the given resistance
(C) directly proportional to the resistance for a given value of current
(D) inversely proportional to the resistance for a given voltage
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B), (C) and (D) only
By Joule's law the rate of heat production in a resistor is the power dissipated, \( P = I^{2}R = V^{2}/R \).
(A) directly proportional to the current for the given resistance — Incorrect. For a given \( R \), \( P = I^{2}R \) varies as the square of the current, not as the current.
(B) directly proportional to the square of the current for the given resistance — Correct. \( P = I^{2}R \propto I^{2} \) when \( R \) is fixed.
(C) directly proportional to the resistance for a given value of current — Correct. \( P = I^{2}R \propto R \) when \( I \) is fixed.
(D) inversely proportional to the resistance for a given voltage — Correct. \( P = V^{2}/R \propto 1/R \) when \( V \) is fixed.
Statements (B), (C) and (D) are correct, which is Option (4).
NCERT (2026-27):
Electrical Energy, Power – “… The energy dissipated per unit time is the power dissipated P = ΔW/Δt and we have,
\( \displaystyle P = IV \qquad (3.32) \)
Using Ohm’s law V = IR, we get
\( \displaystyle P = I^2 R = V^2/R \qquad (3.33) \)
as the power loss (“ohmic loss”) in a conductor of resistance R carrying a current I. It is this power which heats up, for example, the coil of an electric bulb to incandescence, radiating out heat and light.”