2007 AIPMT-PRE Thermal Properties of MatterStefan–Boltzmann law Easy Question 2 of 5 in Stefan–Boltzmann law

A black body is at $727^\circ C$. It emits energy at a rate which is proportional to

A $(1000)^4$
B $(1000)^2$
C $(727)^4$
D $(727)^2$

The answer is A.

Solution

According to Stefan's law, the energy emitted per second by a black body is proportional to the fourth power of its absolute temperature: $E \propto T^4$
The temperature must be in kelvin: $T = (t + 273)$ K
$727^\circ C = (727 + 273)$ K $= 1000$ K
$E \propto (727 + 273)^4$
$E \propto (1000)^4$

Concept Stefan's law uses absolute temperature

Stefan–Boltzmann law in past papers

5 questions from this chapter have appeared across 3 exam years.