Question

If a burning log is a black object with a surface area of 0.25 m2 and a temperature of 800 8c, how much power does it emit as thermal radiation?

Answer 1

The correct answer of this question: 18789.79 watt.

EXPLANATION:

As per the question, the surface area of the log is given as A = $0.25\ m^2$

The temperature of the of the surface of the log t = 800 $^0C$

We know that $t^0C\ =(273+t)\ K$

                      ⇒ 800 degree celsius= 800+273 K

                                                           = 1073 K.

Here, K stands for kelvin scale.

We are asked to calculate the thermal power radiation .

The power is defined as the amount of energy released per unit time.

Hence, power is calculated as-

                                Power P = $\sigma AT^4$

                                               = $5.67\times 10^{-8} \times 0.25\times (1073)^4\ watt$

                                               = 18789.79 watt.      [ans]

Here, $\sigma$ is the Stefan-Boltzmann constant and T is the absolute temperature of the log.