Question

the emissive power of sphere of area 0.02 m^2 is 0.5kcal s^-1m-^2 .what is the amount of heat rsladiated by the spherical surface in 20 seconds​

Answer 1

Given that,

Emissive power $E= 0.5\ kcal/m^2s$

Area $A=0.02\ m^2$

Time = 20 sec

We need to calculate the amount of heat

Using formula of emissive power

$E=\dfrac{Q}{At}$

$Q=EAt$

Where, E = emissive power

A = area

t = time

Put the value into the formula

$Q=0.5\times10^3\times0.02\times20$

$Q=200\ cal$

$Q=200\times4.184\ J$

$Q= 836.8\ J$

Hence, The amount of heat is 836.8 J.