Question

Two copperr spheres of radii 6 cm and 12 cm respectively are suspended in an evacuated enclosure. Each of them are at a temperature `15^(@)C` above the surroundings. The ratio of their rate of loss of heat is
A. `2:1`
B. `1:4`
C. `1:8`
D. `8:1`

Answer 1

Correct Answer - B
`((dQ)/(dt))_(1)//((dQ)/(dt))_(2)=(A_(1))/(A_(2))=(4pir_(1)^(2))/(4pir_(2)^(2))=((r_(1))/(r_(2)))^(2)`
`=((6)/(12))^(2)=((1)/(2))^(2)=(1)/(4)`