Two copper spheres of radii 6 cm and 12 cm respectively are suspended in an evacuated. Each of them is at a temperature `15^(@)C` above the surroundings. The ratio of their of loss of heat is

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

Two spheres of same material and radius r and 2r are heated to same temperature and are kept in identical surroundings, ratio of their rate of loss of heat is

Two spheres of same material and radius r and 2r are heated to same temperature and are kept in identical surroundings, ratio of their rate of loss of heat is

A sphere and a cube both made of copper have equal volumes and are blackened. These are heated to same temperature and are allowed to cool under same surroundings. The ratio of their rates of loss of heat is

Two solid copper spheres of radii r_1=15cm and r_2=20cm are both at a temperature of 60^@ C. If the temperature of surrounding is 50^@C , then find a. The ratio of the heat loss per second from their surfaces initially. b. the ratio of rates of cooling initially.

Two solid copper spheres of radii r_1=15cm and r_2=20cm are both at a temperature of 60^@ C. If the temperature of surrounding is 50^@C , then find a. The ratio of the heat loss per second from their surfaces initially. b. the ratio of rates of cooling initially.