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 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

A body is heated to a temperature of 75^(@)C and is allowed to cool. If the temperature of the surrounding is 35^(@)C , then the temperature at which the rate of cooling will be exactly half of that initially will be

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 uniform solid spheres made of copper have radii 15 cm and 20 cm respectively. Both of them are heated to a temperature of 70^(@)C and then placed in a region of ambient temperature equal to 45^(@)C . What will be the ratio of the initial rates of cooling of both the spheres?

Two uniform solid spheres made of copper have radii 15 cm and 20 cm respectively. Both of them are heated to a temperature of 70^(@)C and then placed in a region of ambient temperature equal to 45^(@)C . What will be the ratio of the initial rates of cooling of both the spheres?

Two identical spheres A and B are suspended in an air chamber which is maintained at a temperature of 50^@C . Find the ratio of the heat lost per second from the surface of the spheres if a. A and B are at temperatures 60^@C and 55^@C , respectively. b. A and B are at temperatures 250^@C and 200^@C , respectively.

Two identical spheres A and B are suspended in an air chamber which is maintained at a temperature of 50^@C . Find the ratio of the heat lost per second from the surface of the spheres if a. A and B are at temperatures 60^@C and 55^@C , respectively. b. A and B are at temperatures 250^@C and 200^@C , respectively.

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