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# Two Copper 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 - Physics

#### Question

Two copper 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.................

1. 2:1
2. 1:4
3. 1:8
4. 8:1

#### Solution

(b) 1:4

r1 = 6 cm
r2 = 12 cm
T1 = T2 = 15°C
Ratio of loss of heat is

R_1/R_2=A_1/A_2xxT_1^4/T_2^4

R_1/R_2=(4pir_1^2)/(4pir_2^2)=6^2/12^2=1/4

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