Question
A solid copper sphere (density ρ and specific heat capacity (c) of radius r at an initial temperature 200K is suspended inside a chamber whose walls are at almost 0K. The time required (in μ s) for the temperature of the sphere to drop to 100 K is
Answer: Option B
:
B
dTdt=σAmcJ(T4−T40) [In the given problem fall in temperature of body dT=(200-100)=100K , temp. of surrounding T0=0K, Initial temperature of body T=200k].
100dt=σ4πr243πr3ρcJ(2004−04)
⇒dt=rρcJ48σ×10−6s=rρcσ.4.248×10−6 [As J = 4.2]
780rρcσμs
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:
B
dTdt=σAmcJ(T4−T40) [In the given problem fall in temperature of body dT=(200-100)=100K , temp. of surrounding T0=0K, Initial temperature of body T=200k].
100dt=σ4πr243πr3ρcJ(2004−04)
⇒dt=rρcJ48σ×10−6s=rρcσ.4.248×10−6 [As J = 4.2]
780rρcσμs
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