Read the following statements :
A. When small temperature difference between a liquid and its surrounding is doubled the rate of loss of heat of the liquid becomes twice.
B. Two bodies $P$ and $Q$ having equal surface areas are maintained at temperature $10^\circ$C and $20^\circ$C. The thermal radiation emitted in a given time by $P$ and $Q$ are in the ratio $1 : 1.15$
C. A carnot Engine working between $100$ K and $400$ K has an efficiency of $75\%$
D. When small temperature difference between a liquid and its surrounding is quadrupled, the rate of loss of heat of the liquid becomes twice.
Choose the correct answer from the options given below :
Answer: (A) A, B, C only
A: True. By Newton's law of cooling the rate of loss of heat is proportional to a small temperature difference.
B: True. $\dfrac{E_Q}{E_P} = \left(\dfrac{293}{283}\right)^4 \approx 1.15$.
C: True. $\eta = 1 - \dfrac{100}{400} = 75\%$.
D: False. Quadrupling the difference makes the rate four times, not twice.
A, B, C only.
Solution by Sreeraj P, M.Sc Physics