Read the following statements:A. When the sma | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(A) $A.$ According to Newton's law of cooling,the rate of loss of heat $\frac{dQ}{dt} \propto \Delta T$. If $\Delta T$ is doubled,the rate of loss of

Vedclass · Accepted Answer

$A, B, C$ only

Vedclass · Answer

(A) $A.$ According to Newton's law of cooling,the rate of loss of heat $\frac{dQ}{dt} \propto \Delta T$. If $\Delta T$ is doubled,the rate of loss of heat becomes twice. Thus,$A$ is correct.$B.$ The power radiated by a body is $P = \sigma e A T^4$. The ratio of radiation emitted is $\frac{H_P}{H_Q} = \left(\frac{T_P}{T_Q}\right)^4$. Converting temperatures to Kelvin: $T_P = 10 + 273 = 283 K$ and $T_Q = 20 + 273 = 293 K$. Thus,$\frac{H_P}{H_Q} = \left(\frac{283}{293}\right)^4 \approx (0.9658)^4 \approx 0.87$. However,using the approximation $\frac{293}{283} \approx 1.035$,then $(1.035)^4 \approx 1.15$. Thus,$1:1.15$ is correct. $B$ is correct.$C.$ Efficiency $\eta = 1 - \frac{T_L}{T_H} = 1 - \frac{100}{400} = 1 - 0.25 = 0.75$ or $75\%$. Thus,$C$ is correct.$D.$ Since $\frac{dQ}{dt} \propto \Delta T$,if $\Delta T$ is quadrupled,the rate of loss of heat becomes four times,not twice. Thus,$D$ is incorrect.Therefore,statements $A, B,$ and $C$ are correct.

Similar Questions

The $P-V$ diagram of a certain process (Carnot cycle) is as shown. The process is also represented as:

When $100 \ J$ of heat is supplied to a gas,the increase in the internal energy of the gas is $60 \ J$. Then the gas is/can

An engineer claims to have made an engine delivering $10 \, kW$ power with fuel consumption of $1 \, g \, s^{-1}$. The calorific value of the fuel is $2 \, kcal \, g^{-1}$. His claim:

Vedclass Test Series

Exam Paper Generator

Online Exam Module