Question

A 30 Ohm resistor carrying a constant current of 1A is kept at constant temperature of ${27}^{o}C$ by a stream of a cooling water. In a time interval of 1 sec, what is change in entropy of universe ?

• A. 0.1 J/K
• B. 0.1 kJ/K
• C. 10 J/K
• D. 10 kJ/K

Answer 1

The correct option is A 0.1 J/K

$T=C;T_2=T_1$

$(dS{)}_R=mcln\left(\frac{T_2}{T_1}\right)$

$(dS{)}_R=0$

$(dS{)}_{surr}=\frac{dQ}{T}$

$=\frac{I^{2}R\times time}{(273+27)}$

$=\frac{(I{)}^2\times 50\times 1}{\left(300\right)}=0.1J/K$