Please solve the problem(and list the necessary steps so that I can understand).
ID: 1999074 • Letter: P
Question
Please solve the problem(and list the necessary steps so that I can understand). And I already looked at the scribd solution manual. So, please help me understand how to solve this problem. Thank you.
6-5 A thermally insulated resistor of 20 ohms has a current of 2A passed through it for 1 second. It is initially at 20°C. The mass of the resistor is 5 g cP for the resis- tor is 850 J kg K (a) What is the temperature rise? (b) What is the entropy change of the resistor and the universe? (Hint: In the actual process, dissipative work is done on the resistor. Imagine a reversible process taking it between the same equilibrium states.)Explanation / Answer
current I = 2 A
resistance R = 20 ohm
power = I2R
time = 1s
Energy disssipated in the resistor = 22*20*1 = 80 J
Cp = 850J/kg/K
mass m = 5g = 5e-3 kg
temperature raised = (80/850)*(1/5e-3)
= 18.82 0C
b)
entropy change of the resistor = 80/18.2 = 4.25 J/K
The resistor is thermally insulated and no heat is passed on to the surroundigs.
Change in entropy of the Universe is 0.