(a) Suppose a 500 resistor is immersed in an oil bath. The oil bath is kept at a constant temperature of 25°C and constant pressure of 1 atm. An experiment is performed, where a current of 75mA is made to flow in the resistor for 30s. Find the entropy change of the resistor and of the oil bath. [Hint: assume that at the beginning and end of the experiment, the temperature of the resistor is equal to that of the oil bath. The heat per unit time produced by an electrical component with resistance R, while current I is flowing through it, is Q/At = I? R] (b) Now suppose that instead of the resistor being placed in an oil bath, the resistor is thermally insulated (you enclose it in an adiabatic wrapping). The resistor has a mass of 4g and the material from which it is made has a specific heat at constant pressure of 750 J/kg/K. The other parameters for the experiment are the same as in part (a). What is the change in entropy of the resistor, assuming its volume change is negligible during the experiment? (c) The experimenter in Part (a) has extra supplies of oil sitting in the lab. Suppose there are two rigid containers of oil, which are in thermal contact with each other but completely isolated from the environment. Suppose the entropy of the oil in a container is given by the experimentally-determined approximation: S = a V(n v U) where a is an experimentally-determined constant for the oil. The second container has twice as many moles of oil (n), and three times the internal energy (U), as the first container. Find the (approximate) ratio of the volumes of the systems.
(a) Suppose a 500 resistor is immersed in an oil bath. The oil bath is kept at a constant temperature of 25°C and constant pressure of 1 atm. An experiment is performed, where a current of 75mA is made to flow in the resistor for 30s. Find the entropy change of the resistor and of the oil bath. [Hint: assume that at the beginning and end of the experiment, the temperature of the resistor is equal to that of the oil bath. The heat per unit time produced by an electrical component with resistance R, while current I is flowing through it, is Q/At = I? R] (b) Now suppose that instead of the resistor being placed in an oil bath, the resistor is thermally insulated (you enclose it in an adiabatic wrapping). The resistor has a mass of 4g and the material from which it is made has a specific heat at constant pressure of 750 J/kg/K. The other parameters for the experiment are the same as in part (a). What is the change in entropy of the resistor, assuming its volume change is negligible during the experiment? (c) The experimenter in Part (a) has extra supplies of oil sitting in the lab. Suppose there are two rigid containers of oil, which are in thermal contact with each other but completely isolated from the environment. Suppose the entropy of the oil in a container is given by the experimentally-determined approximation: S = a V(n v U) where a is an experimentally-determined constant for the oil. The second container has twice as many moles of oil (n), and three times the internal energy (U), as the first container. Find the (approximate) ratio of the volumes of the systems.
Chapter4: The Second Law Of Thermodynamics
Section: Chapter Questions
Problem 31P: If a refrigerator discards 80 J of heat per cycle and its coefficient of performance is 6.0, what...
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![(a) Suppose a 500 resistor is immersed in an oil bath. The oil bath is kept at a constant temperature of
25°C and constant pressure of 1 atm. An experiment is performed, where a current of 75mA is made to
flow in the resistor for 30s. Find the entropy change of the resistor and of the oil bath.
[Hint: assume that at the beginning and end of the experiment, the temperature of the resistor is equal
to that of the oil bath. The heat per unit time produced by an electrical component with resistance R,
while current I is flowing through it, is Q/At = I ² R]
(b) Now suppose that instead of the resistor being placed in an oil bath, the resistor is thermally
insulated (you enclose it in an adiabatic wrapping). The resistor has a mass of 4g and the material from
which it is made has a specific heat at constant pressure of 750 J/kg/K. The other parameters for the
experiment are the same as in part (a). What is the change in entropy of the resistor, assuming its
volume change is negligible during the experiment?
(c) The experimenter in Part (a) has extra supplies of oil sitting in the lab. Suppose there are two rigid
containers of oil, which are in thermal contact with each other but completely isolated from the
environment. Suppose the entropy of the oil in a container is given by the experimentally-determined
approximation:
S = a V(n v U)
where a is an experimentally-determined constant for the oil. The second container has twice as many
moles of oil (n), and three times the internal energy (U), as the first container. Find the (approximate)
ratio of the volumes of the systems.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc0a416aa-90b7-478f-8c7c-e07ad14a269e%2Fa9809496-cc21-410c-a56a-349b8db91bc8%2Fh012jt_processed.jpeg&w=3840&q=75)
Transcribed Image Text:(a) Suppose a 500 resistor is immersed in an oil bath. The oil bath is kept at a constant temperature of
25°C and constant pressure of 1 atm. An experiment is performed, where a current of 75mA is made to
flow in the resistor for 30s. Find the entropy change of the resistor and of the oil bath.
[Hint: assume that at the beginning and end of the experiment, the temperature of the resistor is equal
to that of the oil bath. The heat per unit time produced by an electrical component with resistance R,
while current I is flowing through it, is Q/At = I ² R]
(b) Now suppose that instead of the resistor being placed in an oil bath, the resistor is thermally
insulated (you enclose it in an adiabatic wrapping). The resistor has a mass of 4g and the material from
which it is made has a specific heat at constant pressure of 750 J/kg/K. The other parameters for the
experiment are the same as in part (a). What is the change in entropy of the resistor, assuming its
volume change is negligible during the experiment?
(c) The experimenter in Part (a) has extra supplies of oil sitting in the lab. Suppose there are two rigid
containers of oil, which are in thermal contact with each other but completely isolated from the
environment. Suppose the entropy of the oil in a container is given by the experimentally-determined
approximation:
S = a V(n v U)
where a is an experimentally-determined constant for the oil. The second container has twice as many
moles of oil (n), and three times the internal energy (U), as the first container. Find the (approximate)
ratio of the volumes of the systems.
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