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Barış Köse 2

Barış K.

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To heat 1 cup of water (250 cm$^3$) to make coffee, you place an electric heating element in the cup. As the water temperature increases from 20$^\circ$C to 78$^\circ$C, the temperature of the heating element remains at a constant 120$^\circ$C. Calculate the change in entropy of (a) the water; (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section 20.7, and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.

To heat 1 cup of water (250 cm$^3$) to make coffee, you place an electric heating element in the cup. As the water temperature increases from 20$^\circ$C to 78$^\circ$C, the temperature of the heating element remains at a constant 120$^\circ$C. Calculate the change in entropy of (a) the water; (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section 20.7, and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.

University Physics with Modern Physics

To heat 1 cup of water $\left(250 \mathrm{~cm}^{3}\right)$ to make coffee, you place an electric heating element in the cup. As the water lemperature increases from $20^{\circ} \mathrm{C}$ to $78^{\circ} \mathrm{C}$, the temperature of the heating element remains at a constant $120^{\circ} \mathrm{C}$. Calculate the change in entropy of (a) the water, (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section $20.7,$ and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.

To heat 1 cup of water $\left(250 \mathrm{~cm}^{3}\right)$ to make coffee, you place an electric heating element in the cup. As the water lemperature increases from $20^{\circ} \mathrm{C}$ to $78^{\circ} \mathrm{C}$, the temperature of the heating element remains at a constant $120^{\circ} \mathrm{C}$. Calculate the change in entropy of (a) the water, (b) the heating element; (c) the system of water and heating element. (Make the same assumption about the specific heat of water as in Example 20.10 in Section $20.7,$ and ignore the heat that flows into the ceramic coffee cup itself.) (d) Is this process reversible or irreversible? Explain.

University Physics with Modern Physics

A heat engine uses a large insulated tank of ice water as its cold reservoir. In 100 cycles the engine takes in $8000 \mathrm{~J}$ of heat energy from the hot reservoir and the rejected heat melts $0.0180 \mathrm{~kg}$ of ice in the tank. During these 100 cycles, how much work is performed by the engine?

A heat engine uses a large insulated tank of ice water as its cold reservoir. In 100 cycles the engine takes in $8000 \mathrm{~J}$ of heat energy from the hot reservoir and the rejected heat melts $0.0180 \mathrm{~kg}$ of ice in the tank. During these 100 cycles, how much work is performed by the engine?

University Physics with Modern Physics

Find an arc length parametrization of the curve parametrized by $\mathbf{r}(t)=\left\langle t^{2}, t^{3}\right\rangle$.

Find an arc length parametrization of the curve parametrized by $\mathbf{r}(t)=\left\langle t^{2}, t^{3}\right\rangle$.

Calculus: Early Transcendentals

Calculus of Vector Valued Functions

Arc Length and Speed

Questions asked

INSTANT ANSWER

Learning Goal: To understand that a heat engine run backward is a heat pump that can be used as a refrigerator. By now you should be familiar with heat engines--devices, theoretical or actual, designed to convert heat into work. You should understand the following: Heat engines must be cyclical; that is, they must return to their original state some time after having absorbed some heat and done some work). Heat engines cannot convert heat into work without generating some waste heat in the process. The second characteristic is a rigorous result even for a perfect engine and follows from thermodynamics. A perfect heat engine is reversible, another result of the laws of thermodynamics. If a heat engine is run backward (i.e., with every input and output reversed), it becomes a heat pump (as pictured schematically (Figure 1)). Work Win must be put into a heat pump, and it then pumps heat from a colder temperature Tc to a hotter temperature Th, that is, against the usual direction of heat flow (which explains why it is called a "heat pump"). The heat coming out the hot side Qh of a heat pump or the heat going in to the cold side Qc of a refrigerator is more than the work put in; in fact it can be many times larger. For this reason, the ratio of the heat to the work in heat pumps and refrigerators is called the coefficient of performance, K. In a refrigerator, this is the ratio of heat removed from the cold side Qc to work put in: Kfrig=QcWin. In a heat pump the coefficient of performance is the ratio of heat exiting the hot side Qh to the work put in: Kpump=QhWin. Take Qh, and Qc to be the magnitudes of the heat emitted and absorbed respectively. What is the relationship of Win to the work W done by the system? Express Win in terms of W and other quantities given in the introduction.

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ANSWERED

Prabhu Ramji verified

Numerade educator

A heat engine uses a large insulated tank of ice water as its cold reservoir. In 100 cycles the engine takes in 8000 J of heat energy from the hot reservoir and the rejected heat melts 0.0180 kg of ice in the tank. During these 100 cycles, how much work is performed by the engine?

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INSTANT ANSWER

The inside of an ideal refrigerator is at a temperature Tc, while the heating coils on the back of the refrigerator are at a temperature Th. Owing to a malfunctioning switch, the light bulb within the refrigerator remains on when the the door is closed. The power of the light bulb is P; assume that all of the energy generated by the light bulb goes into heating the inside of the refrigerator. For all parts of this problem, you must assume that the refrigerator operates as an ideal Carnot engine in reverse between the respective temperatures. Suppose the refrigerator has a 25-W light bulb, the temperature inside the refrigerator is 0∘C, and the temperature of the heat dissipation coils on the back of the refrigerator is 35∘C. Find the extra power Pextra consumed by the refrigerator. Keep in mind that you will need to use absolute units of temperature (i.e., kelvins). Express your answer numerically in watts to three significant figures.

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INSTANT ANSWER

The inside of an ideal refrigerator is at a temperature Tc, while the heating coils on the back of the refrigerator are at a temperature Th. Owing to a malfunctioning switch, the light bulb within the refrigerator remains on when the the door is closed. The power of the light bulb is P; assume that all of the energy generated by the light bulb goes into heating the inside of the refrigerator. For all parts of this problem, you must assume that the refrigerator operates as an ideal Carnot engine in reverse between the respective temperatures. If the temperatures inside and outside of the refrigerator do not change, how much extra power Pextra does the refrigerator consume as a result of the malfunction of the switch? Express the extra power in terms of P, Th, and Tc.

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INSTANT ANSWER

Steam at a temperature TH = 260 ∘C and p = 1.00 atm enters a heat engine at an unknown flow rate. After passing through the heat engine, it is released at a temperature TC = 100 ∘C and p = 1.00 atm. The measured power output P of the engine is 160 J/s, and the exiting steam has a heat transfer rate of HC = 4000 J/s. Find the efficiency e of the engine and the molar flow rate n/t of steam through the engine. The constant pressure molar heat capacity Cp for steam is 37.47 J/(mol⋅K). Which of the following quantities are known? The molar flow rate of steam, n/t The temperature of the steam as it enters the engine, TH The heat transfer rate for steam entering the engine, HH The constant pressure molar heat capacity of steam, Cp The power output of the engine, P The efficiency of the engine, e The temperature of steam as it leaves the engine, TC The heat transfer rate for steam leaving the engine, HC

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