When there is temperature difference between two systems, there will be a transfer of thermal energy from the system of high temperature to the system of low temperature by one or more of * .three distance processes

When there is temperature difference between two systems, there will be a transfer of thermal energy from the system of high temperature to the system of low temperature by one or more of * .three distance processes

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter21: Heat And The First Law Of Thermodynamics

Section: Chapter Questions

Problem 4PQ

See similar textbooks

Similar questions

One method of converting heat transfer to doing work is for heat transfer into a gas to take place, which expands, dong work on a piston, as shown in the figure below. (a) Is the heat transfer converted directly to work in an isobaric process, or does it go through another form first? Explain your answer. (b) What about in an isothermal process? (c) What about in an adiabatic process (where heat transfer occurred prior to the adiabatic process)?
A certain steel railroad rails 13 yd in length and weighs 70.0 lb/yd How much thermal energy is required to increase the length of such a rail by 3.0 mm? .Note: Assume the steel has the same specific heal as iron.
Check your Understanding Show that QhQh=QcQc for the hypothetical engine of Figure 4.10 The second property to be demonstrated is that all reversible engines operating between the same two reservoirs have the same efficiency. To this, stat with the two engines D and E of Figure 4.10 (a), which are operating between two common heat reservoirs at temperatures Th and Tc . First, assume that D is a reversible engine and that E is a hypothetical irreversible engine that has a higher efficiency than D. If both engines perform the same amount of work W per cycle, it follows from Equation 4.2 that QhQh . It then follows from the first law that QcQc . Figure 4.10 (a) Two uncoupled engines D and E working between the same reservoirs. (b) The engines, With D working reverse. Suppose the cycle of D is so that it operates as a refrigerator, and the two engines are coupled such that the work output of E is used to drive D, as shown in Figure 4.10(b). Since QhQh and QcQc , the net result of each cycle is equivalent to a spontaneous transfer of heat from the cold reservoir to the hot reservoir, a process second law does not allow. The original assumption must therefore be wrong, and it is impossible to construct an irreversible engine such that E is more efficient than the reversible engine D. Now it is quite easy to demonstrate that the efficiencies of all reversible engines operating between the same reservoirs are equal. Suppose that D and E are reversible engines. If they are as shown in Figure 4.10(b), the efficiency of E cannot be greater than the efficiency of D, or second law would violated. If both engines are then reversed, the same reasoning implies that the efficiency of D cannot be greater than the efficiency of E. Combining these results leads to the conclusion that all reversible engines working between same two reservoirs have the same efficiency.
Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 20 rubs, at a distance of 7.50 cm per nub, and with an average frictional force of 40.0 N, what is the temperature increase? The mass of tissues warned is only 0.100 kg, mostly in the palms and fingers.
There are two important isotopes of uranium, U235 and U238 ; these isotopes are nearly identical chemically but have different atomic masses. Only U235 is very useful in nuclear reactors. Separating the isotopes is called uranium enrichment (and is often in the news as of this writing, because of concerns that some countries are enriching uranium with the goal of making nuclear weapons.) One of the techniques for enrichment, gas diffusion, is based on the different molecular speeds of uranium hexafluoride gas, UF6 . (a) The molar masses of U235 and U238F6 are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their typical speeds vrms ? (b) At what temperature would their typical speeds differ by 1.00 m/s? (c) Do your answers in this problem imply that this technique may be difficult?
A physicist makes a cup of instant coffee and notices that, as the coffee cools, its level drops 3.00 mm in the glass cup. Show that this decrease cannot be due to thermal contraction by calculating the decrease in level if the 350 cm3 of coffee is in a 7.00-cm-diameter cup and decreases in temperature from 95.0 to 45.0 . (Most of the drop in level is actually due to escaping bubbles of air.)
Nuclear fusion, the energy solute of Sun, hydrogen bombs, and fusion reactors, occurs much more readily when the average kinetic energy of the atoms is high—that is, at high temperatures. Suppose you want the atoms in your fusion experiment to have average kinetic energies of 6.41014 J . What temperature is needed?
The brakes in a car increase in temperature by T when bringing the car to rest from a speed v. How much greater would T be if the car initially had twice the speed? You may assume the car stops fast enough that no heat transfers out of the brakes.
What does the first law of thermodynamics tell us about the energy of the universe? `
Your house will be empty for a while in cold weather and want to save energy and money. Should you tum the thermostat down to the lowest level that will protect the house from damage such as freezing pipes, or leave it at the normal temperature? (If you don't like coming back to a cold house, imagine that a timer controls the heating system so the house will be warm when you get back.) Explain your answer.
Why don't we operate ocean liners by extracting heat from the ocean or operate airplanes by extracting heat from the atmosphere?
In a study of healthy young men[1], doing 20 push-ups in 1 minute burned an amount of energy per kg that for a 70.0-kg man corresponds to 8.06 calories (kcal). How much would a 70.0-kg man's temperature rise if he did not lose any heat during that time?