Questions and Answers of The Physics Energy

In §23.3 we describe the effect of Earth’s axial tilt, or obliquity on insolation and, indirectly, on the seasons. Discuss qualitatively how Earth’s seasons would change if its obliquity were
As a source of black body radiation becomes hotter, the peak in its radiation spectrum moves from the visible to the ultraviolet and beyond. Does this imply that the object can no longer be seen by
The interior of a glass blower’s furnace may contain shelves and other objects of various shapes and colors. As the furnace is heated, objects in the interior become more and more difficult to
Derive the results of Box 21.1 (the last two equations)by using the Schrödinger equation for the time derivative of ψ(x) and ψ∗(x) and integrating by parts.
Think of some physical systems in which energy appears not to be conserved. Can you identify a coupling of the system to external processes that add or remove energy from the system? Can you
According to relativity, the clocks of an object moving with speed v = ?c are slowed down by a factor ? The total(relativistic) energy of the object is given by .mc2? The mean energy of cosmic ray
There is some controversy about the effects of moderately increased radiation levels on ecosystem health. Following the Chernobyl disaster in 1986, and the resulting human evacuation of the
According to Einstein?s theory of relativity, the kinetic energy of a particle with mass m and speed is First, verify that when v kin = ? mv2 . Then compute ? for an electron and an ?-particle
An alternative technology for ultimate disposal of spent nuclear fuel,known as deep borehole disposal, envisions using well-understood drilling technologies to confine SNF in stable geological
The government of Free donia claims to be developing nuclear reactors for peaceful purposes using enriched uranium they have produced from their own isotope separation plants. The IAEA (International
Why do you suppose the author of chose Bordeaux wine for his measurements. Can you suggest other candidates?
What are TENORMs? Discuss some examples such as coal ash,water treatment wastes, or mine tailings. What causes their radioactivity? How significant are the hazards?
Investigate and discuss the physics and public health issues raised by the radium watch-dial painters of the 1920s, the Daghlian criticality accident in 1945, the contamination accident that occurred
Consider the pros and cons of the public health response, including mandatory evacuations, to low levels of environmental radiation following the Fukushima-Daiichi incident. Find estimates of the
Choose one of the Gen IV reactor designs and investigate its advantages and disadvantages. Is there active research and/or development on this design? What is your judgment on its future prospects?
Can you figure out a series of reactions in a neutron-rich environment that would lead from 232Th to 232U? See §20.6.3 for discussion of the role of in possible weaponization of 233U produced 232U
The energy amplifier uses a particle accelerator to feed neutrons into a sub critical reactor. Find suitable sources and give a concise summary of this novel type of reactor, its advantages such as
Some designs for breeder reactors use liquid metals such sodium or lead as a coolant. Discuss some of the advantages and disadvantages of such a coolant.
Explain why the optimal ratio of moderator to fuel is so much larger for a graphite-moderated (infinite, homogeneous) reactor than for a water-moderated reactor at the same enrichment.
Explain why the resonance escape probability grows and the thermal utilization factor falls with increasing ratio of moderator to fuel at fixed enrichment.
Some medical radioisotopes – nuclides that produce specific forms of radiation used for medical purposes – are obtained as fission products from thermal-neutron-induced fission of 235U. A
Check that the nuclides 239Pu, 233U, and 241Pu satisfy the four conditions listed in §18.3.3 for being fissile. A few other actinides Z > 92– nuclei with – produced in reactors are also
234U decays primarily by α-emission. It has rarely been observed to decay by spontaneous fission or by emitting a neon or magnesium nucleus. In what sense are all of these decays different examples
When exposed to a flux of thermal neutrons, most common materials absorb one or more neutrons and many become radioactive (β- -emitters). Explain how this is compatible with energy conservation. Can
The decay chain of 238U is described in some detail in the text. The other naturally occurring heavy nuclide whose decay initiates a decay chain is 232Th. Look up the 232Th decay chain. At what
Radium-226 is a decay product of 238U . 226Ra has a half-life of 1600 years and is found in uranium ores. When it was first discovered and before radioactive decay was well understood, some mineral
Consider the decay chain for 238U shown in Figure 17.13 Why are there -decays, but no electron captures, interspersed among the - decays? U (92) 238 92 Th (90) Ra (88) Rn (86) Po (84) Pb (82) 124
Sketch a curve similar to those of Figure 17.12? for a value of A that results in three isobars that are stable against decay and electron capture. On the basis of the SEMF explain why the number
For small A, where the symmetry energy overwhelms the Coulomb energy, the most stable nuclei with even A have Z = N A/2. For odd–even nuclei in the same range of A, which is more stable, Z = N + 1
Discuss the ways in which the assumptions behind the SEMF may fail when A is very small.
How can the neutron be unstable in free space, but stable when inside a nucleus?
A possible way to evaluate the extent of uranium resources is to build a probabilistic model that includes both known resources and possible unconventional sources of uranium and their relative cost
Research the present cost of fuel for nuclear fission power plants (in $ per MWhe) and compare with the cost of coal and natural gas for conventional fossil fuel power plants. What are the
Investigate the proposed mechanisms for recovering uranium from seawater. What do you think are the prospects for this source of uranium?
It is not hard to balance a (brand new) ordinary pencil vertically upon its eraser. This is a configuration of stable classical equilibrium. Explain why in principle, even under the best of
The scanning tunneling microscope (STM) makes use of quantum tunneling to obtain resolutions down to the scale of individual atoms. Investigate the operating principles and applications of STMs.
Classical systems also decay. The decay or failure rate of many systems follows a bathtub curve. Look up and consider this type of decay and contrast it with the decay pattern of a quantum system.
The tauon τ decays often to a muon μ, which in turn decays to an electron. How many neutrinos, and of which type are produced in this sequence of weak decays.
A baryon frequently encountered in particle physics experiments is known as the Λ (“Lambda”). Its quark content is uds. Sometimes the Λ decays by the process Λ → nγ, where n is a neutron
Two possible nuclear fusion reactions are d + d → 4He + γ and d + d → 4He + p , where d is deuterium, an atom with a nucleus composed of a proton bound to a neutron. 3He and 4He are helium atoms
Gravity is a long-range force proportional to the masses of the interacting bodies. Physicists have long searched to see if there might be a long-range force that is proportional to baryon number.
Physicists searching to see if the proton decays have looked for the reaction. Which of the conservation laws explored in this chapter does this decay violate?
Jet engines use a variant of the Brayton cycle in which the gases are only expanded in the turbine to a pressure sufficient to drive the compressor and the plane’s mechanical and electrical
Explain in words what is going on in the Rankine reheat cycle of Figure 13.16(a) and, referring to the figure, explain the statements made at the end of the discussion in the text about the
The efficiency of the idealized Carnot-like Rankine cycle of Figure 13.12(b) is higher than for fixed but lower than the Carnot limit for 3 T 800 700 z 600 P+ Tvap (p) 500 P- 400 300 4. 2
Describe in words how you would compute the coefficient of performance for an ideal vapor-compression cycle working between temperatures T+ and T- . Assume that you have data on the thermodynamic
A vapor-compression cycle is specified by a closed, counterclockwise loop in the ST-plane. Show that if the loop is executed reversibly then the area of the loop is equal to the net work performed on
There are several other paradigms for simple refrigerators. Research and describe a gas phase Stirling refrigeration cycle or a gas phase Brayton refrigeration cycle. What does the corresponding
The saturation domes for R-134a and isopentane shown in Figures 13.4 and 13.18? are quite asymmetric, with steep (R-134a) or even re curving (isopentane) saturation curves. Water, on the other
Discuss the distinction between an adiabatic and an isentropic process. For example, how can it be that a compressor that works very quickly, allowing negligible heat transfer, can nevertheless
Why is water not a suitable fluid for a vapor-compression kitchen refrigerator? What about for an air conditioner intended to operate between 24 °C and 40 °C?
Use steam table data to estimate accurately the pressure at which water would boil at room temperature (20◦C). Similarly estimate the temperature at which water boils on top of Mt. Everest, where
Under calm, clear conditions during the summer in a temperate climate similar to Boston’s, meteorologists can predict the minimum night time temperature quite accurately by making measurements of
Since the volume parameterizes the points on the phase transition line between liquid and vapor (see Figure 12.7 one could use the density instead of the quality as the thermodynamic variable to
A heat pipe is a device that uses heat conductivity and the large latent heat of phase change to transfer heat very efficiently between two solid bodies. Research the subject. What is the role of
Research what a pressure cooker is and describe the physical principles that make it work.
An insulated cylinder closed by a piston is initially filled with one liter of ice at –20 °C. The piston is pulled out, doubling the volume and initially creating a vacuum above the ice. Describe
What is the role of gravity in boiling heat transfer? Do you think boiling heat transfer would work well on an Earth-orbiting satellite?
A dual cycle attempts to model an SI engine more realistically. It models the combustion process in two steps. First some heat is added at constant volume, then the rest is added at constant
Why would a diesel engine be hard to start in cold weather?
What is the rationale for modeling combustion as a constant pressure process in the Diesel cycle when it was modeled as constant volume in the Otto cycle?
Would you advocate incorporating an Atkinson-like step (isobaric compression after the completion of the power stroke) in a diesel engine? Explain.
Research and summarize the advantages and disadvantages of two stroke engines for personal motor vehicles. What do you see as their future?
An ideal gas is heated to a temperature Tin and allowed to expand a small amount against an external ambient pressure, where the external gas has temperature Tout. We found that the fraction of
Since it is not used up in a Carnot cycle, the gas used as a working fluid could be chosen to optimize the properties of the engine. What advantages would helium (a monatomic gas) have over air in a
The Ericsson engine, invented by Swedish-American inventor John Ericsson in 1833, is based on a cycle that esembles a Stirling cycle except that the isometric steps are replaced by isobaric
An inventor comes to you with a proposal for a new high-tech material containing tiny Stirling engines which exploit the energy difference between the human body and the outside environment. He
In an engine cycle like the one shown in Figure? heat is added over a range of temperatures. Explain why even if it were run reversibly, its efficiency would be less than the Carnot limit defined by
Why does it take more work to compress a gas adiabatically than isothermally from V1 to V2 ? Why does it take more heat to raise the temperature of a gas isobarically (constant pressure) than
The Iron Age began around 1200 BCE, more than 2000 years after the first appearance of bronze in human history. It may come as a surprise, therefore, that the reaction Fe2O3 +3CO → 2Fe +3CO2 is
H2O has a triple point near 0℃, where all three phases, solid (ice),liquid (water), and gas (water vapor), can coexist. So there are three possible phase transitions, solid → liquid (melting),
The heat capacity per molecule of carbon monoxide at constant pressure is shown in Figure? from 175 K to over 5000 K. Explain why c?p ? (7/2)KB for small T and explain its subsequent increase with T.
According to the Sackur–Tetrode formula, the entropy of an ideal monatomic gas grows with the mass of the atoms. Thus the entropy of a volume of argon is much greater than the same volume of helium
An inventor claims to have constructed a device that removes CO2 from the air. It consists of a box with an opening through which the ambient air wafts. The CO2 is separated out by a complex
Living systems are highly ordered and therefore relatively low entropy compared to their surroundings; for example, a kilogram of wood from a pine tree has less entropy then the corresponding masses
Explain why the statements “No cyclic device can transform heat into work without expelling heat to the environment” and “No device can move thermal energy from a low-temperature reservoir to a
In the game of ScrabbleTM, the letters of the English alphabet are inscribed on tiles and a prescribed number of tiles are provided for each letter. Consider an ensemble of ScrabbleTM tiles with
Here is an energy basis state of three electrons in a magnetic field? Are all three of these electrons entangled? What is the probability that a measurement of the first electron?s spin yields +1/2
A suggestion rather than a question: a video recording was made in 1964 of Richard Feynman describing the double slit experiment. It can be found at
We make a big deal about the linearity of quantum mechanics. Is classical mechanics linear? Consider, for example, two solutions to Newton’s laws for motion in Earth’s gravitational field, x1(t)
Sketch the magnitude and direction of the heat flux under the ground driven by annual temperature variations as a function of depth for the four times of the year shown in Figure. 25 20E midsummer 15
A water bed replaces an ordinary mattress with a plastic bag filled with water. If the ambient temperature is below body temperature, water beds must either be heated or covered with a relatively
Although it was not mentioned in the text, Newton’s law of cooling requires that the thermal conductivity k of the object be “high enough,” otherwise the surface of the object will cool below
Look up the effective R-value of wall insulation when the structural support for the wall is either 2 X 4 wood studs or 2 X 4 metal studs. Explain the difference.
People usually discuss their experience of heat and cold in terms of temperature. Closer consideration, however, suggests that it is heat conduction rather than temperature that matters. What do you
The phase diagram for pure iron is shown in Figure 5.13. Iron has three different solid phases, called ?, ?, and ?-iron, with different crystal structures. Discuss the behavior of iron as it is
CO2 is a colorless gas. Why do you suppose the CO2 vapor in Figure 5.8? streaming away from the dry ice appears white? wit
A mixture of sodium and potassium salts is used for energy storage in certain solar energy plant designs. Such a mixture is used in a temperature range between 300 ∘C and 500∘C where it is a
A one liter box containing 0.1 L of liquid water at NTP is lifted from the floor and placed on a table one meter high. How much has the energy of the water changed? How much has its internal energy
Polarized sunglasses are designed to transmit only one polarization of light – the polarization with electric fields vertical – since glare arising from reflections on horizontal snow and water
Suppose an electromagnetic plane wave propagates in a direction perpendicular to a long straight wire. Can you see why a current develops in the wire with the same frequency as the wave?
Explain why the strings that play lower frequency notes on a guitar or violin are generally thicker and less tightly strung than the strings playing higher notes.
Currents produce magnetic fields, and magnetic fields exert forces on currents. When a current flows through a wire, does the magnetic field it produces act to make the wire expand or contract? What
Discuss the statement that Lenz?s law follows from conservation of energy. Consider, for example, the scenario of Figure 3.22(b)? if thesign of eq.? (3.64) were reversed. B = Bot2 B (b)
Most countries provide AC electricity at VRMS ≈ 220–240 V to residential customers. In the US and parts of South America VRMS ≈ 110–120 V is provided. How do resistive losses in
Can you identify the largest component of your personal electric power consumption?
Think of some devices that generally are not run on electrical power. Discuss the reasons why other power sources are favored for these devices.
Regenerative brakes in many hybrid cars such as the Toyota Prius are designed to store the vehicle’s kinetic energy in the battery for later use in acceleration. Such brakes currently can absorb
Using the ideas developed in this chapter, consider the relative energy use of other modes of transport such as airplane or train travel compared to the automobile. Use the internet or other
Is there a minimum energy necessary for transport? Do the laws of physics dictate some minimum energy required to transport, say, 2000 kg of material from Cambridge, Massachusetts to New York? How

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