Internal Definition and 957 Threads

What exactly is the difference between Frensel reflection and total internal reflection with regards to the efficiency of an LED? Do they both occur at the semiconductor/ air interface? I am a bit confused, thanks for the help.

Hi I am struggling to see how the relation: (df:U)(dh:V)-(dh:V)(df:V) (1) can be rewritten as: U(fdh:v)-V(fdh:U)-fdh:[U,V] (2) I have tried expanding (1) out by making a scalar vector product of Udh:V but i don't think that is right and i am just not sure how best to proceed. It was...

[FONT=arial]Problem: Let A, B, C be three non-collinear points. Let D, E, F be points on the respective interiors of segments BC, AC and AB. Let θ, φ and ψ be the measures of the respective angles ∠BFC, ∠CDA and ∠AEB. Prove IAS(ABC) < θ +φ + ψ < 540 - IAS(ABC).(IAS means internal angle sum). Now...

HI Assume we have a point charge in the center of a shell, now the inside inner wall will get an opposite charge and the outer side of the shell will have the same charge as the point charge. Since we have a charge on the out side, how isn't there any fields outside ?? how are we...

Six grams of water changes from liquid to vapor at a pressure of one atmosphere. In the process, the volume changes from 0.9 cm^3 to2387 cm^3. The latent heat of vaporization of water is 2.26 × 10^6 J/kg Find the increase in internal energy of the water. Answer in units of J When i...

A general thermo question... for the function describing internal energy U(S,V,A,N) U=TS-PV+γA+μN please explain how the total differential is dU=TdS-PdV+γdA+μdN (for a one component system) Basically why is dT=dP=dγ=dμ=0? Is it because they are intensive or potentials...

Hello I may well be all wrong about this but I am trying to understand from a microscopic point of view why Entropy is a concave function of internal energy. I found this in the following .pdf: http://physics.technion.ac.il/ckfinder/userfiles/files/avron/thermodynamics_potentials.pdf I...

Homework Statement Power supply of EMF = E and internal resistance of R. Need E and R. This is connected to resistor of 10'000 Ohm. The current drawn from the power supply is 0.91A. A voltmeter of internal resistance 10'000 Ohm is connected in parallel to the resistor. The voltmeter reads...

For ideal gas , can I assume Cv dT = nkT (3/2) , thank you

Hi, Firstly, I'd like to thank PhysicsForums and its members for helping me during my last couple of visits (around 7 months ago). With your help I managed to achieve an A at AS Physics (a UK exam)! I am doing some basic concepts on internal energy etc and I came across the following...

G, H, K are groups. G is finite. GxH is isomorphic to GxK. Prove H is isomorphic to K. Give an example to show that this does not hold when G is infinite. The counter example when G is infinite is Rx{0} and RxR (R - real numbers) I'm having trouble Proving the main part of the question. I...

Homework Statement Assume nitrogen gas (N2) is an ideal gas. n = 7.57 moles of N2 gas are heated isobarically (at constant pressure) from temperature To = 18.6 oC to temperature Tf = 50.9 oC. Find: c) ΔIE, the change in internal energy of the N2 gas Homework Equations Change in IE...

[b]1. Steam into a steam turbine at 7 MPa and 500 deg C. The turbine has an internal efficiency of 90 %. The steam exhausts at 20 kPa. 1) What is the exhaust enthalpy? 2) What is turbine work? 3) What is the quality of the exhaust steam? This is a question I got on a 2nd class boilers...

Homework Statement A 0.75-kg block slides on a rough horizontal table top. Just before it hits a horizontal ideal spring its speed is 3.5m/s. It compresses the spring 5.7 cm before coming to rest. If the spring constant is 1200N/m, the internal energy of the block and the table top must...

Homework Statement A fixed mass of gas is trapped in a metal cylinder by a movable piston. The piston is moved outwards slowly. The volume of gas increases but the internal energy is unchanged. What happens to the pressure and to the temperature of the gas? Homework Equations none The...

why cannot hydrogen and oxygen not used in internal combution engine as fuel? it would be pollution free.

Homework Statement A thermally isolated container is filled with 2.3 mol of an ideal gas at T = 0°C.The gas is then compressed from 1.9 m3 to 0.3 m3. What is the final internal energy U of the gas? (Assume the process occurs at constant pressure.) Homework Equations U=3/2nRT U=Q+W W=pΔV...

The temperature of 2 kg of N2 changes from 300 K to 1000 K. Calculate the change of its internal energy during this process, assuming the ideal gas behavior, in two different methods: (1) Using constant heat capacity (2) Using the enthalpy function ı have to solve this question but ı...

Homework Statement The internal energy of a perfect gas does not change when the gas undergoes isothermal expansion. What is the change in enthalpy? Homework Equations H=U+PV The Attempt at a Solution The answer is 0 Since U, the internal energy, doesn't change, I assumed that...

A liquid contained in an adiabatic container is shaked vigorously so that it its temp. Increases. The heat capacity for the liquid is given, the rise in temp. Is given. According to the first law of thermo, dQ=dW + dU here dQ is 0. Asked, is to find the work done on the system, i.e...

Homework Statement For example in the problem if we have a volume of 10L at 15 degrees Celsius, and there is initially 100Pascals pressure, what would the final pressure be if we double the Internal Energy? Homework Equations U=3/2nRT The Attempt at a Solution I though pressure was...

If the temperature is kept constant,what happens to internal energy if the pressure is increased in piston?

A moving-coil meter, with internal resistance... Homework Statement A moving-coil meter, with internal resistance Rmeter = 15 Ω produces full-scale deflection for a current of 13 mA. Design a voltmeter, as shown below, which can measure voltages in the range 0 - 14 V. What is the required...

Homework Statement I am taking a class in circuit analysis and am trying to measure the internal resistance of the Radio Shack multimeter. The internal resistance (unknown) is R_x. A battery (with voltage V_s) is available along with a resistor R that has the same order of magnitude of R_x...

What is typical internal resistance of a voltage meter on a handheld analog multimeter, and also what is typical resistance on its ammeter?

Hi All, I am wondering if there is any way to monitor internal corrosion in pipelines (without using pigs and interrupting the flow)? May be ultrasound waves could be used for this purpose, however I am not sure if it would be able to give a clear picture of extent of corrosion. Thanks...

In a heat transfer with internal heat generation what does the term "internal heat generation" mean? Is that applicable only if a body itself produces some heat (Like current carrying wires,nuclear fuel rods etc) Or if i have a two cylinders one within another,and if inner cylinder is heated...

Homework Statement A resistor with resistance R is connected to a battery that has emf 15.0[V] and internal resistance r = 0.38[Ω]. For what two values of R will the power dissipated in the resistor be 78.0 W? Homework Equations P=I2R=(ε2/(R+r)2)R The Attempt at a Solution...

Fair warning: This is more chemistry than physics but I know that thermodynamics and heat and work are all covered in General Physics but I'll post in the Other Science forum too. 1. Assume that one mole of H2O(g) condenses to H2O(l) at 1.00atm and 95 Celcius. Calculate q, w, ΔH, ΔS of the...

What is the origin of the internal magnetic field in an atom (which gives rise to spin-orbit interaction in an electron). The energy associated with this field is calculated using the reference frame of the electron and then returning back to the nucleus reference frame (thomas precision). But...

Calculate the internal reactions for the member shown at the sections indicated; picture attached with FBD's I have the V & F forces correct but my moments are off. Can you point me in the right direction here? V M-M = 2k F M-M =-0.5k V N-N = -2k F N-N = 0.5k M M-M = -10k (2) +...

Homework Statement Assuming each battery has internal resistance r = 1.0 Ω, determine the magnitudes and directions of the currents through each resistor shown in the following figure. The batteries have emfs of 1 = 9.0 V and 2 = 12.0 V and the resistors have values of R1 = 15 Ω, R2 = 20 Ω...

"In 97.7% of disintegrations 123I decays by electron capture to an excited state of 123Te, which has an energy of 159keV. Gamma rays of energy 159keV are emitted following 82.9% of decays. What's the internal conversion coefficient for this de-excitation?" I know that a=Ne/Ny(gamma), but...

Suppose in a piston in which there is a gas, the gas exerts pressure P on surroundings, whereas the surrounding exerts a pressure P[ext] on the gas. In order for the gas to expand, P must be greater than P[ext]. So far I understand. Suppose initially that P>P[ext] and the gas expands until...

Anyone knows what is the approx. internal resistance of a lead battery, say, 12V, 20Ah. Thanks

Calculating the internal energy of gasoline is fairly simple, because it wouldn't vary much with temperature or pressure. For hydrogen, though, it would vary significantly with each. What sort of ranges would we be looking at? I'm curious if it would be possible to get the same amount of...

Hi, Does battery internal resistance obey the general resistance-temperature rule? For metal, resistance usually increases with temperature (see wikipedia). For batteries however, its internal resistance decreases with temperature (also see wikipedia). Could anyone explain the...

Homework Statement A battery has an emf of 6v. The battery is connected in series with an ammeter and a voltmeter.If a certain resistor is connected in parallel with the voltmeter,the voltmeter reading decreases by a factor of 3,and the ammeter reading increases by the sme factor. What is...

How can wave optics explain total internal reflection?

I know this question has been done to death and I have had a look through past questions on this forum and others but I can't find anything that is helpful to this particular question! Homework Statement An ideal monatomic gas expands reversibly at a fixed pressure of 10^5 Pa from a...

Homework Statement In the attachment below, a ray of light undergoes total internal reflection in an optical fiber such that the angle θ between the ray and the interface is 47°. Assuming the fiber is surrounded by air, what is the minimum index of refraction necessary for this to occur...

When we talk about Snell's law, and total internal reflection in particular, we usually will draw diagrams as if light is coming off a point in a single, straight line (that bends at an interface, of course). My question is, though, how does this light behave when it's coming off an extended...

hi i have this pV-diagram(ideal gas) and i am supposed to say something about the heat, internal energy and work transferred and done on these different paths( i have to bring them in an order like). i do not know how to do this, as this is a pV diagram and these paths are not further...

Does total internal reflection happen with all types of waves, or just electromagnetic ones?

Changes in the internal structure during a "Topological transform" Is there any field of topology which deals with the changes in internal structure of an object when it undergoes topological transform? If I'm transforming a cube into a sphere, is there any 'field of topology' which analyze the...

Hi all, So quarks are given fractional charges, which then add to the total charge of the particle they constitute. My question is if the electromagnetic forces between quarks are taken into account? I was thinking that such things might be automatically taken care of via Feynman diagrams...

Internal symmetries of the SM -U(1), SU(2), SU(3)- are usually said to belong to abstract spaces unrelated to spacetime symmetries, have there been many attempts to relate internal symmetries to spacetime symmetries, and if so how far have they gotten?

hi all, i have a confusion about the internal energy change and work done in a isobaric system... suppose i want to find the delQ in isobaric system in terms of P & V...now i may assume the delW part would be pdv=p(V2-V1)...as i m compressing the gas... but what happens to the du? and is the...

[b]1. We have some gas in a container at high pressure. The volume of the container is 469 cm^3. The pressure of the gas is 2.52*10^5 Pa. We allow the gas to expand at a constant temperature until its pressure is equal to the atmospheric pressure, which at the time is .857*10^5 Pa. (a) Find...

hi everyone, in thermodynamics, when we calculate the heat capacity in constant volume, we assume Cv=dQ/dT.. well, but at isothermal condition suddenly they came up with Cv=dU/dT... so i am getting stuck with this concept how they replace dQ with dU? i know U= internal energy is only a...