Internal Definition and 957 Threads

hello we know that there is 42% limitation in the efficiency of internal combustion engine, thermodynamically calculated by Carnot and we can never overcome this can someone explain me in few simple words why this is true? also, does this apply to the energy from internal combustion to...

Homework Statement In which of the following cases does the internal energy of the described system increase: (I) A clay ball is dropped and sticks to the ground (II) Hydrogen and oxygen react exothermically to form water (III) A car is driven at constant speed (consider the effect of air...

can anyone suggest me the sites where i can find the methods to improve the efficiency of IC engines?

Would it be possible to build an engine that runs primarily off a petrol but has a steam engine that captures all the heat lost from the combustion (70%) and applies it towards powering the engine? Looking for ideas, opinions and attitudes on whether or not it is a practical idea.

Homework Statement if a potentiometer has driver cell and wire AB ,then an unknown emf (emf<driver cell) is balanced at some length L. does the balance point change if internal resistance of driver cell is changed? Homework Equations V= kl K= potential gradient The Attempt at a...

hello I am interested to know in detail, how internal combustion engines work dynamically, ie. as the demand for speed and torque change what happens exactly? I know that when we want more speed/torque, we push the gas pedal, but what happens exactly between that moment and the increased rpm...

Hi, I heard it was possible if you symmetrically wind a toroid that you can get near total internal confinement of the magnetic field in the axial plane inside the toroid. How is this possible? I imagine a section of a closed loop of wire on the face of the toroid core, yet I still imagine those...

Homework Statement For a single molecule, derive the internal energy U = 3/2kBT In terms of the partition function Z, F = -kBTlnZ Where Z = V(aT)3/2 Homework Equations Thermodynamic identity: δF = -SδT - pδV p = kBT/V S = kB[ln(Z) + 3/2]The Attempt at a Solution U = F + TS δU = δF +...

is it really ok to assume that internal resistance of a cell is absent in a circuit ?

Consider a scenario where a car accelerates along a path, with no air resistance. If we model the car as a particle, we have the following equation: ##ΣW_{ext} = ΔK + ΔU## By question is with regard to the LHS of the equation. It i my understanding that since the engine is a part of the...

Sorry for such a simple question but where do we model the energy going during phase transitions? If I had a mercury thermometer in a pot of water, and I had a 200 degree Celsius heat reservoir in contact with the water, I would see the water temp hold steady during the phase transition...

Homework Statement Students are given some resistors, a battery with internal resistance, and an ammeter. They are asked to determine the emf e and internal resistance of the battery using just this equipment. Working with the circuit shown at right, they insert each resistor into the circuit...

For instance, how to find what internal symmetries a free relativistic lagrangian density has for complex scalar field?

Hello everyone, i need to find reported transfer functions of internal combustion engines for a project, i would appreciate the model of a four cylinder engine. If anyone knows about a book or some article which i can use, please let me know. thank you very much. the topic is related with...

Hello, So I have been struggling to understand internal energy for quite a long time and I hope you will be able to help me get straight with it. The most common definition I find on the internet is "The sum of the kinetic and potential energy of the molecules/atoms in a system" (often gases)...

Hello PF members and guests, I have been working on this concept for 2 years and I wanted to get some input from this forum. I have done a lot of research on oxygen enriched combustion and water injection. Both of these concepts have been tested and proven in experiments and the real world. My...

I understand the main concepts around this topic but I am struggling to find any information about the potential energy involved in the latent heat of fusion. My book defines internal energy as kinetic and potential unlike an ideal gas that is assumed to have just kinetic energy. When a...

Homework Statement Find the conserved Noether current j^\mu of the Dirac Lagrangian L = \bar{\psi} ( i \partial_\mu \gamma^\mu - m ) \psi under the transformation: \psi \rightarrow e^{i \alpha} \psi \,\,\,\,\,\,\,\,\,\, \bar{\psi} \rightarrow e^{-i \alpha} \bar{\psi} Homework Equations...

Homework Statement A glass cup with a mass of 0.1 kg and an initial temperature of 23◦C is filled with 0.3 kgof water at 80◦C A)What is the final temperature of the water and cup? B)How much heat must be added to raise the temperature to 90◦C? C) What is the change in the internal energy of...

In Paul E. Bland's book: Rings and Their Modules, the author defines the external direct sum of a family of $$R$$-modules as follows: Two pages later, Bland defines the internal direct sum of a family of submodules of an $$R$$-module as follows: I note that in the definition of the external...

I am trying to understand the derivation behind the equations for the phase shift incurred when light hits an interface between two lossless dielectrics under total internal reflection (TIR) from what I gathered in S. O. Kasap's Optoelectronics and Photonics. On the final pair of pages...

Homework Statement How can one show/prove that for a beam (hinged supports on both ends) subjected to bending due to a uniformly distributed load over its entire length, the virtual work of internal forces is equal to the virtual work of external forces? Given are the length of the beam (L)...

Homework Statement A 1200-kg car is backing out of a parking space at5.5m/s . The unobservant driver of a 1900-kgpickup truck is coasting through the parking lot at a speed of 4.0m/s and runs straight into the rear bumper of the car. What is the change in internal energy of the two-vehicle...

Hello PF! I have some questions regarding these concepts. First of all, are the following expressions valid for any case? i.e. any kind of process, like isochoric, isobaric. \Delta U = \int C_v \ dT \Delta H = \int C_p \ dT Or is the ΔU expression only valid when dV = 0, and ΔH when dP = 0...

Homework Statement Note: There is an undertilde under every $$\phi$$ Imagine $$ \phi ^t M \phi $$ . M is a symmetric, real and positive matrix. Prove L is invariant: $$ \mathcal{L} = \phi ^t M \phi + \frac{1}{2} \partial_\mu \phi ^t \partial ^\mu \phi $$ Trick: Counting parameters. Homework...

Hi,If the change in U between 2 points (A,B) in a thermodynamic process is always the same despite the path, then please help with the following: Say I have adiabatic conditions so that delta U = Work done only (Q=0) Surely I can go through multiple paths between A+B with increased or decreased...

I am following along with Goldstien's Classical Mechanics Book and I am on page 11. The text is breaking down the total potential energy of a system into two parts: the external conservative forces and the internal conservative forces. My question pertains to the internal forces. Writing the...

I feel like have a chicken and egg type of problem regarding internal resistences because of the following problem: The voltage across a battery with internal resistence is given by the equation EMF-Ir=V Given the voltage across the battery then the voltage in the circuit is V=IR So, if I have...

just how effecient is the internal combustion engine. please tell me(any/all you know/ or can find online), efficency of an average engine, best achieved ever effecincey(ideal scenario), and the maximum theoritical efficency.. i am talking about energy put in vs the amount that is useable.(by...

hey everyone, I am a chemistry student and i am currently working on my final year project, which is to find a chemical difference between canned and bottled coke. one of the aspects I am looking at is CO2 content, so i need a way of measuring the quantity of CO2 in a container. ideally i want...

Homework Statement I understand that voltmeters are supposed to have high internal resistances so that they won't draw much current. However, they are being attached parallel to the resistor anyways and according to Kirchhoff' Law that means the voltage through both the resistor for which we...

Homework Statement Why is the formula for internal resistance for a charging battery v = e + Ir? When the battery is supplying I to the circuit I understand why the terminal voltage, V, equals emf - IR (voltage lost by internal resistance), but if a battery is charging, why is the...

I am reading Chapter 2: Vector Spaces over $$\mathbb{Q}, \mathbb{R} \text{ and } \mathbb{C}$$ of Anthony W. Knapp's book, Basic Algebra. I need some help with some issues regarding Theorem 2.30 (regarding an isomorphism between external and internal direct sums) on pages 59-60. Theorem 2.27...

Homework Statement Suppose light from is moving from water to air. The critical angle be θ i.e. for angle of incidence θ, the angle of refraction is 90°. Refractive index of water wrt air be μ. Suppose the angle of incidence (i) is increased by 1° to θ+1. What happens to the...

Hi Guys! I have a confusion which I hope you can help clear up. The mathematical expression of the first law of thermodynamics can be stated as δu=Q+W where u is the internal energy of the system, Q is the heat added(or taken from) to the system and W is the work done by or on the system. If I...

I'm extremely sorry for not using the template. One of my thermodynamics instructors used this relation to prove another result. I know what to do next and the other steps to end up at the final result but I don't know how this result came. Is it simply mathematics that I'm not aware of, or is...

Apologies for the quick and dirty question, but I was wondering if a computational fluid dynamics analysis of the flow inside a rocket's combustion chamber and nozzle area would be regarded as an analysis of the chamber's/nozzle's internal ballistics. Looking up internal ballistics on wiki, it...

[SIZE="4"]Definition/Summary In thermodynamics, internal energy, U, is the energy associated with the microscopic energies of a system, that is with the energy associated with the random motion of the molecules within a system. More generally, while external energy is energy due to...

A cell supplies a current of 2 Ampere, when it is connected to 5 ohm resistance and supply a current of 1.2 Ampere. If it is connected to resistance of 9 ohm, find EMF(electro motive force) and Internal Resistance

Given that U = (3/2)PV does this mean that ΔU = Δ(3/2)PV for an ideal gas? Hence when finding the change in internal energy using a P-V diagram, can we simply apply this equation instead of using ΔU = Q+W?

Why the kinetic energy is same as internal energy of ideal gas?

Here is an idea I had for a way to deduce the internal structure of an organic object using it's natural radioactivity. The set-up is an array of gamma ray detectors located circularly around the object. By detecting both the position and direction of the gamma rays (obviously impossible to get...

I am reading a book about the interaction between atom and photon. I don't understand the following statement: "for the sake of simplicity, we assume the atom to be infinitely heavy and disregard the external quantum numbers" Q: what is the external (or internal) quantum number of an atom.

Hi everyone. I thought of a question which has been bothering me. It is: Is there a case where energy is added to an ideal gas of constant amount where the energy added will equal the work done by the gas. My thoughts: The energy of an ideal gas is proportional to the temperature. If the...

why total internal reflection happens only when a beam of light travels from a medium with higher index of refraction to a medium with lower index of refraction and not the other way around (i.e from a medium with lower index of refraction to a medium with a higher one)?

Homework Statement An object with kinetic energy K explodes into two pieces, each of which moves with twice the speed of the original object. Compare the internal and center-of-mass energies after the explosion. The Attempt at a Solution Let K1 be the kinetic energy of the main...

Hello Everyone, I am currently re-reading Taylor's Classical Mechanics, in particular, section 4 in chapter 1. He is discussing Newton's Laws, and makes the statement: "A point mass, or particle, is a convenient fiction, an object with mass, but no size, that can move through space but has...

[b]1. Light traveling in air strikes a glass surface with n = 1.48. For what range of angles will total internal reflection occur? [b]2. sinΘc = n2/n1 [b]3. I did this equation with air as n2 and glass as n1 and then got Θc=42.5°. After that I subtracted that from the normal (90°)...

How do I tell if a torque on a system is internal or external before conserving angular momentum? I know that if a force has its reactionary force in the system, then it is an internal force and we can conserve the linear momentum of the system. But I don't know how to recognize a reactionary...

Thermodynamics -- change in internal energy of the system for the path Homework Statement A system comprising of an ideal gas is taken from State a to State b, as shown in Figure 9 below, along th epath acb. 200J of heat flows into the system and 80J of work is done by the system along the...