Efficiency Definition and 950 Threads

Homework Statement The PV diagram below (I will describe it) shows a cycle for 4.87moels of an ideal gas. The path ab is along an isothermal line. Pressure is in atm and volume in m3 Point a: (.08, 6) Point b: (.24,2) Point c: (.08, 2) Find the ideal and the actual efficiency of...

Homework Statement A 2.0x10^2 g pendulum bob is raised 22cm above its rest position.The bob is released, and it reaches its maximum speed as it passes the rest position. Calculate its maximum speed at that point by applying the law of conservation of energy and assuming that the efficiency...

Homework Statement Joe ascends a small hill from an elevation of 250m to an elevation of 490m. In doing so he expends 2.8x10^5J. If Joe's mass is 75kg what is the efficiency of his climb? Homework Equations W= change in E= change in Ek + change in Ep Ep= mgh Ek= 0.5mv^2...

Homework Statement I am using a 5 kilowatt motor to pump oil to a holding tank which is 20 m above the pump. If the motor is 65% efficient, how many liters of oil can i pump per minute if 1 liter of oil has a mass of 1.30 kg?Homework Equations ?The Attempt at a Solution ?

Hello forum, what is the main difference between max power transfer and max power efficiency? In the case of max power transfer, the goal is to transfer the most energy to the load per unit time (impedance matching). Power is I*V and is about delivering energy very fast... High power...

Homework Statement I'm trying to find an expression for the efficiency of a stirling engine operating with an ideal diatomic gas, and cycling through a volume V and a multiple of its compression ratio, r, Vr. Homework Equations processes: 1-2 isothermal expansion 2-3 isochoric...

A transformer is rated at 2300/230 V, 15 kVA and 50 Hz. Assume that the transformer is operating at 80% p.f., leading and at rated output the secondary terminal voltage is 230 V. The following parameters for the transformer are given: N1 = 1500 turns N2 = 150 turns r1 = 2.7 ohms r2 = 0.024...

We were assigned a problem in class, but because it was on guest lecturer material, I am unclear of which given numbers and what equations to use. I do know I am supposed to use: η=TH-Tc/TH But I am confused as to why I have been given 4 variables ...Please Help! Here is the question [1] You...

Air at 1175 K, 8 bar enters a turbine operating at steady state and expands adiabatically to 1 bar. The isentropic turbine efficiency is 92%. Employing the ideal gas model with k=1.4 for the air, determine (a) the work developed by the turbine, in kJ per kg of air flowing, and (b) the...

The efficiency to which I am referring is the amount of mass converted to energy. I need to find an academic source to cite that fusion is more efficient in this respect than fission. Any sources?

I've read (I think it was on slashdot) that using constant velocity cruise control on your car is much more energy efficient than letting your speed vary. To the point where they said you would want to control your speed to much less than 1 kph. What is the general consensus on this? I'm a...

Given a flexible, inelastic and incompressible string of radius R, how much at most would it shorten from tying an overhand knot in it?

set up 12v bat. to 150w inverter to a tower pc. so i put a amp meter between 12v bat and inverter .times the volts by amps get wattage? then get the wattage of computer using a mains socket(because the inverter produces modified sinewave and my wattage meter may not work...

This is the question that I can't really answer 1. A cycle looks like an ellipse in the T-S diagram. The maximum and minimum temperatures are 1000K and 400K. The maximum and minimum entropies are 0.705 KJ/K and 0.235 Kj/K. Determine a. the heat added per cycle, b. the work produced per...

Hello to you all, Does anyone know if gas engines running on a cogeneration (combined heat & power) mode can achieve electrical efficiency rates as high as 40% as it is...

I am trying to have students build a tester with sourceMeter, lamp, etc. for solar cell efficiency measurement. Could someone give me advice on this project? Thank you very much.

Homework Statement I have attached the question. I'm not really sure how to do this one Homework Equations power = work done/time The Attempt at a Solution Is the turbine efficiency simply the power generation (750kW) divided by the mechanical output (800kW) which is so 750/800 x...

Does the efficiency of a gearbox just reduce the torque output of the motor? Or does it also reduce the speed? For example I have a motor with 100 N*m torque at 100 RPM, it then goes into a gearbox with a 80% efficiency and a 2:1 ratio. So the torque would be 2*100*0.8 Nm and the RPM 100/2...

Hi, I am working on this project that has to involve physics, chemistry and biology. The chemists in my group will be performing an experiment to measure the enthalpy of combustion of three different fuels: alcohol, diesel and petrol. My task as a physicist is to, using their results...

HI, I am wondering what factors go into spectral efficiency and determining and calculating guard bands. Could a tunable antenna or filter within a handset reduce the necessary size of a guard band thereby increasing a networks spectral efficiency? How are guard bands determined/defined and...

Homework Statement A motor produces 1000kW of power, running at 1500rpm. What is the running speed if it runs at 80% power? Homework Equations None that I know of. You can find the torque by the below equation (but again, I don't know how to deal with the 80%) P = \frac{Tn}{9549}...

Does anybody have any numbers for this new discovery? http://web.mit.edu/newsoffice/2011/sun-free-photovoltaics-0728.html How much of the heat is converted into electricity by a standard thermoelectric power plant? And how much of the heat is converted into electricity by this new device?

There are rumors circulating recently on various forums on the internet that a net made of coiled up silver wires increases the efficiency of a gas range when placed on top of the gas burner while fuel is being burned. According to what manufacturers claim, this is done by using the reaction of...

OK so i know it is possible to double the frequency of a light beam by using second harmonic generation by passing the beam through a non-linear crystal; however i am unclear as to the required intensity of light beam that is needed to achieve efficient conversation. Would it be possible to...

If one was to make a pulley to lift something massive like a ship, I am assuming the masses involved of the ship and the counterweight, will mean decreased efficiency due to : 1. Higher friction between in the sheave and axel area. 2. larger cable/robe mass on the longer end (once the pulley...

Would the efficiency gained in an orbital Solar generating facility be mitigated by some/degree of diffusion loss when transmitting, say by microwave. through an atmosphere? Is the rate of efficiency growth in solar panels comparable to that of computer chips? (I think the answer is no). And...

I know people from countries where they just shoot the bad guys. Not much for trials & justice. We spend a lot on housing prisoners in the US. How can the efficiency be improved? Disclaimer: sorry for not creating yet another left-vs-right thread.

Homework Statement If the work put in is 3000j, calculate the useful energy output. [PLAIN]http://www.mkwebman.com/question Load = 1962N Homework Equations VR = Distance covered by effort / Distance covered by load MA = load/effort Efficiency = MA / VR Efficiency = useful...

Thermo Efficiency question! Homework Statement Figure P22.53 represents n mol of an ideal monatomic gas being taken through a cycle that consists of two isothermal processes at temperatures 3Ti and Ti and two constant-volume processes. For each cycle, determine, in terms of n, R, and Ti ...

I note there was talk in the USA about ending the subsidies> There is a link here:- http://www.mcphersonsentinel.com/news/x2108616414/Fight-over-ethanol-brewing-in-D-C Also here:- http://www.afdc.energy.gov/afdc/laws/law/ND/5865 A licensed fuel supplier who blends biodiesel or...

Hello, I am doing a small research investigation into whether Nuclear Fusion will provide a safer and as efficient energy source as current Fission technology. Just interested if anybody has opinions on the topic and what their stance is on Nuclear Fusion, do they think it can work, any...

Homework Statement A reversible refrigerator has a coefficient of performance equal to 9.55 What is its efficiency? Homework Equations COP = Qh/W e = W/Qh The Attempt at a Solution I thought e would simply be 1/9.55 = 0.1047 =0.105 (Sig. fig) This answer was incorrect...

120MJ of heat are used to heat up a 1100kg component from 22oCelsius to 180oCelsius, in 1 hour, prior to heat treatment. If the specific heat capacity of the components material is 500J/kg, calculate the efficiency of the heating process. Please could somone give me the equation that i need...

According to Wikipedia: http://en.wikipedia.org/wiki/Propulsive_efficiency the propulsive efficiency of a rocket is at its peak when the rocket is traveling at the same speed as it is ejecting its exhaust. I understand that, but the graph (and equation) on that Wikipedia page (and elsewhere on...

Does all (i.e. 100%) of the energy generated in the Sun's core via nuclear fusion eventually escape out into space (as photons, neutrinos, ... and umm solar wind?), or is some energy lost to internal processes? Surely the photons must lose energy as they take their long, indirect path from the...

In electron ionisation, how does the electron beam transfer energy to the molecule being ionised? Is it via the interaction of the electric fields of the electrons in the molecule and the beam? If so, what type of interaction? And why is ionisation efficiency of the beam maximised when the...

(Drawing of the setup attached) Background: We conduct electrical tests in our lab on electrical components (circuit breakers, switchgears,etc). In the lab we have a short-circuit Generator that generates the electricity for the tests. The generator is powered by an asynchronous motor...

In a Rankine cycle such as a steam power plant, why does the liquid (water) have be condensed before being reheated first? Isn't the Q just extracted during the condensation stage, wasted into a nearby reservoir, and then re-added in the boiler? Could this water not be fed straight to the...

Hello, An electrical power station situated in Northern Canada uses water to cool the steam as it leaves the turbine. Suggest why the efficiency of the turbine would be greater in winter than in summer: I first started to think in terms of the efficiency equation I have for heat engines...

I was just thinking that if you set something spinning in space it keeps turning, so does this mean once you started an electrical generator turning would you get ‘free’ energy?? Will the force from the magnetic field eventually case the wire to stop spinning?

The excuse given to why energy conversion efficiency even exists, is because that some of the energy is converted to heat. Then how come in electric HEATERS not all the energy is converted to heat? To what does the rest of those 5% is being converted to...

Does the temperature of a solar panel decrease its efficiency?

I have worked this particular problem many times and I keep calculating a power in P(in) that is smaller than calculated power out P(out), resulting in an impossible efficiency of >100%. Is there a mistake in the problem or in my work? Homework Statement A 20 hp, 230 V, 1800 rpm DC...

Homework Statement What is the maximum effciency of a heat engine whose operating tempuratures are 550oC and 365oC? Homework EquationsE=1-Thot/Tcold The Attempt at a SolutionPLEASE HELP! My thinking is that the effciency is equal two one minus the temperature in the hot resavour...

Homework Statement http://i754.photobucket.com/albums/xx183/reddiesel08/Q2.jpg Homework Equations e = 1 - (Tc/Th) (Temp in Kelvins) The Attempt at a Solution e = 1 - (300k/520k) = .42 or 42% No because the engine can only perform 42 J of work for each 100 J of energy. Homework...

Homework Statement I am in grade 11 physics and we are learning efficiency, Eout/Ein.. stuff like that. I just have a few questions about cars: How is efficiency defined in cars and why is it so low in cars? What/How are we improving efficiency? The Attempt at a Solution I think that it...

Homework Statement We have a lab in which there is a ramp with one end on the floor and the other end is on top of a few textbooks. Therefore, it has a slope, and an object is lifted using the ramp. What can we do to this set-up to increase the efficiency, OTHER THAN INCREASING THE HEIGHT...

Homework Statement List a couple factors that make efficiency less than 100%. Homework Equations Efficiency = Eout / Ein Eout = mgh Ein = Work = FD The Attempt at a Solution IDK :\

Homework Statement We have to find the efficiency of a ramp for a lab. We are given an inclined plane, a wooden block and a few masses. We are also given a Newton spring scale. Homework Equations efficiency = (Eout/Ein)*100% Eg = mgh Work = FD The Attempt at a Solution Is the...

I got one device that is small and in ring shape. You have to pass your LPG pipe through the hole and before reaching the stove. It is said that it improves fuel economy by around 25%. The device is Mostly Magnet (can't see inside, but it pretty strong Magnet). Any possibility?