Efficiency Definition and 901 Threads

I've calculated the efficiency of the Stirling cycle like \eta=\frac{R(T_H-T_L)\ln\left(V_2/V_1\right)}{RT_H\ln\left(V_2/V_1\right)+C_{mV}(T_H-T_L)} Where V_2>1. It's also derived http://www.pha.jhu.edu/~broholm/l39/node5.html" . But my ("Highschool", or secondary school) teacher says...

Calculate the ideal (Carnot) efficiency of a heat engine operating between 23.0 degrees and 515 degrees. How much heat would be rejected by the engine if 1.00 x 10^6 calories were taken from the high temperature resivoir. Would you just use e=1-(T(c)/T(H))? And for the second part i don't...

A coal fired plant generates 700 MW of electrical power. The plant uses 5.8 * 10^6 kg of coal each day. The heat combustion of cal is 3.3 * 10^7 J/kg. The steam that drives the turbines is at a temperature of 320 C, and the exhaust water is at 45 C. Note: 700 MW= 7.0 * 10^8 J/s = 6.0 * 10^13...

Please help with the following question, completely lost: The behavior of a four stroke gasoline engine can be approximated by the so-called Otto cycle. The process is as follows (6 steps): 1) Isobaric Intake (from V=0) at atmospheric pressure up to volume V1 (maximal volume)...

sprinkler efficiency (urgent :)) Ok, I have an exam on monday and both my lecturers and tutor have gone walkabouts. So you guys are my last resort. Thanks. :) Anyway: Water is discharged from a a garden sprinkler from two nozzles and opposite ends of an arm. Its the type that spins around...

If anyone out there is able to give a brief overview of how oil is used as an energy source, I would really appreciate it! Nothing too fancy, I just need to know the basics of how it works and how to find its efficiency. Thanks so much.

A farmer uses a pump to lift water from a river to a arable land who lies 5.0m higher than the river. The pump exhaust an electrical effect of 1.0kW but only 65% is used to do the lifting. ok A) I have resolved the lifting work is 0,65*60 = 39kJ But B) is harder,,,, how much water is pumped...

Hey, this is just a quick question on the quantum efficiency of CCDs. First of all, you are given the quantum efficiency of the CCD and the throughput value of the filter. So do you just multiply the throughput by the original quantum efficiency to obtain the quantum efficiency of the...

www.mybiopro.com/savefuel ... can anyone tell me if you can actually increase fuel efficiency by resonating gas, and can someone maybe send me some links (if you know any) that explain how these things actually resonate the fuel without any external power source. AND if they don't have a power...

What habits and technology can we adopt to reduce personal energy consumption?

I have been working on this problem for 2 days and can't seem to figure it out.. A 1500hp pump throws a jet of water 125 m into the air. (a) With what speed does the water leave the mouth of the fountain. (b) If the overall efficiency is 60%, how many liters of water per minute are thrown...

I've been reading a lot lately about how people have vehicles that have a really good fuel economy. Some even seem considerably better than what the normal car can get. It makes me wonder if there are modifications being done to achieve this. I drive a 2000 GMC Sierra Z-71 5.3L truck...

If the gunpowder in a gun is detonated in a chamber consisting of compressed air such that the top of the chamber is formed by the bullet, wouldn't the efficiency of energy extraction from the gunpowder increase as the pressure ratio will be much higher? Would such a bullet be able to achieve...

I read in a science question/answer book that it is takes as much energy to turn on a fluorescent light as it doesn to run it for 1 hour. So if this is true, it would mean that if you plan on using the light again within an hour, it is more efficient to leave it on, rather than turning it off...

These are some problems I am having difficulty with, the first problem I got an answer but I am unsure if it is correct and the others I have no clue. If you can step by step how to do them it would be greatly appericated. A 12 kg. fish swimming at a velocity of 3 m/s swallows an...

In brayton cycle, the initial temperature and pressure before compression is less than the final temperature and pressure after work has been done by the hot gases. If the final temperature and pressure is made less than the initial temperature and pressure, would it reduce the efficiency of...

A steam plant burns 6000 kg/hr coal, heat value 34 MJ/kg 18kg of air at 15 C is used/kg coal burned. Flue gas tem is 250 C. 46000 L/min cooling water used for condenser - inlet at 8 C and outlet 20 C Find max work done kW/h and thermal efficiency. I tried the following formula ...

Dear people of Physics Forums, I would like to have your opinion about the following problem: Suppose we are interested to evaluate the average efficiency ( e ) of an infinite series of carnot cycles. The temperature of the hot reservoir of each carnot Cycle of the series, Ta, is at 990K, but...

Does a pulley have more efficiency if it has just one of those cirgular thingies http://upload.wikimedia.org/wikipedia/en/8/8f/Pulley_class2.PNG or more http://www.kirkwood.k12.mo.us/parent_student/khs/BartinJ/four_pulley.gif An explanation would be helpful as well.

An engine with an output of 150W has an efficiency of 25%. It works at 10 cycles/s. A. How much work is done in each cycle? work=power(delta t) = 150 W * 1s = 150 J work =15.0 J per cycle **got part A correct B. How much heat is given off in each cycle? delta...

I'm not to sure how to do this question. Q. A 4MBq gamma source emitting 5 KeV photons is held at a distance of 5 cm from the end window of a detector. The diameter of the detector window is 3.5 cm, and the quantum detection efficiency of the detector is 15%. i)What is the geometric...

What is the approx. efficiency of the conversion of light energy to chemical energy in photosynthesis? a. 100% b. 95% c. 15% d. 1% I doubt that it is 100%. Is it 15%? I did a search, and I read that the efficiency is 13% for CO2 fixation using solar radiation. I don't know if this is...

Suppose that you want to freeze 1 kg of water for a party, and only have 5 minutes to do it. Relying on nothing but your keen physical abilities, a dixie cup, duct tape and a piece of string, you manage to build a refrigerator unit which can do the job. The temperature inside the refrigeration...

I have a boiler which for a certain period of the year has a spesific boiler efficiency, let's call it A. For another period of the year the boiler isn't used that much, and so it now has a different boiler efficiency B for this period. How do I find the overall efficiency for the whole year...

I know it's 35% but can someone provide a link?

I know the leg efficiency for humans is 0.35 (or 35%) but I need a source to corroborate it. Are there any available links at anyone's disposal that I may use to cite?

Hi all, I've been doing a lot of research recently, but am still struggling to do a good hypothesis for my experiment. The experiment is to find the efficiency of a ramp. I will be changing the height of the ramp and will be measuring the force required to lift a bucket with a total mass...

Any car buffs here? Just trying to make sure that I understand (because I am currently confused) about how to convert calculations of air between mass and volume. The problem I am trying to solve is calculating the Volumetric Efficiency of an engine at specific points in time. I have a...

How did British engineer John Smeaton measure the efficiency of an overshot waterwheel? I am doing an experiment with overshot waterwheels to find their efficiency, and found that John Smeaton measured their efficiency at about 65%. However I have no idea how he got this number, and I cannot...

im curently learnin thermodynamics at school and the teacher makes it sooo boring... but i love physics nd its very interestin in the books such as resnick halliday... well neways... there was a problem.. in resnick... trucker carryin certain volume of diesel travels to a place where temperature...

how can I find efficiency of heat engine operating between two differenct temperatures?

Ok I have this car powered by the wind. In order to caclucalte the efficiency I would like to compare the maximum energy possible to be taken out of the wind(air) compared to the actual energy output 1/2mv^2. Is this viable? And could someone give a formula for wind energy? Also to create...

Hello, I've been thinking about why (elementary) transformer efficiency drops drastically at very low frequencies. I know hysteresis effects play a major role in reducing efficiency at high frequencies, but why low? I realize that as we reduce the frequency of the emf, we're making the...

modern steam car If found this website on steam cars http://www.geocities.com/MotorCity/Shop/3589/ The author seems very down to earth, and his project worthwhile. I wondered as he mentions, about the production costs of such vehicles, the engines would surly be cheap to produce en mass...

What is efficiency of a crane that uses 5.10 x 10 to the fifth power of energy to lift 1000kg a vertical height of 32.0 m ? geez what formula do i use lol i tried using the heat energy formula but to no avail T_T someone offer help lol like what formula do i use?

Seriously Stuck.. A coal fired plant generates 600MW of electric power. The plant uses 4.8 x 10^6 kg of coal a day. The heat of combustion of coal is 3.3 x 10^7 J/kg. The steam that drives the turbines is at a temperature of 573K, and the exhaust water is 310K. 1.) What is the overall...

heat system efficiency?? So lost..so what am i suppose to do?? 'An engine absorbs 400J of heat and does 120J of work in each cycle' a)what is its efficiency? b)how much heat is rejected in each cycle?

Hi everyone, This is a simple question which has probably already been solved by someone, but I couldn't find it in the research anywhere, so maybe somebody here can help. First of all, say we have a program which uses a new algorithm that outputs the nth prime when you input n, I call it...

Hi, I am stuck on the question, I don't require the solution, just how to get started. A power plant's electrical output is 750MW. Cooling water at 15oC flows through the plant at 2.8x10^4 litres/sec and its temperature by 8.5oC. Assuming the plants only energy loss is to the cooling water...

I find in Martin Rees "Just Six Numbers" that hydrogen undergoes fusion to helium with a mass energy conversion of .007, that is, the mass of the helium formed is less than the mass of the hydrogen by this ratio. Is it a coincidence that this number is the same as the fine structure...

I was wondering about the benefits of building a biplane for an aero-design contest. The rules state a particular wingspan limit, but there is no limit on number of wings. There is also a limit on the type of engine. The plane that’s able to lift the heaviest payload and still be controllable...

The boiler of a steam engine produces steam at a temperature of 500C. The engine exhausts its waste heat into the atmosphere where the temperature is 20C. Assuming that the efficiency of an engine can never be greater than that of a Carnot engine, what is the limiting efficiency of this engine...

I'm sure everybody has heard all the stories about high mileage carburators and the oil companies etc. But why has this problem not been solved? Approximately two thirds of the fuel we burn in our cars goes out the tail pipe. I've read that someone has used catalytic cracking to breakdown the...

i am designing an armor in my head (along with hundreds of other things) and i want to know specifics about cooling systems. I've decided on a coolant system pumped by feet/arm movements/etc but i need to know: how effective are such systems? specifically, how long would they last, how cold can...

I'm having trouble with proving the following question. Can someone please help, please. (1) Prove that if you had a heat engine whose efficiency was better than the ideal value (4.5) you could hook it up to an ordinary Carnot refrigerator to make a refrigeratior that requires no work...

Have any of you heard of the hydrosonic pump? It is an "over unity" device that actually works. It is said to produce about 1/3 more energy in heat than it requires in electricity to produce. It is not a perpetual motion machine because it does not produce enough energy to run itself...

when i am calculating the eggiciency of a heat engine i have to convert the celicus to kelvis and used this formula eff = 1-(T cold/T hot)*100 fro example 302C = 593K 610C = 883K eff = 1-593/883 = about 32.8% efficient right ? thanks joe

A heat engine has an efficiency of 25.0% and its heat input is 600J per cycle from the high-temperature reservoir. What is the rate of heat output to the low-temperature reservoir per cycle? E=(Qh-Qc)/Qh .25=(600J-Qc)/600J Qc=450J book has the answer as 800J. How are they getting 800J...

This is a thread to discuss the efficiency of magnetic levetation a la monorails. I really don't know how it would compare to the traditional surface contact-based transportation. If you have some knowledge on this or know where to find it, please speak up. The lack of friction would...

One kg of fat is equivalent to about 30 MJ of energy. The efficiency of converting fat to mechanical energu is about 20%. a. Suppose you lift a mass of 12kg 2.0m vertically, 500 times how much work do you do? (Assume that the work done by mass on you is disepated as heat to the surroundings)...