Efficiency Definition and 901 Threads

Does anyone else struggle with the loss of time? Each day I end up wasting at least 4-5 hours to unproductive causes[activities for which I did not allot my time]. Like today at 6 PM, I decided not to watch movie and do some work. But, for some unknown crazy reasons, I end up wasting 4 hours...

My physics professor posed that question to us a while back, and he never gave us the answer. I tried solving it but I had no idea what units to convert it too. Does anyone have any ideas as to what the answer may possibly be?

the toy car gains energy by pushin down the "head" of the "driver" and is powered by a spring that powers the wheels. at different heights, it has different spring constant. I mean the slope's angles are changed at different periods of the experiment. I am unable to work out the spring constant...

Why can't we improve the efficiency (miles/gallon) of ICE autos? It seems to me there are two areas that can be used to add efficiency: 1) Heat recovery with some form of a "bottoming cycle" to generate additional torque or electricity from heat lost in the radiator, and 2) Breaking...

Homework Statement An 8.5 kg elevator is pulled at a constant velocity of 1.0 m/s by a 10.0 kW motor. Calculate the efficiency of the motor. Homework Equations W = change in E = Fd e = Work out/Work in * 100 = energy out/energy in *100 Epotential = mgh Ekinetic = 1/2mv^2...

I see a lot of references to the 'efficiency' of the Tesla turbine, however, I can't find any actual data. Does anyone have a handle on actual achievable efficiencies of the tesla turbine?

As I fine tune our VAV HVAC system (506,000 sq.ft. facility), we'd like to determine the effectiveness of our adjustments over time. As we both heat and cool portions of the building at the same time (electric VAV reheat), we need to apply degree days to the analysis. How is that done...

how efficiently do we turn our food into energy? I have been kind of wondering if in the future it might be possible, and, a good idea to use biological processes to make energy out of food for energy? I know we can already process plants and extract sugar to make ethinol, or oil for...

Homework Statement a power plant generates 2000MW of heat energy from nuclear reactions in the reactors core. this energy is used to boil water and produce hight pressure steam at 300degreeC. the steam spins a turbine, which produces 700MW of electric power, then the steam is condensed and...

Hey guys, I have been given that the isentropic efficiency of a nozzle = 90%. Inlet condictions are: 5MPa and 550°C and exit: 100kPa. Now \eta_{n}(h_{i} - h_{0}) = V^{2}_{i}/2 h(o) - h(i) is the enthalpy drop across the turbine. Now next they say that s(o) = s(i). Now how can the entropy at...

Homework Statement First of all I apologise if this is in the wrong place. Anyway we have been given the task of finding out the efficiency of a solar panel, where energy from a light bulb is used to heat the water in the panel. I was just wondering if someone would just check that my...

how can we increase the efficiency of brakes in an ATV specially? I'm working on an ATV these days n plan to use disc brakes... i read about cross-linked braking circuit...can someone tell me how efficient is this system...should i try to employ it?iv heard it has been used in Audi before...can...

Homework Statement The thermal efficiency of a refrigerator is determined by the coefficient of performance , which is defined as the ratio of the amount of heat removed to the input of mechanical work needed for operation, or K=Q_c/W_in An air conditioner operates exactly as a...

[SOLVED] Thermal efficiency of a coal powered power station Homework Statement A company plans to build a coal powered plant for eletricity generation. The coal is to be burnt ina heat engine designed to maintain a hot resovoir temp Th, and a cold resovoir of 120 degs celcius. What is the...

Howdy, I'm no physicist, but I am a scientist by trade and some basic physics questions always bug me because I don't have any bases of understanding of the concepts. I apologize if these questions seem a bit abstract: Suppose an event occurs that causes the emission of EM radiation (for...

What is the typical efficiency (as a function of muon energy and/or rapidity) of a moun detector at an accelerator experiment? More specifically I would like to know about the lower energy treshold: E.g. if a muon with energy of just some few GeV is produced in the collision process, what is...

My science teacher told me the human body is only 38% efficient at converting energy, if we were able to to convert energy at 100% efficency we would be "Super Humans"? As in heightened senses, amazing endurance, incredible speed or we would just die or something?

Does anybody know why thorium is better than uranium as far as heat transfer is concerned?

Homework Statement Which of the following statements about a Carnot engine is true? a) Any Carnot engine has an efficiency of 100% b) Irreversible energies have the greatest possible efficiency. c) Heat can spontaneously flow from a cold reservoir to a hotter reservoir. d) If a process is...

Hi there, As part of my A2 physics coursework investigation, i want to calculate the efficiency of an aluminium canister modeled as a solar collector. The basic set up of the apparatus is: - Lamp (40W light bulb) at a fixed distance of 5cm away from the aluminium canister (which is...

Hi Could anyone help me with this? How would i go about calculating the thermal efficiency of a heat engine with four processes? I am thinking of moddeling it on the Otto or Diesel Cycle. The data i have is. Temp @ State/Process 1 Specific Gas Constant Specific Heat Capacity...

I am to design a laboratory experiment to compare the energy conversion rates of two standard methods for solar energy to be 'trapped' for domestic use. See below*. I need to compare the two systems and find out which is more efficient. The energy source should be a standard 150W light bulb...

I want to settle an ongoing debate that has plagued some car forums I have been on for years. Scenario: -A Rear wheel drive car; 1996 M3 @210whp, against an AWD 60/40 transfer case ratio 2004 STi @220ish AWHP. -0-100mph race the STi wins (AWD duh) -if started at 100-150mph the M3 wins (RWD...

Attached is a graph of a system that has undergone heating/cooling, expansion/compression. The question is: Suppose now that this system is being used as a heat engine, to convert the heat added into mechanical work. Estimate the efficiency of this engine. I'm confused...in this system, there...

This is an attempt to calculate the efficiency of a modern gasoline engine (Volkswagen's 1.6 litre FSI). The result seems too good to be true. Please let me know if there is any error. At a constant 100 km/h on a flat motorway, the consumption of my car reads 5.7 l/100 km. The engine revs...

Although I generally understand how a siphon works, I am wondering if a siphon would work in a vacuum or in a pressurized enviroment?

Alright. I have a physics project due in about 10 days and I am not quite sure how to go about it. I have to make a "vehicle" move as efficiently as possible. I can only use 1 Joule of potentional gravitational energy per the equation mgh. The only specifications of the vehicle are that it is...

[SOLVED] Nuclear Powerplant Efficiency Homework Statement A nuclear power plant operates at 78% of its maximum theoretical (Carnot) efficiency between temperatures of 540°C and 330°C. If the plant produces electric energy at the rate of 1.3 GW, how much exhaust heat is discharged per hour...

What does the efficiency bell curve of a good power supply look like? Should the curve peak out at typical load?

Homework Statement A 3250 km aircraft takes 12.5 minutes to achieve its cruising altitude of 10 km and cruising speed of 850 km/h. If the plane's engines deliver, on the average, 1500 hp of power during this time, what is the efficiency of the engines? Homework Equations Efficiency =...

My question is why the power efficiency % goes down with Voltage in step down transformers. The #of coils is less, therefore internal resistance is less too. Why the loss of efficiency in power? I hope someone can help

Is it possible to show that the maximum efficiency for a heat engine is given by \eta = 1 - \frac{T_c}{T_h} where T_c is the temperature of the cold sink and T_c is the temperature of the warm sink? In other words: How do I prove that a engine run by a Carnot cycle is the most efficient engine?

Fill the tanks with the same type of gas. Determine how many miles they travel. Fill the tanks again. Determine the gas consumed by each. Calculate the equivalent amount of energy spent by each car (I need the equivalent amount of energy per gallon of gas). Calculate the energy per mile consumed...

Homework Statement Each second, a nuclear power plant generates 2000 MJ of thermal energy from nuclear reactions in the reactors core. This energy is used to boil water and produce high pressure steam at 573 Kelvins, the steam spins a turbine, which produces 700 MJ of electric power, then the...

A non-ideal voltage source supplies current of 250mA to load resistance of 3.3kOhms. What is the magnitude of the source voltage if the power efficiency is 94%. Also calculate the value of the additional resistance which must be added to the circuit to limit the current drawn from the supply...

A coal power plant with three power generators is used to power a small city. If each generator uses 1.22 X 10^8 J of chemical energy in the coal every hour, and the average annual energy consumption of the city is 1.61 X 10^12 J. What is the efficiency of the generators? (Assume the...

Hi all. I'm new to the forums and am looking forward to contributing. At the moment, I'm having trouble figuring out this chemistry problem i have for homework. The United State's gas and oil supplies are shrinking and are now using the electrolysis of water as a source of energy. The...

What processes, mechanisms or basic physics could experience an increase in efficiency best for world society?

Dear peeps, i am currently facing a problem here. i am tasked to place PV cells within an area and maximize the efficiency of PV cell by focusing sunlight on the cell itself. I am wondering if it is possible. I am thinking of placing 3 cells in a U shape. 1 at the bottom facing up and 2 at the...

Extraction efficiency problem PLease help... Homework Statement [FONT="Comic Sans MS"][SIZE="4"]The distribution coefficient, k = (conc. in CH2Cl2/conc in H2O), between dichloromethane and water for solute A is 7.3. What weight of A would be removed from a solution of 10 g of A in 100...

I'm doing something for a science fair experiment and I'm trying to compare a catapult to a trebuchet. i will be comparing range, accuracy, and efficiency. But i don't know the equation to find efficiency of each siege wepaon. both of these medieval wepaons will be tabletop size som they won't...

[SOLVED] Power plant Hi! Here i have a problem : A power plant generates 400 MW of electric power.It has an effieciency of 40%. a) At what rate does it dissipate heat? b)If the waste heat is carried away by a river, and the temperature rise of the river must not exceed 3°C, what flow rate is...

In an ordinary electrical appliance they usually tell you the wattage of it on a tag. Does the wattage include all power loss throughout the whole circuit or does it only tell you the amount of power dissipated at the main components. For example say I have a flashlight. Would the wattage on the...

I was thinking in the last weeks about electric cars and thinking about a DIY project in a future. Here's the problem, which motor is best for an electricar? Which have the best efficiency, torque and speed? Now considering that choosing an AC motor an inverter is needed and there would...

the velocity ratio of a machine is 5 and efficiency is 75%.what effort would be neede to lift a load of 150N with the machine?

i googled a lot, the best hit i got was " 'e' is a parameter which expresses the total variation of drag with lift. It is sometimes called the span efficiency factor or Oswald efficiency factor after Dr. W.B. Oswald who first used it. It would be 1.0 for an elliptically-loaded wing with no...

Hello all, I have probably a simple question for mechanical engineers. I would like to know the energy efficiency of real world freight elevators, going up with a speed of one meter per second. How about the best elevator's efficiency I could expect?

Homework Statement Exhaust gas expands through a nozzle whose isentropic efficiency is 88%. The inlet pressure and temperature are 1.6 bar and 400c respectively. At outlet the pressure has fallen to an ambient level of 1.013 bar. Given that the inlet velocity is negligible, and Cp and...

hey guys, I am new i didnt exactly which section to put this in...but i know it involves math so whatever ok i was on a paintball forum and this guy came up with a modification to do to a gun to increase air effiency (which is a very important aspect in a gun) In the firing chamber of...

Beta particle counting efficiency?? Hi! Can anyone tell me what counting efficiency means? For example if it's put into a question as: "shielded beta counter with 85.7% counting efficiency, 845 counts are accumulated in one week" what does it mean? How I understand it so far is that it's...