What is Efficiency: Definition and 947 Discussions

Efficiency is the (often measurable) ability to avoid wasting materials, energy, efforts, money, and time in doing something or in producing a desired result. In a more general sense, it is the ability to do things well, successfully, and without waste. "Efficiency is thus not a goal in itself. It is not something we want for its own sake, but rather because it helps us attain more of the things we value". In more mathematical or scientific terms, signifies the level of performance that uses the least amount of inputs to achieve the highest amount of output. It often specifically comprises the capability of a specific application of effort to produce a specific outcome with a minimum amount or quantity of waste, expense, or unnecessary effort. Efficiency refers to very different inputs and outputs in different fields and industries.

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  1. G

    Why is 100% efficiency impossible for heat engines?

    My question involves heat engines. I understand that a heat engine typically uses energy provided in the form of heat to do work. According to the 2nd law of thermodynamics, however, not all heat energy can be converted into work energy, meaning that heat engines are not perfect. At least some...
  2. P

    Carnot cycle with efficiency > 1

    Is it possible (at least theoretically) to construct engine which uses Carnot cycle and two reservoirs with temperatures T_1<0<T_2 (one of them has negative temperature which is possible e.g. in case of two-state paramagnet). Such cycle would have efficiency greater then 1. (of course the...
  3. DARKSYDE

    Boosting Your Fuel Efficiency When You Reach C: The Impact of Mass Increase

    when approaching C the mass of your craft increases. If the mass of your fuel increases also wouldn't that mean the faster you go the more fuel youll have?
  4. R

    Improving Fire Tube Boiler Combustion Efficiency: What Software Can I Use?

    currently, I'm be studying on improving fire tube boiler's combustion efficiency. so, i need a software which is applicable to the title above in order to prove my calculation according to the formula. can u tell me what software can be used?
  5. V

    Understanding Efficiency Calculations

    Hello, I just saw something that is a bit confusing to me and i hope someone could explain the difference. I read something about an energy production system design and there are some calculations including some losses of the system. Taking into account the inverter losses, let's say for...
  6. I

    Turning MPG into % efficiency?

    This seems pretty hard to do but is there a way to figure out how efficient a vehicle is based on fuel used and MPG? I know there's about 1/3 gone to exhaust 1/3 through radiator and 1/3 is work but I want to get an exact percentage on the work part. So it would be 33% if it was like what I...
  7. F

    New 4 stroke engine efficiency

    The new issue of the mechanical efficiency of the new 4 stroke engine.What will have the efficiency of the engine, which increases its volume swept by two times slower rotating crankshaft- piston systems ?? Two times slower or inertia four times smaller. Regards Andrew
  8. D

    Efficiency of a cycle in TS diagram

    Homework Statement A working substance goes through a cycle within which the absolute temperature varies n-fold, and the shape of the cycle is , where T is the absolute temperature, and S the entropy. Find the efficiency cycle. Homework Equations \frac{\delta Q_R}{T}=dS...
  9. Z

    Transformer efficiency conversion

    Greetings physics gurus Im getting bogged down on conversion of the VA to A Homework Statement A small transformer used to power a laptop computer has the following characteristics printed on it: • input AC 220 V, 50 Hz, 15 VA. • output DC 5.0 V, 1.0 A. Is this transformer...
  10. B

    Bicycle gear ratios for maximum efficiency

    We all know that there are several options of front sprocket/rear sprocket combinations that achieve the same gear ratio. i.e. A large front sprocket with medium rear or medium front with larger rear will produce the exact cadence at a given speed. What I've always wondered, is there any...
  11. K

    Why Does Low Level, High Speed Flight Decrease Aircraft Efficiency?

    hey, I was reading Aircraft Design: A Conceptual Approach by Raymer and i came across the following line. ' The aerodynamic efficiency of an aircraft, expressed as the lift to drag ratio is greatly reduced during low level, high speed flight as well is its engine efficiency. ' Can someone...
  12. C

    How Efficient Are Linear Generators Compared to Radial Generators?

    I have been having difficulty finding information regarding Linear Generators, maybe they have not been used enough and are begininning to be sought after more for renewable energy production. Back to the title, does anyone know approximately the efficiency of a linear generator, or at...
  13. C

    Air Conditioner Efficiency - Humidity & Precooling

    I have two questions/ideas about the efficiency of A/C's that I'd like to bounce off you guys. I couldn't find anything on Google about either of these items being discussed before. 1) Precooling The first thought I was wondering was whether it was more efficient to pre-cool your house in...
  14. S

    Fuel Cell Efficiency: Average Output for Cars, Homes, & More

    I understand that generating the hydrogen that powers a typical fuel cell is (prohibitively?) energy intensive at this point, but I was curious about the following: Assuming a sufficiently efficient catalyst was obtained that allowed large-scale production of pure hydrogen without...
  15. M

    Transformer Efficiency Calculations

    Hey. I am currently doing a bit of revision for an exam and I am struggling on the following question: I understand the whole voltage/current/power/impedance ratio stuff, but can't seem to find any information on calculating efficiencies using the resistances or the transformer core losses...
  16. J

    Estimating efficiency of sum frequency generation

    I want to estimate the efficiency of SFG in a BBO crystal for the situation when one pulse has much higher energy than the other (nJ compared to fJ), and the beams cross at an angle in the crystal. Can anyone recommend a resource that would help with this?
  17. L

    Energy efficiency of torsion Catapult

    Homework Statement How would you find the energy efficiency of a torsion catapult ? (one i built for project) I have the Force at which I am pulling the arm. F = 20N also the angle from origin to the point of release ( or when the ball leaves the arm) Theta = 50 degrees...
  18. P

    Efficiency of an inclined plane

    Homework Statement List 2 major factors result in an efficiency of less than 100% when using an inclined plane to raise a mass Note - this is a grade 11 lab so don't have answers that are too advanced please :DHomework Equations eff = eout/ein x 100% ... = mghf/fd x 100%The Attempt at a...
  19. Y

    Efficiency of Power Line Transmission

    Homework Statement Homework Equations N/A The Attempt at a Solution I have been struggling with these questions for the past week, with not much result at all. I have to study at home, through the use of various textbooks, and with no teacher to guide me through the process...
  20. C

    Efficiency of Ramp Pulling: Friction vs. No Friction

    Homework Statement In an ideal case of pulling a cart up a ramp where there is no friction should the efficiency be less than that of pulling a cart up a ramp with friction?Homework Equations W=F\DeltaXcos\theta Efficiency=(work output/work input)*100 The Attempt at a Solution I was trying to...
  21. J

    Thermal Efficiency of a power plant

    Homework Statement The electric output of a power plant is 750 MW. Cooling water flows through the power plant at the rate 1.0*10^8 L/hr. The cooling water enters the plant at 16 degrees C and exits at 27 degrees C. What is the poer plant's thermal efficiency? Homework Equations W =...
  22. S

    Does Revving Closer to Peak Power Improve Fuel Efficiency in Motorcycles?

    When I got my motorbike it had a non-standard rear sprocket with two extra teeth. I decided to swap it for a standard one. I expected to get a better overall mpg, but it didn't change noticeably. So... An engine has a red line at 14000 rpm. Peak power is delivered at 12000 rpm. Driving...
  23. J

    Q: Can Matter Be Converted to Energy with 100% Efficiency?

    Hi everyone, Somewhere I've heard of a special type of laser which when it strikes matter could convert near 100% of it into energy, the laser's energy being insigificantly small as compared to the output thus achieving ~100% efficiency? Is this a way or is there any other means to achieve...
  24. K

    How Efficient Is a Steam-Electric Power Plant That Delivers 900 MW?

    Homework Statement (c13p30) A steam-electric power plant delivers 900 MW of electric power. The surplus heat is exhausted into a river with a flow of 6.29×10^5 kg/s, causing a change in temperature of 1.03 oC. What is the efficiency of the power plant (in % Don't enter a unit.)? Homework...
  25. S

    Calculating Thermal Efficiency for a 4-Process Cycle

    Homework Statement i have an mechanical engineering problem. A gas taken thru a 4-process cycle has 1-2 isothermal volume ratio rv,2-3 isobaric constant pressure,3-4 isentropic reversable adiabatic and 4-1 isochocric constant volume. How do i formulate the thermal efficiency equation for it...
  26. P

    How Should the Spring Constant k Affect the Efficiency of a Catapult?

    Independent variable and spring constant k Hi all, If someone could spare a minute to help answer my question I would appreciate it greatly, I am trying to design an experiment to investigate the efficiency of a catapult, But need help in what i should use as the independent variable-...
  27. 3

    Propeller Efficiency Report: What to Include & Refs

    i will make an report about the propeller efficiency can anyone help me and tell me the things i need to put in this report and the references i can use
  28. P

    Help in calculating efficiency of a catapult

    Help with a catapult Homework Statement Hi all I have design a prac to investigate the efficiency of a catapult, was wondering if anyone could shed some light into this area Homework Equations Ee=0.5kx^2 (hookes law) The Attempt at a Solution I was thinking that my independent...
  29. M

    Can Propeller Efficiency be Calculated from Scratch?

    Now i am doing study on vessels propeller efficiency which i can determine the best time to do propeller polishing.Do anyone have any idea on how do i calculate this propeller efficiency
  30. T

    Efficiency vs Height: Understanding the Relationship

    Homework Statement Hey guys! I am doing a very simple lab, and in need of your expertise! Haha, I am an intro-physics student, please don't get too complicated with me, my knowledge is very limited. The QUESTION is: WHAT IS THE RELATIONSHIP BETWEEN EFFICIENCY VS HEIGHT...
  31. FeDeX_LaTeX

    Can We Achieve 100% Efficiency? Renewable Components Explored

    Hello; Is there a 100% efficient component? One where there is no waste energy? Or something that is completely renewable such that all the energy wasted is put back into the component?
  32. D

    Carnot efficiency: is heat always positive?

    This is a very quick question but in the equation e=1-Q_{C}/Q_{H} do we treat both Q's as positive even though heat goes in in one case and out in the other? Or is there some detail I'm missing that would otherwise make the result less than 1.
  33. G

    Quantum efficiency as a function of wavelength

    I'm trying to reproduce the plot in the attached figure. I know the band-gap energies, so I was hoping there was some simple way I could get the quantum efficiency as a function of wavelength. I read on wiki that Energy(eV) = 1240/wavelength(nm), so I mechanically plugged those in, and got...
  34. B

    Electric Motor Efficiency: Maths Homework Answers

    Homework Statement A Student Performs an experiment in which an electric motor is used to lift a 200g weight through 2m, thus increasing its potential energy by 4j. From measurements of the rate at which the weight is lifted the efficiency of the motor is to be determined. Two different...
  35. E

    The theoretical maximum efficiency of silicon solar cells is about 29%. Why?

    The theoretical maximum efficiency of silicon solar cells is about 29%. How is this theoretical maximum efficiency derived? How can I use the working principles of a silicon solar cell to explain this?
  36. C

    Optimizing Compressor Efficiency: Small vs. Large Volume Gas Compression?

    for a given volume of gas,is it more efficient to compress smaller volumes of gas more no. of times or compress large volumes of gas less no. of times?
  37. P

    Max efficiency (thermodynamics)

    I'm observing the circular process of a heat engine. It's p-v diagram is So between points 3 and 4 the heat is extracted. That causes losses since the efficiency if given by \eta =1- \frac {Q_c} {Q_h} Where Qh is the heat the heat source has given and Q_c the amount of heat that...
  38. B

    Calculating the Efficiency of a Transformer for a Small Appliance

    Homework Statement The specifications of a transformer for a small appliance read "Input: 110 V, 6.4 W" and "Output: 8.9 V, 270 mA". What is the efficiency of this transformer? Homework Equations P = I * V V = I * R The Attempt at a Solution 6.4 W / (8.9*(270*.001)) ---> I think this is...
  39. C

    What is the Efficiency of a Carnot Engine?

    Homework Statement http://img291.imageshack.us/img291/7786/effx.jpg Homework Equations e=1-1/(V1/V2)^(gamma-1) The Attempt at a Solution This is a practice test where he gives the solutions, as you can see the first thing he asks for is the efficiency, and lists the answer as...
  40. B

    Efficiency of latest photovoltaic panels

    What is the efficiency of the latest photovoltaic panels and also wind turbines? I read in an article that the highest efficiency reached by photovoltaic panels was around 40%, which seems to be very very high.
  41. A

    Efficiency of Ejector as pump

    Efficiency of Ejector "as pump" I was asked to find the efficiency of a steam ejector experiment "as a pump". So I tried the formula : [(m(P/density + V^2/2))discharge - (m(P/density + V^2/2))suction]/ (m(P/density + V^2/2))steam inlet. I am getting an efficiency of 0.5%. Is this a...
  42. Q

    Gamma ray spectroscopy: Germanium detector efficiency calibration.

    Hi all, Got a bit of a problem with a lab experiment at uni (I'm not sure if this is the right place to post this, mods feel free to move it if necessary!) Anyway: We're trying to get a plot of efficiency against energy for a planar germanium detector. We've got spectra for different...
  43. S

    Battery efficiency and internal energy

    Homework Statement One rechargeable battery of mass 15.0 g delivers to a CD player an average current of 15.5 mA at 1.00 V for 2.50 hr before the battery needs to be recharged. The recharger maintains a potential difference of 2.00 V across the battery and delivers a charging current of 10.0...
  44. Wellesley

    Thermodynamics - Carnot efficiency

    Homework Statement On a hot day a house is kept cool by an air conditioner. The outside temperature is 32°C and the inside temperature is 21°C. Heat leaks into the house at the rate of 9000 kcal/h. If the air conditioner has the efficiency of a Carnot engine, what is the mechanical power that...
  45. K

    Efficiency in trebuchet design

    The medieval trebuchet is a missile-throwing device, with a heavy counterweight on the short end of a beam that pivots about an axle fixed to a supporting frame. A sling is attached to the long end, and when properly "tuned" by adjusting its length, it will release the missile at exactly the...
  46. B

    Cap input filter rectification efficiency

    A question regarding power supply efficiency: The theoretical maximum efficiency of a full-wave rectifier circuit with a resistive load and no smoothing is around 82%. In the calculations to derive that the resistance of the source or the rectifiers does not enter into the equation, so the...
  47. kjohnson

    Programming Efficiency N-body problem

    I am currently in the process of writing a program in VBA that will numerically "solve" a given n-body gravitational problem. I'm doing this pretty much just for fun and am by no means a programmer (had a 1 semester course in c++). The question I have is something that seems to keep coming into...
  48. D

    Does a Higher K Value in a Spring Lead to More Efficient Energy Transformation?

    Homework Statement Well, this isn't really a number question, but I'm wondering if the larger the k of a spring, if that will make the energy transformation of a weight from potential energy to spring energy more efficient? Homework Equations F=-kx ; energy before = energy after The...
  49. M

    Find Optimal Speed for Fuel Efficiency in a Car

    Hi, I would like help to solve the following question. Q: The graph shows the fuel consumption c of a car (measured in gallons per hour) as a function of the speed v of the car. At very low speeds the engine runs inefficiently, so initially c decreases as the speed increases. but at high...
  50. P

    How Can Efficiency Be Maximized in a Velocity Compounded Impulse Steam Turbine?

    hii frends, im a doing a project on the efficiency improvement of a velocity compounded impulse steam turbine. we plan 2 do that by varying the input mass flow rate of steam and finding out the particular mass flow rate at which maximum efficiency is attained. the data i could collect...
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