What is Efficiency: Definition and 945 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. F

    Air-Gap & Wireless Power Transmission Efficiency

    Summary:: How does the air-gap affect the efficiency ? For a wireless power transmission system, to what extend does the efficiency and coupling parameters get affected by the distance between the coils? What can be done to increase the power transmission or efficiency regardless of the value...
  2. M

    Increase efficiency in the cargo ship industry without a propellor

    Not sure if this is the right subforum to place this question? I stumbled on this idea, to make the cargo ship industry more efficient. The propellor of a cargo ship (<100m long) is relative inefficient, around 80% ( i know, this is pretty efficient for an boat propellor), and the harder the...
  3. person123

    I Computing the Speed of Traveling Waves in 2 Dimensions

    I have a 2-dimensionsal smooth function ##f(x,y,t)##. There may be multiple traveling waves across the domain. None of them are precisely traveling waves (the shape of the wave changes as it travels). Here is how one of these waves would look in 1-dimension: I want to find the speed of these...
  4. person123

    MATLAB More Efficient Way of Computing Neighbors in Range

    Hi. I have a collection of points in 3D space. I'm using MATLAB to find all pairs of points within a certain range from one another. Right now I'm using rangesearch(X,X,r), where X is the collection of points and r is the range. These points are the locations of atoms and I am attempting to...
  5. I

    Turboprop engine propeller efficiency data

    Hello, I'm looking for data on turboprop aircraft engine propeller efficiencies. I'm hoping for a table of available modern engines with a propeller efficiencies for comparison. I've tried Googling but not much luck. I can't even seem to find propeller efficiencies on the individual engine...
  6. XSummer32

    Efficiency of a heat engine given a P-V diagram of its process

    I post the working in the attached file
  7. K

    High-Pressure Turbine - efficiency

    Hi Guys, Why increasing the pressure ratio in a High-Pressure Turbine ( in a Gas Engine) , will increase the temperature of exhaust gas? Why is the amount of heat added per kg of the gas is higher? Is there any good material where I can read about this? Thank you in advance..
  8. S

    Steam boiler efficiency calculations

    Summary:: I'm going through my homework. I am confident I have everything correct except for my boiler efficiency. It seems too high at 99%. I would like to think my logic is sound but it can't be right. A boiler is designed to generate steam at 5 MPa and 400oC. A fuel is selected with a...
  9. phyzguy

    Efficiency of a heat engine in space

    I have a question about building efficient heat engines in outer space. In theory you could have a hot reservoir heated by the sun that was several hundred degrees C, and a cold reservoir that was very cold - maybe 50K - 100K or even colder. Thus, theoretically at least, a heat engine could be...
  10. S

    What is the efficiency of a Hobson's joint?

    A Hobson's joint is a kind of gearless angled drive. Most often a fixed 90 degree angle, but there is also versions with free moving joints in each axle so it can move to any angle up to a little over 90 degrees. It is today mostly just a novelty and there is very few applications actually...
  11. K

    I What is the difference between sensitivity and efficiency in particle detection?

    Hello! What is the difference between the sensitivity and the efficiency of a detector. In the detector books I found they seem to be treated as 2 different concepts, but based on the descriptions, I can't seem to understand the difference. Efficiency seems to be how many particles you detect...
  12. robotman

    Maximizing Efficiency: Solving Problems with Ease

    How to use efficiency in this problem?
  13. nomadreid

    I Ratio of a real value to the max theoretical value: what term to use?

    If the Summary is not clear, the following is an example translated from: https://telecombloger.ru/7335 '... air conditioning systems. For example, the efficiency of a compressor is about 85%. The remaining 15% is spent on friction, oil movement, overflows, heating, etc. The efficiency of the...
  14. greg_rack

    Efficiency of a hydroelectric power station

    I have found the input power through the efficiency formula, and I deducted that the input energy must derive only from water's kinetic energy... from which have mass/s and then finally the volume/s. After all the calculations and having multiplied the volume/s by 60, I get the result of 6.48 x...
  15. F

    Efficiency of charging new and old Li-ion batteries in electric cars

    An electric car has, say, a 50 kWhr battery. 1. How much electricity, in kWhr, is needed to add 1 kWhr of stored electricity to the battery? 2. After several years, the battery capacity has, say, fallen to 25 kWhr. How much electricity, in kWhr, is now needed to add 1 kWhr of stored...
  16. M

    Engineering DC Shunt Motor: calculation of the efficiency

    Hi, My main question is: should we be subtracting the rotational power losses from the motor output power in our efficiency calculation? My approach: Will skip extra work as I have done the above parts of the question correctly. I used power conservation to state that: $$ P_{input} = P_{motor}...
  17. Y

    Question about the efficiency of using an array or individual variables

    I have two questions here. In the program, I have two different boolean expressions, one using array A[10], the other just using individual variablesB(0..9). They both do the same thing as in the program. My question which one is faster in real life hardware? My guess is B(0..9) is faster even...
  18. L

    HVAC Efficiency of a homemade Air Conditioning unit

    Hi guys, I used to post on here quite a bit back in 2005-2007 when I was studying Physics in school, I remember it always being a great resource so hopefully I can get some similar help with this "real life" problem I'm having now! We are having a mini-heatwave here in the UK the last few...
  19. J

    Reversible Otto Cycle Efficiency: Investigating the Difference from Carnot's

    So we know that every reversible engine working between the same temperatures will have the same efficiency(the same as Carnot engine). So let's consider for example reversible Otto cycle. So as you can see on the picture it is operating between ##T_1## and ##T_3##, so I was thinking that it...
  20. B

    Engineering Velocity Ratio, mechanical advantage, Efficiency of a screw jack

    Hello, I have completed the question below. I am just unsure on whether i am correct or not. I am unsure on Mechanical Advantage. As i have seen a few different equations. Question: Answer: a) Velocity Ratio = $$\frac{\text{Distance Moved By Effort}}{\text{Distance Moved By Load}}$$...
  21. B

    Coupling Efficiency of LED to Fiber Optic Guide

    Most surface mount types of LED’s have a very nearly cosine distribution of light intensity. If we desire to inject light from an LED to the end of a cylindrical optical guide, what is the coupling efficiency as a function of distance (x) from the end of the guide? Assume that the LED is a...
  22. P

    Finding the efficiency of an ideal gas with adiabatic exponent 'γ'

    Here is what I did : work done in going from A to C, W1 = 2nRToln(2) (isothermal process) work done in going from C to B, W1 = pΔV = nRΔT = -nRTo (isobaric process) work done in going from B to A, W3 = 0 (isochoric process) so, total work done = W1 + W2 + W3...
  23. E

    Fiber coupling efficiency and general questions regarding ZEMAX

    Hello everyone, a friend and I are working on our master project at a university chair. The project is to set up a free space optics communication (FSO) to, eventually, transmit data. For this we want to couple our laser beam into a fiber at the receiving end, which is then plugged into our...
  24. U

    Efficiency and Energy to move a box on a conveyor belt

  25. M

    How to calculate the efficiency of a switch mode power supply?

    I know how to calculate the power output and input by analyzing the current in put and output with multimeters and using the formula P=VI. But P_out is obviously incomparably smaller than P_in so the efficiency would suck this way. Is there a better way to do this??
  26. WonderfulWorld

    Calculating the Efficiency, total output power and irradiance of LEDs

    Hi Everyone, This is my first post and I hope to work with you on this to gain a fuller understanding. I'm currently designing an LED circuit with 60 3 watt LEDs. Input power is both 120VAC for North American and 230VAC for other countries. I know this is pretty basicbut what is the best way...
  27. E

    Engineering Efficiency of Heat Engines & Refrigerators: Is Impossible Possible?

    For the heat engine: First I converted all the temperatures to Kelvin, ηmax=1-(333)/(1000)=0.667 ηclaim=(1*10^3)/(1.75*10^3)=0.5714 So the heat engine seems to be less efficient than a Carnot heat engine which means it can exist. For the refrigerator: COPmax=(253)/(363-253)=2.3...
  28. R

    Battery energy efficiency and Coulombic efficiency - what are they?

    I'm looking at two different batteries for home energy storage. Both batteries have a coulombic efficiency in the upper nineties, say 96%. One battery has an energy efficiency of 90%, and the other has an energy efficiency of 60%. I believe both ratings represent loses of usable energy, but I...
  29. B

    What is the efficiency of the circuit?

    The answer in the textbook's
  30. gregorspv

    The efficiency of a heat engine

    The first picture was provided along the problem statement. The second has my annotations. I initially began by calculating the ratio of efficiencies, since the work done is obviously the same and cancels out, but after failing and having seen the form of the solution I saw that that cannot...
  31. F

    Temperatures of the hot source and cold sink in a heat engine

    Hi, I was just wondering about the efficiency of a cycle that is not Carnot cycle. In that case one should use \eta = 1-\left|\frac{Q_{\rm out}}{Q_{\rm in}}\right|, where Q_{\rm in} and Q_{\rm out} are the amounts of heat absorbed and released during the cycle. For instance, I guess that in...
  32. RyanRhino

    Calculate the average force used to drag a box up a ramp

    I first wrote down that 55% = Eout/Ein I also know that W = (Facos20)(4) and I substitute it into the first equation 55% = Eout/[(Facos20)(4)] But I'm missing two variables here. Did i forget something or is the question missing some information?
  33. E

    Breeder fuel efficiency question

    I've looked reasonably to see if I could find this answer, I'm not a nuke engineer so perhaps my search terms are not correct. I've seen the fuel cycle charts (eg:https://en.wikipedia.org/wiki/Thorium_fuel_cycle, but not clear how to work from this to a percentage mass consumed) I'm interested...
  34. Stephen Bulking

    Thermodynamics problem involving engine efficiency

    Q2: An engine has power of 26.5 kW, needs 9 kg coal during an hour for energy. The heat capacity of coal is 7800 cal/g. Define the engine’s efficiency. Qh= mcΔT = 9000x7800xΔT ( stuck) P=26.5kW(is this the power output of the engine in an hour?) If only I could find ΔT, thenI would be able to...
  35. K

    Efficiency of heating up aluminum vs steel by induction

    Summary: In a heating by induction experiment performed, the idea was to determine the efficiency of heating up a small steel cylinder, an aluminum cylinder and then compare the two efficiencies. The cylinder was surrounded by a metall coil that alternating current was going through...
  36. fight_club_alum

    Inductor Efficiency: Does it Produce More Current?

    Hey everyone, I am taking a circuit 1 course in college and was wondering if an inductor is actually efficient. What I mean is that does it produce more current than the current already supplied. I know it keeps the circuit going even after the voltage source is cut, but does that mean that, if...
  37. Alfreds9

    Saw characteristics influencing efficiency in sawing steel?

    Hello, I am having a headache to try understand a possibly simple real-world problem: efficiency (as in number of strokes/cumulative length needed) to saw steel, assuming a constant sawing length per stroke and a known steel sectional area. I began to think about the few assumptions I assume...
  38. J

    I Neutrons, fusion and efficiency

    Regarding electricity generation from a fusion reactor: I can't seem to find any discussion about the percentage of fusion product neutrons that can be realistically caught in the thermal blanket to utilise the energy they carry from the fusion reaction. The neutrons from fusion have to be...
  39. O

    I Efficiency of computers vs. brains

    Hi, I’m an undergraduate student interested in cognitive processes. I’m about to ask a very interdisciplinary question, and so hopefully I can find a physicists that can take on the challenge. What is the fundamental reason behind why modern electronic computers (transistor computers) are...
  40. A

    What is the most efficient method for heating plasma in fusion reactors?

    Hi, of all the main plasma heating techniques employed by multiple fusion reactor designs, namely 1) ohmic heating 2)RF 3)neutral beam 4)some other method? Which of them is the most efficient in terms of how much of the input electricity gets converted to direct heat/kinetic energy of the...
  41. L

    Thermodynamic Systems - Power rating and thermal efficiency

    A coal fired steam plant takes in feed water at a temperature of 70°C and produces 15 tonnes of steam per hour at a pressure of 60 bar and temperature 400°C. The fuel consumption rate is 1.5 tonnes per hour and the calorific value of the fuel is 40MJkgˉ¹. Determine the power rating of the boiler...
  42. N

    Engineering Calculating Efficiency and Speed of a DC Motor at Half-Load Torque

    First some basic figures which are very rounded as I'm interested in the approach to the problem rather than accuracy of the answer at this stage: The field current will be 500/220 = 2.2727 Amps, and so power is a fixed loss at 1136.36 Watts The armature current is 45 - 2.2727 = 42.72 Amps. At...
  43. Q

    Solar cell absorption efficiency in COMSOL Multiphysics

    Hi. I am studying the effect of plasmonic nanoparticles on solar cells. Is there a way to calculate absorption efficiency in different layers of tandem solar cells in COMSOL Multiphysics.
  44. didaw

    The efficiency of a furnace’s heat transfer process

    If I am honest with you I don't even know where to start, if someone wouldn't mind helping me find a starting point? Additional information Melting point of aluminium 660°C Specific heat capacity for aluminium (cp): 0.91 kJ/kgK...
  45. L

    What is the difference between lumen efficiency and efficacy in lighting?

    [Moderator: Moved from a homework forum. This question is not like most homework.] Problem Statement: I have been lighting and on lumen efficiency and efficacy. I have got bit confused between them Im looking at metal halide and fluorescent. when googling efficiency and efficacy for both. It...
  46. H

    I How do you exactly calculate the theoretical maximum efficiency of an LED?

    Hi! I found interesting post here: https://electronics.stackexchange.com/questions/325762/how-efficient-are-leds However, it only gives the final results and not the steps he made. I tried to learn the formulas on wikipedia on my own but I couldn't figure out what variables need to have what...
  47. Charles Bagwell

    How can I calculate the efficiency of my microwave oven for steam production?

    I am working at retrofitting a microwave oven to produce steam for my 3 HP steam engine/generator. I have read estimates of 50-70% efficiency, but I am trying to verify those figures. Can anyone point me in the direction of calculating the efficiency myself?
  48. TheBigDig

    Efficiency of the Rankine Cycle

    WT, the work done by the turbines, as the difference in enthalpy from point 2 to point 3 WP, the work done by the pumps as the difference in enthalpy from point 4 to point 5 Q as the difference in enthalpy from point 3 to point 4 Taking these I get h5 = -252.3kJ/kg. However, my work ratio is...
  49. TheBigDig

    Efficiency of a steam power plant

    My inital assumption was to just take T1 = 5600 and T2= 300K, find the maximum efficiency and then divide it by two and three but I don't believe this question to be that simple. I'm confused as to where the 750K fits in as I thought no matter what occurred in between the heat reservoir and heat...
  50. T

    Efficiency of a Heat Engine: How to Calculate Heat Transfer in a Monotonic Gas

    Homework Statement I am having an issue trying to decipher this question, as I am not sure if it a lack of knowledge on my half or there is an assumption I have to make. Homework Equations ##\epsilon=\frac{W_{total}}{Q_{in}}## The Attempt at a Solution My issue is calculating the heat...
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