Efficiency Definition and 948 Threads

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. T

    Digestion-carbohydrate-ATP-energy efficiency

    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...
  2. F

    Thermodynamics - efficiency of power plant

    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...
  3. V

    How Can Isentropic Efficiency Be 90% If Entropy Remains Constant?

    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...
  4. T

    Calculating Efficiency of Solar Panel with Light Bulb

    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...
  5. M

    Increase the efficiency of brakes in an ATV?

    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...
  6. L

    Thermal Efficiency of an air conditioner

    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...
  7. C

    Thermal efficiency of a coal powered power station

    [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...
  8. U

    Electromagnetic Radiation Propagation and Efficiency

    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...
  9. E

    What is the typical efficiency of a muon detector at an accelerator experiment?

    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...
  10. P

    Medical Super Humans: Exploring the Potential of 100% Energy Efficiency

    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?
  11. C

    Thorium vs Uranium: Examining Heat Transfer Efficiency

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

    What is the true statement about Carnot engine efficiency?

    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...
  13. F

    How Does the Efficiency of an Ideal Gas Engine Change Through a Four-Step Cycle?

    Homework Statement An engine using 1.00 mol of an ideal gas initially at a volume of 24.6 L and a temperature of 400 K performs a cycle consisting of four steps: (1) an isothermal expansion at a temperature of 400 K to twice its initial volume, (2) cooling at constant volume to a temperature...
  14. J

    What is the efficiency of a solar collector made of an aluminium canister?

    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...
  15. E

    Calculating Thermal Efficiency of a 4-Process Heat Engine: Otto or Diesel Cycle

    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...
  16. S

    Comparing Efficiency of Solar Energy Trapping Methods

    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...
  17. B

    Efficiency of RWD vs. AWD at high speed

    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...
  18. W

    Questioning the Efficiency of a Heating/Cooling System as a Heat Engine

    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...
  19. U

    Efficiency of a modern internal combustion engine

    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...
  20. P

    Efficiency of Siphons: Vacuum & Pressure

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

    How Can I Maximize Efficiency in a 1 Joule Vehicle Project?

    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...
  22. Z

    How Much Exhaust Heat Does a Nuclear Power Plant Discharge Per Hour?

    [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...
  23. D

    What does the efficiency bell curve of a good power supply look like?

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

    What is the efficiency of the engines?

    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 =...
  25. M

    Step down transformers & 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
  26. L

    Maximum efficiency = Carnot cycle

    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?
  27. W

    Compare the efficiency of two cars.

    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...
  28. D

    Thermodynamics energy efficiency

    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...
  29. K

    What Is the Source Voltage and Additional Resistance for Power Efficiency?

    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...
  30. G

    Percent efficiency of three power generators

    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...
  31. R

    Efficiency of a hydrogen fuel cell

    I'm trying to calulate the efficency of a small hydrogen fuell cell that I built. I have all of the measurements, but I'm not coming up with a resonable effiency. The power to electrolyze the water is the P IN. 3.25 W =2.5 V x 1.3Amps (.21 mA) We measured the electrical power out...
  32. I

    Solving Energy & Efficiency Problems with PV Conversion in US

    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...
  33. Loren Booda

    Where to best increase efficiency?

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

    Increasing efficiency of PV cell

    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...
  35. D

    How Does Distribution Coefficient Affect Solvent Extraction Efficiency?

    Extraction efficiency problem PLease help... Homework Statement 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 mL of water by a single...
  36. L

    How can i find the efficiency of a trebuchet and/or catapult

    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...
  37. M

    Power Plant Efficiency & Heat Dissipation Calculations

    [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...
  38. M

    Understanding Wattage and Efficiency in Electrical Appliances: Explained

    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...
  39. L

    Best efficiency DC or AC motors?

    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...
  40. P

    Machine efficiency velocity ratio

    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?
  41. A

    Maximizing Aircraft Performance: Understanding Oswald Efficiency Factor

    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...
  42. L

    How Efficient Are Freight Elevators and Can They Regenerate Electricity?

    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?
  43. N

    Thermo Q RE:isentropic efficiency through nozzles

    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...
  44. H

    Math Modification to Increase Air Efficiency in a Paintball Gun

    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...
  45. W

    Beta particle counting efficiency?

    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...
  46. K

    Trying to make a cantilever with the highest efficiency

    Right now I'm trying to make a cantilever with the highest efficiency. I'm trying to design several models but I have questions: How can one make one without having to find the best design through numerous times of trail and error? Is there an equation for cantilevers which dictate the...
  47. L

    MCNP4C: efficiency calculation

    Any one familiar with MCNP4C efficiency calculation can help me with this? My cal. result for 1.836MeV(e.g.) is always small (6.16447E-05 ) compared to it should be(3.78E-004 by a professional business software), here is the inp file, is there anything wrong with the geometry define or source...
  48. S

    Figuring out the efficiency of an inclined plane

    Homework Statement Rather than lifting a 225kg motorcycle 60cm on a truck, Samantha uses a 4m plank as an incline and only requires 345N to push up the ramp Homework Equations The Attempt at a Solution To find work output, i did .6M X 2250N giving me 1350 J To find work...
  49. X

    Efficiency of a Cart Rolling Down an Inclined Plane

    Homework Statement Alright for this thing, we had to pull a cart up a inclined plane and time how long it took to get to the bottom. Distance from ground to top of inclined plane is - 0.125m Length of Board is - 1.21m Mass of cart - 1.09kg Force to pull cart up - 1.4N Time it took for...
  50. A

    Efficiency of Two Carnot Engines in Series

    Homework Statement There are two Carnot engines in series, so that the heat exhaust from the first engine drives the second. Find the overall efficiency of the arrangement which contains only the efficiences of the individual engines. Homework Equations \epsilon = \frac{W}{Q_{input}}...
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