Efficiency Definition and 950 Threads

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...

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...

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...

Homework Statement What could you do to increase efficiency between the cart and the ramp? As in pulling a cart (with wheels) up an inclined plane. Homework Equations The Attempt at a Solution One solution could be increasing the angle to increase efficiency. I was wondering...

Does a 60W Type A (general service) incandescent light bulb put out more light than a 60W Type B (candelabra torpedo) incandescent light bulb?

So I did a lab experiment and found out that the higher the angle, the more efficient the ramp is, and just curious, does anyone know the reason for this? Any info provided would be greatly appreciated.

Greetings Engineers & Scientists. This is my first post. I'm an accountant so excuse my ignorance. See diagram attached. I want to calculate how much volume expansion there would be if we vapourised n-pentane. I did this experiment with air (on a smaller scale) but there was not much...

As the solar cell gets further away from the light source, does it get more efficient or less efficient? At the moment I am able to work out how much power enters the solar cell. However, it is pretty weird because as I found out from my experiment, the efficiency of the solar cell gets better...

definition wise i got the difference between these two efficiencies. but in practice how does these two differ? i was referring to this book: Jet propulsion: a simple guide to the aerodynamics and thermodynamic design ... By N. A. Cumpsty he has mentioned this: "using polytropic...

Homework Statement A heat engine operating between 78.5oC and 204oC achieves 20.6% of the maximum possible efficiency. What energy input will enable the engine to perform 10.2 kJ of work? The only help I need with this is exactly what equation(s) to use. I would think thermal efficiency...

I've just completed a lab session on the Rankine Cycle using R141b as the working fluid and have obtained some values for the different effciencies in the cycle. I have that; ηTheoretical =13.01% ηPractical =12.07% ηIsentropic =5.90% I'm pretty sure I've followed the lab sheet correctly...

I understand that all real-world applications can never attain 100% efficiency, whether it be referring to something mechanical, electrical, or some thermodynamic cycle. While studying the Carnot cycle and learning about the upper limit of efficiency for thermodynamic cycles, I drew a blank...

Homework Statement Derive the efficiency for production of a particle of rest mass m made by colliding a 'bullet' particle of mass M with a stationary target particle mass N. Homework Equations ans is k^-1 =1 + (m+2M)/2N The Attempt at a Solution \bf{P_1} + \bf{P_2} =...

Homework Statement An 8.5 X 10^3 kg elevator is pulled up at a constant velocity of 1m/s by a 10kW electric motor. Calculate the efficiency of the electric motor. Homework Equations P=w/t %efficiency=work out/work in X 100% W=mgh d=vit+1/2at^2 v=d/t The Attempt at a Solution The...

Homework Statement A engine used to raise a lift is 60% efficient, and the lift's mass is 2000kg. How much energy would be needed to raise it to 10m?Homework Equations Efficiency = energy output/ energy input *100 The Attempt at a Solution EP=mgh = 2000*9.8*10= 196000 J. Therefore, eff...

Suppose an engine uses multiple heat reservoirs: When calculating the carnot (maximum possible efficiency) is it valid to simply take the average of the temperatures of the hot reservoirs from which the heat is extracted as T(hot) and the average of the temperatures of the heat sinks to which...

Homework Statement This is from "Equilibrium Statistical Physics" by Plischke and Bergerson, problem 1.1: "Consider a Carnot engine working between reservoirs at temperatures T1 and T2. The working substance is an ideal gas obeying the equation of state [ PV=Nk_BT ], which may be taken to be...

Homework Statement A washing machine that weighs 1400N must be put into a delivery truck bed that is 1.2 m off the ground. A worker uses a force of 450N to push the machine up a ramp that is 4.3m long. What is the efficiency of the inclined plane?Homework Equations e=(MA/IMA)100---- efficiency...

I've been trying to understand why fuel economy decreases when the engine gets into higher RPMs. That is, if you put the pedal to the metal and quickly accelerate to 40 MPH, your engine operates much less efficiently than if you slowly accelerated to 40 MPH. Here's where it seems the...

How calculate propeller efficiency if I know propeller trust ant motor power and motor efficienty?

I'm not using the template because this is a rather abstract question about the way to approach a scientific experiment. I'm beginning a science project in which I hope to define the speeds at which using an air conditioning unit becomes more efficient than rolling the windows down in a car...

Homework Statement A power cycle has a thermal efficiency of 40% and generates electricity at a rate of 100 MW. The electricity is valued at $0.08 per kW * h. Based on the cost of fuel, the cost to supply Qin is $4.50 per GJ. For 8000 hours of operation annually, determine, in $. a. The...

Homework Statement The efficiency of electron excitement by photons is described as being related to how much different orbitals share the same k-space or momentum space. Is this similar to orbital shape (eg spheres, dumbells, ec)? Homework Equations The Attempt at a Solution I...

Homework Statement A photovoltaic cell has area 80 sq cm and efficiency converting energy in the form of sunlight to electricity of 7%. The sun's intensity is 800 W / sq m and the rays are perpendicular to the cell's surface. What power will be produced by this cell (in W)? Take care in...

Homework Statement An electrical power plant manages to transfer 88 percent of the heat produced in the burning of fossil fuel to convert water to steam. Of the heat carried by the steam, 40 percent is converted to the mechanical energy of the spinning turbine. Which best describes the...

the carnot engine does not obey any law of thermodynamics,because it has 100% efficiency,now do we have any engine that has come close to this hypothetical engine?(in terms of efficiency ) can this process of carnot be used for a 6 stroke engine?(hypothetically)

Hey, I was wondering if someone could link me to a good source where I can read about electrical generator efficiencies and how they relate to RPM. I tried doing some derivations myself and came up with a somewhat believable result, but am not ready to trust myself as this is far outside my area...

Could a 10 HP diesel engine be made as fuel efficient as say a 100 HP diesel engine, that is (work done/fuel used). Does thermodynamics prevent a smaller engine from being more efficient? Thank you for your time.

It seems to me a typical gasoline car has wastes about 95% of the gasoline energy before any rotating energy gets to the wheels. Here's my reasoning. I once measured my cars efficiency (an old Renault 5). I drove 100 km/h (28m/s) on a flat and level freeway, with no wind, and set the gears...

Homework Statement Neon gas at the rate of 100kg/min enters an adiabatic turbine at a temperature and pressure of 1073K and 1.5 MPa. The gas leaves the turbine at a pressure of 200kPa. If the real(actual) power output of the turbine is 370 kW, determine the isentropic efficiency of the...

Hi, I've been attempting this problem all week now and I can't seem to even begin to obtain an answer which is highly frustrating, so here's the problem: An electric boiler is required to raise the temperature of 90 litres of water per hour by 35oC. If the input required to affect this...

quick question, is the difference between a carnot engine to an engine is that the engines eff is less than or equal 1-(cold temp / hot temp), and the carnot is the max of this which is just equal 1-(cold temp / hot temp)?

In order to build a QE measurement system, I want to confirm the following issues: (1) Is collimated light required for QE characterization of the entire solar cell? How "bad" it could be if having Gaussian beam? (2) It seems LBIC is most common for QE mapping. Is it possible to use...

Like the title states, is the voltage produced by a photodiode, or any PV device for that matter, dependent upon that devices temperature? To rephrase, if you have a fixed amount of photons coming in contact with the business end of a photodiode, is the voltage or current generated by the...

Hello - I'm having some problems understanding Gibbs energy of formation, and how it's applied to electrolysis. So, I'm hoping someone can explain what I'm doing wrong.. According to his site: http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/electrol.html (image) The change in the Gibbs...

Homework Statement Derive an expression for the effiency of the cycle (of a Stirling Engine) working between two heat baths at temperatures T1 and T2 with volumes in the ratio V2/V1. Assume the working substance is a monatomic ideal gas. Homework Equations Work done=heat absorbed from...

Hi, How do I calculate the fan power (kW) and efficiency, given the flow rate, static/total pressure across the fan surface? Do I need more data? Thnx in advance.

I had to do an experiment in which I built examples of hexagonal closest packing, face-centered closest packing and a body-centered space lattice. I had to find the volume of a box that would fit tightly around them, and then calculate the density in units/cm3 (assuming a mass of 1 unit per...

Homework Statement So, I have a 5.0 kg rat that goes down a ski slope, slides along a rough patch, and then smashes into a vertical board with a spring attached. I need to find out the efficiency of the spring with this information: m=5.0 kg v (after sliding across rough patch)=108 m/s ; it...

Homework Statement What is the the efficiency of a transformer with 13w of primary power. 120Vp, Np unknow 12Vs, 90Np Homework Equations The Attempt at a Solution eff= Psec/ Pri * 100

Homework Statement 1. Homework Statement A power plant taps steam superheated by geothermal energy to 505 K (the temperature of the hot reservoir) and uses the steam to do the work in turning the turbine of an electric generator. The steam is then converted back into water in a condenser...

Homework Statement A power plant taps steam superheated by geothermal energy to 505 K (the temperature of the hot reservoir) and uses the steam to do the work in turning the turbine of an electric generator. The steam is then converted back into water in a condenser at 323 K (the temperature...

Homework Statement The question asks us to advise the company on a heat pump (and give reasons) which is claimed to deliver 1500J to a room at 280K by consuming 50J of work per cycle pumping heat from the surroundings at 270K. I've drawn a diagram of the heat pump, taking heat Q2 from a bath...

Hello again, all! I have another basic thermodynamics question :P This one came from a 2008 admission test. Seems simple enough, but as usual, my answer doesn't match =P Homework Statement A monoatomic ideal gas performs, reversibly, the cycle shown in the diagram attached in this post...

Homework Statement A heat engine operates between a reservoir at 25 degrees Celsius and one at 375 degrees Celsius. What is the maximum efficiency possible for this engine? Homework Equations e = \frac{Qc}{Qh} The Attempt at a Solution I'm afraid that the equation above...

process A: isothermal compression at low temperature with an input of work of 83 J process B: constant volume increase in pressure with an energy input by heating of 200 J process C: isothermal expansion at high temperature with work output of 139 J process D: constant volume cooling to the...

I wonder what's the best efficiency that's possible to achieve with a continously variable transmission. I've googled a lot and can't find anything useful (with useful i mean an approximate value in [%]). thanks.

I learn that increase of the beam size of the laser before coupling it to the fiber can increase the coupling efficiency of it. Can I know why is this so? Maybe the fiber is of very small diameter, and the focal lens in front of the fiber can't focus all the laser to this small diameter...

A 10%-efficient car engine accelerates the 1700 kg car from rest to 18 m/s. How much energy is transferred to the engine by burning gasoline? What should be my first step in attempting this problem?

Does anybody know of an equation or rule of thumb for power decrease as load increases? As an example an electric golf cart will go say 15mph with one 100lb driver. Put 4, 200lb people in it and it will go much slower, say 9mph. Is there a way to determine what that loss will be other than...