Efficiency Definition and 901 Threads

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...

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...

Homework Statement A heat engine using 5.00 g of helium gas is initially at STP. The gas goes through the following closed cycle: - Isothermal compression until the volume is halved. - Isobaric expansion until the volume is restored to its initial value. - Isochoric cooling until the pressure...

Efficiency is essentially the ratio of what you get to what you put in. COP also seems to represents the same thing (i.e. COP of a refrigerator is Ql / W, which is the amount of heat removed / the amount of work done to remove it). I know efficiency cannot exceed 1, but how come COP can have...

Homework Statement A hypothetical engine, with an ideal gas as the working substance, operates on the cycle shown in Figure 1. Show that the efficiency of this engine is e = 1 - \frac{1}{\gamma}\left(\frac{1 - \frac{p_3}{p_1}}{1 - \frac{v_3}{v_1}}\right) Where \gamma =...

Homework Statement A heat engine takes 4.0 moles of an ideal gas through the reversible cycle abca, on the pV diagram, as shown. The path bc is an isothermal process. The temperature at c is 600 K and the volumes at a and c are 0.04 m^3 and 0.10m^3, respectively. The molar heat capacity at...

if a engine must do 500 joules of work to pull a 10 kg load up to a height of 4 meters, what is the efficiency of the engine?

I'm having a bit of difficulty figuring out the theoretical efficiency of a compound epicyclic gear train. The math involved is a bit over my head. This train is meant to run at very slow speed under light load. I want to find the theoretical efficiency of the design so I can determine if it is...

I have a project for my sophomore design class to test the efficiency of a wobbler steam engine. I have heard people talk of using a dc motor and connecting it with a belt to the flywheel to see what voltage it produces but I don't know how to do that. In addtion, some have suggested to just...

Homework Statement It is required to design a single acting twin cylinder air compressor to deliver 17.2kg/min of compressed air at 7.2 bar. The intake pressure and temperature are 1 bar and 15oC respectively. Compressor speed is to be 300 rpm. Take clearance volume as 5% of the swept...

I am seeking help with the theory of energy conversion from kinetic energy to electric energy. Is it possible to convert kinetic energy to electric energy at an efficiency higher than 75% If so, how? Specifically, I mean not using heat (cogeneration power plants) or potential energy...

Homework Statement A climber's gravitational potential energy increases from 14000 J to 21 000 J while climbing a cliff. She expends 18 000 J of energy during this activity. What is the efficiency of this process? Homework Equations Efficiency= useful output/ total input Total...

Homework Statement In one location, the average daily temperature varies sinusoidally between 35C in summer and 0C in winter. The ground temperature below 2 m underground is the annual average temperature. A heat pump / air conditioner unit must deliver air to a house at 30C in winter and...

It appears everyday electric space heaters, that is resistance heaters, are virtually 100% efficient. No matter what resistance material is used, there is only 3.413 BTU per watt hour of heat output; in other words, all 1500 watt heaters consume the same amount of electricity and produce the...

been reading in many books that polytropic efficiency is always recommended over isentropic efficiency. what are the advantages of using polytropic efficiency? what makes it different from isentropic efficiency? it is also told that polytropic efficiency is independent of pressure...

Something > Carnot efficiency ? WTF? So I've made a very simple, ideal model of a heat engine, and my calculations just don't match up to the carnot thing: efficiency = 1-(Tc/Th) It looks like this: I supposed a rectangular block, base of 1cm by 1cm, and a piston free to move up and down...

O.K. this is maybe a large question... I am trying to find out how much energy it would take to do the work of a heat pump compressor that would be required to heat a... let's say 10 ft. x 10 ft. room of a typical house. I know there are a lot of variable here... What I am trying to...

Homework Statement Calculate the maximum possible efficiency of a heat engine that uses surface lake water at 19°C as a source of heat and rejects waste heat to the water 0.100 km below the surface where the temperature is 4.1°C. Homework Equations eta = 1 - Tc / Th The Attempt at...

How does one calculate efficiency for an incandescent light bulb? Assume the bulb is 40 W, has a tungsten filament at temp. ~ 2800 K. The bulb would be used for heating in a device. If we assume blackbody: From Wien's displacement law, the maximum wavelength is 9.99E-7 m. Fromt the...

Homework Statement The power output of a car engine running at 1900 is 600 kilowatts per hour. How much work is done per cycle if the engine's thermal efficiency is 30.0 percent Homework Equations thermal efficiency=w(out)/Q(hot) The Attempt at a Solution It wants the answer in...

I wonder why water turbine (like in hydroelectric power plant) has, in most design, more then 90% efficiency when steam turbine around 30%. In both cases we converting the pressure to work, so why such a difference in efficiency?

Homework Statement The exhaust temperature of a Carnot heat engine is 121◦C. What is the intake temperature if the efficiency of the engine is 13.4 %? Answer in units of ◦C. Homework Equations e=1-(Tc/Th) The Attempt at a Solution This seems like just a plug and chug problem...

Homework Statement A 2.5kW electric kettle takes 3 mins to raise the temperature of 1.2kg of water from a temperature of 20 degrees C to a temperature of 100 degress. The specific heat capacity of water is 4.2kJ/(kg K) Homework Equations So far I know that we're either using P=vit ot...

In order to increase the diffraction efficiency of the AOM, we need to reduce the beam size of the laser. According to the manual of my AOM, it needs to have the beam size of 220um to get more than 90% diffraction efficiency. So, I decided to do so by putting a lens in front of it and...

1. Efficiency is defined as work-out/work-in. Muscles operate with an efficiency of about 20% in converting energy internally into work externally. Accordingly, how much energy will be expended by a 60 kg person in the process of ascending several flights of stairs to a height of 25 m...

I am planning to test the efficiency of Indian kino oil as a biodiesel... How do I do it? I only have access to my school chemistry lab...

A student performs an experiment in which an electric motor is used to lift a 200g weight through 2m, thus increasing its potential energy 4J. from measurements of the rate at which the weight is lifted the efficiency of the motor is to be determined. Two different voltages were used and the...

Hello, Does adding electrolyte increase the efficiency of h2o electrolysis? If so, is there a formula to figure out ideal electrolytes, etc? Does the electrolyte weaken the H2O covalent bonds, or just allow current to flow easier between electrodes? Thanks,

I know the formulas for efficiencies e of heat pump (it is e<=Tmax/(Tmax-Tmin)) and refrigerator (e<=Tmin/(Tmax-Tmin)), where Tmax and Tmin are temperatures of warmer and colder (respectively) involved containers. These formulas make me puzzled, as efficiencies seem to be possibly bigger than 1...

Hi, What is the cause of inefficiencies in single dish radio astronomy? I think it's related to the efficiency of the dish itself ...that the effective area of the dish is less than its total area. Is that right? If so, why is that the case? Thanks, San

uh...just wondering but how do you find out the efficiency from a P-V graph?

Homework Statement The figure represents a simplified PV diagram of the Joule ideal-gas cycle. All processes are quasi-static, and C_P is constant. Prove that the thermal efficiency of an engine performing this cycle is \eta = 1 - \gamma \frac{\frac{V_{1}}{V_{2}} - 1}{\frac{P_{3}}{P_{2}}...

Homework Statement The figure represents a simplified PV diagram of the Joule ideal-gas cycle. All processes are quasi-static, and C_P is constant. Prove that the thermal efficiency of an engine performing this cycle is 1 - \left(\frac{P_1}{P_2}\right)^\frac{\gamma - 1}{\gamma}...

Homework Statement Determine the efficiency for the cycle shown in the figure, using the definition. Assume that the gas in the cycle is ideal monatomic gas. Compare with the efficiency of a Carnot engine operating between the same temperature extremes. see attachment Homework...

Homework Statement A reversible engine contains 0.20 mol of ideal monatomic gas, initially at 600 K and confined to 2.0 L. The gas undergoes the following cycle: Isothermal expansion to 4.0 L. Isovolumic cooling to 300 K. Isothermal compression to 2.0 L. Isovolumic heating to 600 K...

Interesed in practical maximum efficiency of linear alternators. Suppose an object with a permanent magnetic attached moves along a linear track with a constant velocity, such that its kinetic energy is 1 joule. The object "collides" with a linear alternator or generator, such that the magnet...

Suppose there is an object with a permanent magnet attached to it that can slide on a linear track. The object is initially at rest and the permanent magnet alligns with the axis of an electro-magnet. If the electro-magnet is pulsed on momentarily with a current so that the object acquires a...

Tesla Motors claims a "well-to-wheel" efficiency of 1.14 http://www.teslamotors.com/efficiency/well_to_wheel.php" What in the blue blazes are they talking about?

guys. help me to explain this question.. The efficiency of nuclear powerplants used to produce electricity is about 40%. Under what condition this conversation efficiency could be increased to 100%? What difficulty might be encountered?thank you guys!

I live in a very hot climate. I have upgraded my windows to double pane thermal with some some success in cooling my home. I have been considering both additional fiberglass insulation and a radiant heat barrier for my attic as the air conditioning bill is still horrific and rates keep rising...

Homework Statement An ideal gas engine that works according to the following cycle. Find the efficiency of this engine assuming that the heat capacities of the gas may be taken to be constant. Recall that the efficiency may be defined as: \eta = \frac{Net work done over full cycle}{Heat...

Is 55°C best status for solar cells?