Efficiency Definition and 901 Threads

Please help me with the question below with a proper explanation and also suggest me a reference to read for the same. Thank you! A solar collector receiving solar radiation at the rate of 0.6 kW/m2 transforms it to the internal energy of a fluid at an overall efficiency of 50%. The fluid...

I've be looking at the specs for Heat Recovery Ventilators (HRV). They commonly state that they can recover 85% of the heat. How is that possible? To me you could only every recover 50% in a perfect situation because of the equal volume of airflow's. Won't the air temperatures just stop at...

Thank you in advance for your help!What is the bandwidth efficiency (R/B) of PSK for a bit error rate of 10^-7 on a channel with an S/N of 12 dB?[/b] From the graph, for BER= 10^-7, Eb/N0 = 11.2 dB./b]I have applied the formulae Eb/N0 = S/N * B/R Where, S/N is Signal power over noise power *...

Hi I am trying to calculate the efficiency of my DC motor. I know that efficiency is: Power Out / Power In * 100 I have been told by my teacher that Power In is calculated by the following formula, Power In = Power * Time And Power Out is; Power Out = Mass * Gravity * Height...

Hi, I'm not sure if this is the correct sub-forum to post this question, so I apologize in advance if this post is misplaced. Anyways, a little about my self: I'm a Junior in high school, My passion is in physics and mathematics and I plan to major in physics and preferably get a PHD in it...

Not sure if this should be posted in the general physics forums or in the hw/coursework section. I'm in my second semester of general physics and have to do a class project. For my project I built an alpha type Stirling engine. In the paper I need to write I need to explain how it works using...

A question is being asked about a combustion chamber that has a moving piston; "an engine." "Which expression expresses the efficiency of the engine?" The answer given is: (Pressure(from burning))(Volume)/(moles)(delta H) While this looks some thing like PV = nRT, I don't fully understand...

Not sure if this is the right section for this, I apologize in advance. I have a project to do and my goal is to measure the efficiency of a solar cell INDIRECTLY. I am not sure how to do that. The equation for the efficiency of a solar cell is η = P/E*A. Where P is the cells...

By the conservation of energy, P_in=P_out So,no matter what gear ratio 'i' I choose, P_out=P_in, since the gear ratio 'i' term would get canceled at the numerator and denominator. $$P_{eng}= ω_{eng} M_{eng}= i . ω_{out} \frac{M_{out}}{i}$$ hence P_in=P_out But, what is the drivetrain...

Hi I've been looking in google although I can't find a definitive answer, what are the usual efficiency range for alternators, some talk about brushed ones in the range of 50 to 60 % , brushelss some say go as highas 75%, maybe some of you folks know from your experience what are the typical...

In hilly areas temp is low than plain areas.So the temperature of source as well as sink must be low.But ratio remains same.So efficiency is same as in plain areas? Is my logic correct? Or anything else? Can it be more?

efficiency -- how to get the maximum efficiency in a circuit? Homework Statement I don't quite understand how to get the maximum efficiency in a circuit. Exemple. 4 Volts and 2.0Ω will produce 8 watts with a current of 2.0 amps. 5 Volts and 3.1Ω will produce 8 watts with a current of...

Hi, I am trying to figure out how Li-Ion batteries operate in regards to efficiency. I understand they have rated voltage and current etc. and to operate them at these parameters if possible. However, I'm wondering is it simply the current that has effect on their efficiency. By Efficiency I...

So we've been doing fins in class. I understand that the formulas for fin effectiveness and efficiency are similar, except the area used in the denominator (Ac i.e. area of cross-section for effectiveness and As i.e. surface area for efficiency). However, my question is while designing a...

Homework Statement The Clapeyron cycle efficiency is similar to the Carnot cycle except that two adiabatic paths are replaced with isobaric processes a) based on the above information, draw a Clapeyron cycle. b)Derive the efficiency of the reversible Clapeyron cycle Homework...

Hi, all I'm seeking advice on how to calculate the energy conversion efficiency, in case of heat from light energy. I think that one of the general formulas 'energy output/energy input' can not be applied in this problem. Assuming that light(or laser) has 10W power output and material 1...

My classmates and I are working on a senior design project where we optimize a baseline turbofan for supersonic cruise. We are a little confused about when to use polytropic vs isentropic efficiencies. I have read to begin with isentropic, however is there anyone who could explain a little more...

Homework Statement A Carnot engine operates between a warmer reservoir at a temperature T1 and a cooler reservoir at a temperature T2. It is found that increasing the temperature of the warmer reservoir by a factor of 2.00 while keeping the same temperature for the cooler reservoir increases...

can we convert the linear motion into rotational motion in cars using a fly wheel under the car ?

Dear all, How is the efficiency of piezoelectric transformer higher than electromechanical coupling factor? Thank you, Husain

Is Carnot efficiency the same as thermal efficiency?

Is regenerative brake technology available on vehicles other than ecars and ebikes.if so what is the maximum efficiency reached till now on bikes and cars.

Homework Statement One of your friends is building his own airplane. He has received a quotation for a two-bladed propeller with an efficiency of ##\eta = 80\%## . He asks for your advice on whether it is possible to get a higher efficiency - what is your answer? no, the efficiency based on...

Homework Statement You build a heat engine that takes 1.00 mol of an ideal diatomic gas through the cycle abc, where segment bc is isobaric and segment ca is isochoric. calculate the thermal efficiency of the engine. this is a 5 part problem and I already solved for Wo and Wo=Qo I solved...

Hello, Homework Statement Engine A receives four times more input heat, produces six times more work, and rejects three times more heat than engine B. Find the efficiency of (a) engine A and (b) engine B. Homework Equations e = |W|/|QH| e = 1 - |Qc|/|QH| The Attempt at a...

Homework Statement Determine the amount of time it will take a 1000 W electric kettle to heat up 1.0 L of water to boiling point if the water starts at 10 °C and the kettle is made from 400 g of iron. The transfer of heat energy from the kettle to the water is 63%.Homework Equations P = W/Δt Q...

I am in an introductory physics class and we have been working with Gravitational Potential Energy, Elastic Potential Energy, Kinetic Energy and the Law of Conservation of Energy in relation to bungee cords. Recently, we delved into the topic of efficiency and with it I came upon the following...

Homework Statement Helium in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under air standard conditions, the thermal efficiency of this cycle is: a) 79.5% b) 20.5% c) 61.4% d) 67.4% e) 84.3%...

So I was looking through the internet on how one could improve the efficiency of a vacuum system (with a diffusion pump). Lots of websites describe systems with, cold traps to remove condensable vapors such as water. If I am not mistaken, cold traps also help prevent back streaming, similar...

Hello Everybody, Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given wing...

Hello Everybody, Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given...

1. 100kg of methane is compressed from 0.5MPa and 300K to 3.0Mpa and 500K in a closed chamber by a compressor. The compression process is assumed to be adiabatic, calculate the efficiency of this compressor. Specific heat capacity of methane under constant pressure is 35.58 kJ/k.mol.K and ideal...

Question as the title above ! Could we use the wind turbine to compress the air into engine cylinder as the exhaust compression tubine does ? Thanks all for replying !

Homework Statement An incandescent bulb is only 5.0% efficient. How much waste thermal energy is porudced by a 100.0W bulb in 1.0h? (Anwer=95J)Homework Equations P = E/T Efficiency = Eout/Ein x 100%The Attempt at a Solution P = E/T E = PT...

Homework Statement A golf club with 65 J of kinetic energy strikes a stationary golf ball with a mass of 46 g. The energy transfer is only 20% efficient. Calculate the initial speed of the golf ball. Homework Equations efficiency = E out/E in x 100% The Attempt at a Solution I...

Homework Statement If 230 million tonnes of solid waste were burned in waste-to-energy power plants that are 20% efficient a) how many kilowatt- hours of electrical energy could be produced in a year? Compare this quantity with the total US electrical energy production of 3.8 trillion...

Homework Statement In a race, a 54 kg athlete runs from rest to a speed of 11m/s on a flat surface. The athlete's body has an efficiency of 85% during the run. How much input energy did the athlete provide? Homework Equations efficiency = E out/E in x 100% The Attempt at a Solution...

The question: A perfect gas undergoes the following cyclic processes: State 1 to 2 cooling at constant pressure. State 2 to 3 heating at constant volume. State 3 to 1 adiabatic expansion. Deduce an expression for the thermal efficiency of the cycle in terms of r the...

Homework Statement A heat engine takes in 1030 J of energy at 1000 K and exhausts 585 J at 250 K. What are the actual and maximum theoretical efficiencies of this heat engine? Homework Equations For maximum efficiency I got 75 % by taking 1 - (250K / 1000K). For actual efficiency the...

Hi, I'm attempting to make a model of a DC motor capable of calculating the efficiency of the motor for different values for torque. I have managed to make a code to generate the torque-speed-power plots for given inputs, however I have been unable to figure out how to calculate the...

Homework Statement The controversial Cheviot open-pit coal mine in Alberta, Canada occupies 7,455 hectares (one hectare= 10^4 m^2) and produces 1.4 million tonnes of coal per year. a) use the energy content of coal of 29 MJ/kg to find the power in watts corresponding to this rate of...

Homework Statement A household uses 100 gallons of hot water per day (1 gallon of water has a mass of 3.78 kg) and the water temperature must be raised from 10°C to 50°C a) find the average power needed to heat the water. b)Then assume you have solar collectors with 55% average...

1. i drop a ball (mass 20 grammes) from a height of 10 meters, after 3 bounces it rises to a height of 2 meters, what is the energy conversion efficiency of each bounce? 2. I've been stuck on this for the last hour and have nothing any help would be great. 3.the closest i got was...

1. Problem statement A power plant generates electricity from the difference in sea temperature. At the surface of the sea the temperature is 27°C. At the bottom of the sea the temperature is 6°C. a) What is the highest efficiency that this plant can have? b) If the power plant generates...

I just got my hands on a solar battery charger with a set of usage specifications that makes me believe it will only be useful some four days a month and will take more or less such time to charge a single set of batteries, despite promises on the contrary in the instructions. Since the case is...

Hello, I'm trying to compare efficiency of different hydraulic motors by looking at unit of output per unit of input, viz: \frac{rpm × torque}{pressure × flow} I'm a bit flummoxed by one set of motor specs, for Eaton Duraforce motors, which is attached below. these motors seem to...

Homework Statement Four thermodynamic processes A,B,C,D are shown in the picture. A and C are adiabatic processes. Pressure is held constant during B, and volume is constant during D. An engine run from A->B->C->D->... What is the efficiency of this engine (in terms of V1/V2)? Homework...

Hi PF Somebody gave me this link could you help me to understand why (9) has to be inserted in (7) when the efficiency \eta < 1?

In many textbooks, a proof is provided where the work output of a super-efficient heat engine is provided to a carnot refrigerator, with the net result that a spontaneous heat transfer occurs from the cold reservoir to a hot reservoir. Let's use some numbers, TH = 600 K and TL = 300 K, so...

Is there a physicist who has discovered this, and could you explain how he/she did it? I was trying to find it on the internet, but it only gives me a lab review of load vs efficiency. thank you