Efficiency Definition and 901 Threads

The qwustion is: 2 identical cars with their engine rev 2000rpm. The only difference is that car num #1 is in 4th gear and car num #2 is in 3rd. Which car will use more fuel per minute? Considering they are driving on leveled ground. And does it Make a difference if they are going uphill...

An electric motor drives an electric generator.The 2hp motor draws 15A from a 120V D.C source and the generator supplies 5A to a 48Ohm LOAD. It is given that 1hp= 745.7W Calculate the motor efficiency. Calculate the generator efficiency. Calculate overall efficiency. Ok soo I...

I'm trying to calculate the heat loss of efficiency due to increasing the mixture of propylene glycol in a heat transfer fluid compared to water.. For this I'm saying that water has a heat transfer efficiency of 100% (relative only) Im looking for multiple data points to create an equation...

When I calculate efficiency of a transformer, I use output power/imput power x100%. Then what are these power values? Is the power the power in a load or the total power coming out of the transformer (meaning it includes the joule heating)? Then also what about the input power, which values do I...

Homework Statement Hey I've attached the question. My main problem is figuring out how to start. Homework Equations not exactly sure, PE=mgh? efficiency= used power/total power *100 = used power/ 2950 * 100... The Attempt at a Solution i calculated the potential energy...

Would the efficiency calculated using the P output/P input x 100 get the same answer as calculating the efficiency using the RMS input and output values? If so why?

Ok, I have a primary and secondary coil. I set up a transformer between them. Each has 400 turns of coil(N). The primary coil produces a potential difference of 2.988 V. The secondary coil has a potential difference of 0.0551 V. For the efficiency, I used the equation (Np*Vs)/(Ns*Vp) * 100%...

Is it true that a full wave rectifier is more efficient than a half wave and if so why?

Hello all! I chose not to follow the given format, as my question is kind of unique. I hate to be one of those people who just create an account for one thread (as I usually try to avoid this), but my situation is quite urgent. I have a project due Friday, in which I plan to take different...

I have made an Ottos Cycle graph and found the area Wnet and W12. I now have to find the efficiency η = Wnet/W12 I have found that to be 0,20 but I have no idea what this tells me about the work or anything. I need help.

Hi, Given value of top and bottom temperatures can anyone explain why the Ideal Carnot Cycle is more efficient than the Rankine cycle but why the Rankine is the preferred model? I know that in the Carnot the pump would have to be able to deal with a mixture of steam and water and the turbine...

What is the heating efficiency of a domestic induction heater as compared to a simple electrical heater and microwave oven? Please give comparison on the basis of Kilowatt hour consumed.

Hello, I've just been playing around with a 2n3904 transistor and 3V coin battery. I noticed when powering an LED with a transistor switch the LED is significantly dimmer than when powering the LED directly. Why is this? Is it because 0.7 volts is siphoned off just to turn the transistor on?

Homework Statement Consider a homeowner who is replacing his 25-year-old natural gas furnace that has an efficiency of 55 percent. The homeowner is considering a conventional furnace that has an efficiency of 82 percent and costs $1600 and a high-efficiency furnace that has an efficiency of...

Homework Statement I'm on my last question for my coursework and this is it. I have managed to find out how to calculate the efficiency of a pulley but not "what is the efficiency of a pulley" Could someone please help me. Homework Equations Efficiency = (Mechanical Advantage /...

Homework Statement A pulley system has an efficiency of 71.5 percent. How much of the rope must be pulled in if a force of 641 N is needed to lift a 160 kg desk 2.51 meters? Homework Equations IMA = De/Dr MA = Fr/Fe Efficiency (%) = Wo/Wi Efficiency (%) = MA/IMA I have absolutely...

Googling for information on the topic leads me to graphs such as this, which suggest that if Beta and advance are optimal efficiency tops out at 85% or so. Some questions: 1) Is the ~15% lost energy converted to heat, or is there some stray kinetic energy in airflow that is somehow unusable as...

I'm tasked with creating an egg protector that bounces. I'm thinking of gluing bouncy balls together side-by-side around a template sphere. The glue being used should be very strong, it's a super glue that works on rubber. Would this be able to bounce effectively? Will I need to add mass...

Lets say if we have an induction motor or any motor whose rotating shaft acts as a source of alternating emf to another motor and rotating shaft of this motor again acts as a source of alternating emf to third motor and so on... We connect such a finite number of motors and we call it as a...

Hi evry1! Just wanted to know that which has got higher efficiency - 2 stroke diesel engine or 4 stroke diesel engine. I believe that direct injection of fuel in diesel engines prevents the loss of unburnt fuel in exhust of 2S engine. And simpler mechanism and lesser no. of moving parts in 2S...

Homework Statement A reversible engine contains 0.5 mol of an ideal monatomic gas and operates using a cycle, similar to that shown in Fig. 19.21 on page 324 of the textbook, consisting of constant volume and constant pressure segments. (You will need to draw your own diagram using the data...

http://a6.sphotos.ak.fbcdn.net/hphotos-ak-ash4/388044_10150449591037412_816037411_8386849_1415117382_n.jpg Homework Statement A ramp system is set up. Due to friction the ramp has an efficiency of 82%. Two cars of equal mass are allowed to collide and car 1 starts from rest at height h1...

Homework Statement While running up stairs at a (vertical) rate of 0.30 m/s, a man of 70 kg generates waste heat at a rate of 1300 J/s. What efficiency for the human body can you deduce from this? Homework Equations efficiency of heat...

Homework Statement A 52-kg mountain climber, starting from rest, climbs a vertical distance of 730 m. At the top, she is again at rest. In the process, her body generates 4.1 × 10^10 J of energy via metabolic processes. In fact, her body acts like a heat engine, the efficiency of which is...

In M-ary psk Rb=Rs*log M log with base 2 Rb- bit rate Rs - symbol rate then bandwidth required for passband signal is B=Rs and bandwidth effeciency = Rb/B=log M log with base 2. Is the above formula for bandwidth efficiency...

Homework Statement The PV diagram below (I will describe it) shows a cycle for 4.87moels of an ideal gas. The path ab is along an isothermal line. Pressure is in atm and volume in m3 Point a: (.08, 6) Point b: (.24,2) Point c: (.08, 2) Find the ideal and the actual efficiency of...

Homework Statement A 2.0x10^2 g pendulum bob is raised 22cm above its rest position.The bob is released, and it reaches its maximum speed as it passes the rest position. Calculate its maximum speed at that point by applying the law of conservation of energy and assuming that the efficiency...

Homework Statement Joe ascends a small hill from an elevation of 250m to an elevation of 490m. In doing so he expends 2.8x10^5J. If Joe's mass is 75kg what is the efficiency of his climb? Homework Equations W= change in E= change in Ek + change in Ep Ep= mgh Ek= 0.5mv^2...

Homework Statement I am using a 5 kilowatt motor to pump oil to a holding tank which is 20 m above the pump. If the motor is 65% efficient, how many liters of oil can i pump per minute if 1 liter of oil has a mass of 1.30 kg?Homework Equations ?The Attempt at a Solution ?

Hello forum, what is the main difference between max power transfer and max power efficiency? In the case of max power transfer, the goal is to transfer the most energy to the load per unit time (impedance matching). Power is I*V and is about delivering energy very fast... High power...

Homework Statement I'm trying to find an expression for the efficiency of a stirling engine operating with an ideal diatomic gas, and cycling through a volume V and a multiple of its compression ratio, r, Vr. Homework Equations processes: 1-2 isothermal expansion 2-3 isochoric...

A transformer is rated at 2300/230 V, 15 kVA and 50 Hz. Assume that the transformer is operating at 80% p.f., leading and at rated output the secondary terminal voltage is 230 V. The following parameters for the transformer are given: N1 = 1500 turns N2 = 150 turns r1 = 2.7 ohms r2 = 0.024...

We were assigned a problem in class, but because it was on guest lecturer material, I am unclear of which given numbers and what equations to use. I do know I am supposed to use: η=TH-Tc/TH But I am confused as to why I have been given 4 variables ...Please Help! Here is the question [1] You...

Air at 1175 K, 8 bar enters a turbine operating at steady state and expands adiabatically to 1 bar. The isentropic turbine efficiency is 92%. Employing the ideal gas model with k=1.4 for the air, determine (a) the work developed by the turbine, in kJ per kg of air flowing, and (b) the...

The efficiency to which I am referring is the amount of mass converted to energy. I need to find an academic source to cite that fusion is more efficient in this respect than fission. Any sources?

I've read (I think it was on slashdot) that using constant velocity cruise control on your car is much more energy efficient than letting your speed vary. To the point where they said you would want to control your speed to much less than 1 kph. What is the general consensus on this? I'm a...

Given a flexible, inelastic and incompressible string of radius R, how much at most would it shorten from tying an overhand knot in it?

set up 12v bat. to 150w inverter to a tower pc. so i put a amp meter between 12v bat and inverter .times the volts by amps get wattage? then get the wattage of computer using a mains socket(because the inverter produces modified sinewave and my wattage meter may not work...

This is the question that I can't really answer 1. A cycle looks like an ellipse in the T-S diagram. The maximum and minimum temperatures are 1000K and 400K. The maximum and minimum entropies are 0.705 KJ/K and 0.235 Kj/K. Determine a. the heat added per cycle, b. the work produced per...

Hello to you all, Does anyone know if gas engines running on a cogeneration (combined heat & power) mode can achieve electrical efficiency rates as high as 40% as it is...

I am trying to have students build a tester with sourceMeter, lamp, etc. for solar cell efficiency measurement. Could someone give me advice on this project? Thank you very much.

Homework Statement I have attached the question. I'm not really sure how to do this one Homework Equations power = work done/time The Attempt at a Solution Is the turbine efficiency simply the power generation (750kW) divided by the mechanical output (800kW) which is so 750/800 x...

Does the efficiency of a gearbox just reduce the torque output of the motor? Or does it also reduce the speed? For example I have a motor with 100 N*m torque at 100 RPM, it then goes into a gearbox with a 80% efficiency and a 2:1 ratio. So the torque would be 2*100*0.8 Nm and the RPM 100/2...

Hi, I am working on this project that has to involve physics, chemistry and biology. The chemists in my group will be performing an experiment to measure the enthalpy of combustion of three different fuels: alcohol, diesel and petrol. My task as a physicist is to, using their results...

Does anybody have any numbers for this new discovery? http://web.mit.edu/newsoffice/2011/sun-free-photovoltaics-0728.html How much of the heat is converted into electricity by a standard thermoelectric power plant? And how much of the heat is converted into electricity by this new device?

There are rumors circulating recently on various forums on the internet that a net made of coiled up silver wires increases the efficiency of a gas range when placed on top of the gas burner while fuel is being burned. According to what manufacturers claim, this is done by using the reaction of...

OK so i know it is possible to double the frequency of a light beam by using second harmonic generation by passing the beam through a non-linear crystal; however i am unclear as to the required intensity of light beam that is needed to achieve efficient conversation. Would it be possible to...

If one was to make a pulley to lift something massive like a ship, I am assuming the masses involved of the ship and the counterweight, will mean decreased efficiency due to : 1. Higher friction between in the sheave and axel area. 2. larger cable/robe mass on the longer end (once the pulley...

Would the efficiency gained in an orbital Solar generating facility be mitigated by some/degree of diffusion loss when transmitting, say by microwave. through an atmosphere? Is the rate of efficiency growth in solar panels comparable to that of computer chips? (I think the answer is no). And...

I know people from countries where they just shoot the bad guys. Not much for trials & justice. We spend a lot on housing prisoners in the US. How can the efficiency be improved? [SIZE="1"]Disclaimer: sorry for not creating yet another left-vs-right thread.