Efficiency Definition and 901 Threads

Homework Statement A ball that weights 1kg is thrown in the air, the hand being 1m above the ground. The velocity the ball was thrown at was 14m/s and it's maximum height was 6.5m above the ground. What is the efficiency for this energy transformation? Homework Equations Do I just get the...

Hi, [FONT=PT Sans] I'm trying to figure which is more fuel efficient, turbine vs stroke generators. This honda stroke engine generator does 1000w for 3.8 hrs with 0.6 gallons of fuel or 2.3 liters, so the power per liter of fuel is 1,300 kW...

Homework Statement Is it possible to calculate the work done heat transfer, and efficiency of an object in a thermodynamic system, given the Temperature vs Entropy graph? Example: Homework Equations ∆U=Q-W ∆S=dQ/T e=1-(Qc/Qh) e=W/QhThe Attempt at a Solution Since this is a T vs S diagram,i...

I'm struggling to understand the Carnot efficiency. I can follow proofs that prove efficiency= 1- (Th/Tc), and I understand the nature of the processes that make up a carnot cycle - however I still can't make sense of it in my head. I've looked online and most people try and explain it...

Hi, When the modern 80 plus power supplies are quoted as being "87% efficient" on 100% load, does this mean that an 80 plus Gold PSU rated at for example 1000 Watts will provide 1000 Watts to the internal PC components, and therefore draw 1000/(0.87) = 1149.43 W from the wall? OR does it mean...

I regret to say that I know little of engineering, but, to make a long story short, I'm nagged by two questions about energy conversion efficiency. There is a thread i made titled "giant railguns recycling their own energy in space" in the science fiction & fantasy forum here that explains my...

The efficiency of a Carnot Engine is described by the relationship: Tc/Th = Qc/Qh, so that e(Carnot) = 1 - Tc/Th For heat engines, can their efficiency also be related to temperature as well? Or is the description of their efficiency just: e(heat engine) = W / Qh = 1 - Qc/Qh I am inclined to...

Q1. I know a DMM will anticipate a sineusoidal supply, thus there can be problems with spiky supplies. Even if you have a true RMS meter, it it's a spikey supply, non-sineusoidal, you still can't calculate the peak of a spiky supply? Does a DMM measure the peak, then calculate from THAT the...

Energy efficiency related question: please help with an anwer to the following: Given a flat electrical coil of known dimentions, this coil is used as an induction coil, laid flat, on top of the cooking surface of an induction cooker. Basically, the induction cooker has a copper braided coil...

What information can one obtain from the plots of the background vs signal efficiency? \epsilon_{bkg}(\epsilon_{sig})? In particular I attach some plots I made by hand and I want to understand how to obtain what each tells us.

Hello, I've been trying to wrap my head around this topic and came across such a thread here: https://www.physicsforums.com/threads/propulsive-efficiency.643646/ but still don't get it. Why is it that that accelerating one unit of mass by two units less efficient than accelerating two units of...

I was told that "piezoelectric materials can become more efficient if they were made to reduce their elasticity (the ones such as PVDF films that are flexiable).This is because the external energy is used to force the film back to its original shape just like when a spring is squashed; so most...

In the proof of Clausius inequality ##\oint\frac{\delta Q}{T}<0## for an irreversible cycle, I always find the fact that the thermal efficiency of an irreversible machine is **stricly less** than the thermal efficiency of a reversible machine, both operating between temperatures ##T_H## and...

The efficiency of a scientific camera like http://www.princetoninstruments.com/products/imcam/proem/ is specified by the quantum efficiency vs wavelength. The meaning is simple enough. Assuming a fill factor of 1, it's the fraction of incident photons that generate a charge. But photographer...

[Moderator's note: Recategorized thread to "Basic".] While driving alone through the beautiful scenery of Banff and Yoho national parks, a question formed in my mind. Which of these modes of slowing down a vehicle by an equal amount is likely to minimize the resulting overall increase in...

Recently I've been in a discussion with someone online who claimed that the efficiency of a computer with regards to energy is not a linear relationship. I assumed that if you were to halve the power going into a computer chip (assuming it was designed to deal with that and wouldn't just turn...

Homework Statement An "energy bar" contains 22 g of carbohydrates. If the energy bar was his only fuel, how far could a 68 kg person walk at 5 km/h? Mass(person) = 68 kg; v = 5km/h; 22g carb = 4 Cal/1 carb = 88 Cal; P(power of man walking) = 380W (this is derived from my textbook). Homework...

"A Faraday cage or Faraday shield is an enclosure formed by conductive material or by a mesh of such material. Such an enclosure blocks external static and non-static electric fields by channeling electricity along and around, but not through, the mesh, providing constant voltage on all sides of...

I tried to calculate the efficiency of a engine using the formula : Efficiency = (Net Work Done) / (Heat absorbed) And then I tried to calculate the efficiency of respective Carnot engine by two ways : 1) Efficiency = (Net Work Done) / (Heat absorbed) 2) Efficiency = 1 - (Temperature Lowest /...

Hi, so I was wondering about how the car's LED, MP3/IPOD, AC systems consumes up electrical power and then to fuel? Let's say that the loads are running for 5-7 hours. Thanks for the replies/ideas!

How to calculate the efficiency of a generator? Any formulas?

Which one do you think that is more efficient? I think that lecturers, from the fact of being humans, commit more mistakes than books when they give information because they can forget to transmit important details. Books are written carefully in order to be easy to understand, what's said was...

" A intelligence signal is amplified by a 80% efficient amplifier before being combined with a 12kW carrier to generate the AM signal. if it is desired to operate at 100% modulation, what is the DC input power at the modulator" The choices are a: 12kW b. 7.14kW c.7.5kW d. 15kW my solution...

I reference this forum all the time and you guys are always good at breaking down confusing questions so I decided I needed to make an account and get some help with a mental struggle I have been having for quite some time! Two commonly discussed ways of improving a compressor's efficiency in a...

Homework Statement Can the power efficiency of the domestic hair dryer be improved by reducing the heat energy and increasing airflow? Homework EquationsThe Attempt at a Solution

Homework Statement Hi! I have a problem with the following problem: Calculate the efficiency of the solar cells with the characteristics given in the table below Power (28 degrees, BOL): 300 W/m2 Absorptance: <91 , emittance: >82. Reliability: 0.999 . Mass: 2 kg Homework Equations I know...

(b) An energy audit was conducted on a building to demonstrate energy savings opportunities by replacing the air handling unit or AHU fans motors, condensing and chilled water pump motors of the water cooled chilled water air-conditioning installation with newer, more efficient motors of the...

I'm constructing a quantum circuit that implements a gray code that connects the binary strings |0001> and |1110> using CNOT gates. Since the two strings are negations of each other, two equivalent circuits can be designed where the control qubit conditions are negated. My question is what is...

Homework Statement In a 30% efficient, -16°C fridge, how much electrical energy will be used up to lower the temperature of 250 mL of 75°C water? If the fridge is rated at 150 W, how long will this process take? Specific Heat Capacity of Water = 4200 J/Kg×K Specific Heat Capacity of Ice = 2000...

Is the efficiency of a cell in a closed circuit always 50%?

I can't realize the proving why Carnot engine has the highest efficiency. "Let εc be the efficiency of a Carnot engine operating between two given temperatures.If an engine X, which has an efficiency εx that is greater than εc.We can couple engine X to a Carnot refrigerator , and they make a...

Homework Statement The oxygen contained in a thermally insulated container will be cooled down to its boiling point (-183 C), and then condensed. Thereby one uses a reverse Carnot process operating between the oxygen gas (instantaneous) temperature and the room temperature (17 C). What is the...

Changing the potential energy of water is frequently used as a means of storing excess renewable energy when it is not needed and using it when it is needed. An electrically-powered pump with efficiency 62 % raises a 10 kg mass of water a height of 10 m. The water is subsequently allowed to...

Hey guys I was wondering what would happen if: took a ball neo magnet, balanced it on a few other magnets to basically make it a frictionless bearing. Then spin the ball magnet to 10k rpm. But do all this in a box that's a vacuum. Would the neo ball magnet spin basically for a VERY long...

Homework Statement A possible ideal-gas cycle operates as follows: (i) from an initial state (p1,V1), the gas is cooled at constant pressure to (p1,V2) (ii) the gas is heated at constant volume to (p2,V2) (iii) the gas expands adiabatically back to (p1,V1). Assuming constant heat capacities...

I am doing an experiment to determine the performance of a steam plant cycle and analyse it in comparison with the ideal rankine cycle. I have a sketch of the actual and real T-S diagram for the steam plant (See attached) I am unsure what factors cause the change in the shape of the T-S...

Hello all, this is my first time posting here so please excuse if this maybe isn't the appropriate thread to post this in but I figured it may be the most relevant. I am working on writing a proposal (small, just 450 words), that aims to address the energy efficiency of a university, ie...

Homework Statement Figure 2 represents a model for the thermodynamic cycle of the Stirling engine, patented by Scottish clergyman Robert Stirling in 1816. The engine operates by burning fuel externally to warm one of its two cylinders. A xed quantity of inert gas moves cyclically between the...

1-Is the efficiency of heat engines working in cycles other than Carnot independent of the nature of substance used? Can we still claim that maximum efficiency in converting heat to work is attained during reversible processes for such cycles? For which engines/cycles can we do this? 2- Why is...

hello we know that there is 42% limitation in the efficiency of internal combustion engine, thermodynamically calculated by Carnot and we can never overcome this can someone explain me in few simple words why this is true? also, does this apply to the energy from internal combustion to...

Greetings. I was wondering if anyone knew of a way to calculate the efficiency of Newton's Method for a given function: I have an equation f(x) and I'm trying to find a value of x = x0 such that f(x0) = 0. So I start with a guess x0 and then use that to find a second (usually closer) guess...

Homework Statement Transformer efficiency loss Homework Equations Larger transformers are more efficient than smaller The Attempt at a Solution I understand the basics of energy loss through heat etc but i don't understand why it would be different for the sizes of transformers. Is it to do...

So, I'm doing this coursework right now, and I know that this equation is what's needed to get to the efficiency but I have only a little idea why. I'm given this formula...

can anyone suggest me the sites where i can find the methods to improve the efficiency of IC engines?

The thermodynamic efficiency ##\eta## is calculated by ##\eta= \frac{W_{out}}{Q_{in}}## Using the first law of thermodynamics we usually say that ##W_{out}## is ##Q_c+Q_h##, where ##Q_c## is the heat dissipated into a cold reservoir, and ##Q_h## is the heat absorbed by the system because of a...

Homework Statement I read here http://www.engineeringtoolbox.com/pump-system-curves-d_635.html that this is where the system curve and the pump performance curve intersect. But if the situation involves pumps in series, what will the system curve be a plot of? Is it flow rate and the total...

Hi, Is there a difference in efficiency between a three phase motor and a single phase motor, in terms of power in against power out. If so, could you please explain why one is more efficient than the other. The reason I ask is because I'm researching the development of the induction motor for...

Homework Statement The efficiency of a heat machine is ##E=\frac{Q_2-Q_1}{Q_2}## where Q2 is the heat inserted because of the explosion and Q1 is the heat that leaves through the exhaust. It says in the book that E can be derived from the volumes ratio V1/V2: $$E=1-\frac{1}{\left(V_1/V_2...

I just wanted to know when we throw something like a ball up inside a moving car, the weight of that ball till it is air is 0 on the car.Does it mean that the car has become lighter and will take less energy to run.I know the effect is every small but please tell the answer.

Hello, concerning power supplies. I am at the stage where all the components are ready except for the batteries. The thing is, not all the components have the same voltage. My first thought was using a high voltage battery connected to a custom made Power Distribution Board which splits and...