The power tag has no wiki summary.
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1answer
52 views
Calculating the mechanical power of a water pump
Say I want to pump water from one container to another. The water levels are 3 meters apart, and I want to pump 10 litres per hour. I figure the mechanical power necessary, assuming no losses, is:
$$
...
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1answer
64 views
How to understand the thermal radiation?
I am studying the thermal radiation (Stefan–Boltzmann law) by myself
$$P = \epsilon \sigma A T^4$$
here $\epsilon$ is the emissivity, $\sigma$ is Stefan-Boltzmann constant, $A$ is the surface area ...
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2answers
46 views
Light bulbs, Wattage meaning? [closed]
Light bulbs, Wattage meaning?
Two incandescent bulbs (120 V, 25 Watt) and (120 V, 500 Watt) connected to the same batteries.
Which one shines brighter? And why?
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2answers
189 views
How do you calculate power at the focal point of a mirror?
I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
3
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1answer
98 views
Is it possible to get energy from electrical wire using induction?
Pardon me if this is a stupid question but my physics courses are from a long long time ago and I was a teenager back then. ;)
Electricity in a wire generates electromagnetism, right?
Would it be ...
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2answers
67 views
Nuclear based wireless power?
I would like to ask if there is any Nuclear process which can be used to produce a wireless power ?
Is there any nuclear process can be radiate to the environment with no harm to human beings?
...
3
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1answer
261 views
Calculating displacement amplitude of ultrasonic power transducer
I am not a physicist, but my current project drives me to some physics-related computations, hence seeking help.
I have some ultrasonic transducers, 5938D-25LBPZT, for which very limited information ...
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6answers
536 views
When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it?
Consider these two situations when driving on a long straight road uphill:
Starting at a high velocity $v_h$, which the car is able to maintain.
Starting at a lower velocity $v_l$, and then trying ...
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2answers
284 views
Harvesting electricity in the air from power lines:
Recently I came across this quote on the internet, about a person who apparently set up devices to extract electricity from the "air", on his own property:
I read an article a couple of years ago ...
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2answers
404 views
Quantum Computing Power Advantages
Currently, the world's fastest supercomputer runs at 17.59 Petaflops, which consumes 9 megawatts of electricity. A qubit-based quantum computer has the potential to operate much more quickly for some ...
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3answers
92 views
Power of a runner
How can someone calculate the power in watt that a runner produces, when he runs uphill and downhill?
Is there any algorithm? It is important to take under consideration the uphill and downhill ...
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1answer
127 views
Is resistance to motion directly proportional to the speed of a moving object?
Power is known to be equal to the force x velocity (P=FV).
Im solving a question that states the following :
Car with engine working at 32 kW, mass of 1 tonne, travels at a constant speed of 40m/s ...
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2answers
178 views
Mechanics Question: Energy, Work and Power
I'm a pure mathematician by trade, and have been trying to teach myself A-level mechanics. (This is not homework, it is purely self-study.)
I've been working through the exercises and have come up ...
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1answer
122 views
Mechanics Question: Work and Power
I'm a pure mathematician by trade, but have been teaching myself classical mechanics. I've got to the chapter on Work, Energy and Power and I've found an example that is causing me some problems.
...
1
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1answer
51 views
Sound intensity and space/things in the way
Suppose you have two stationary people, A and B, who are equally effective in terms of hearing ability, and A emits a sound that is heard by B at a certain intensity. If they remain stationary, and B ...
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2answers
110 views
Averaging decibels
Wikipedia:
The decibel (dB) is a logarithmic unit that indicates the ratio of a
physical quantity (usually power or intensity) relative to a specified
or implied reference level.
If I ...
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2answers
504 views
Confusion about P=VI and V=IR
If we look at $P=VI$, we see that if the current doubles then the potential difference is halved
but this doesn't seem to make sense according to $V=IR$. If we look at that equation, since the ...
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6answers
336 views
Confused about unit of kilowatt hours
So I am a little confused on how to deal with the Kilowatt hours unit of power, I have only ever used Kilowatts and I have to design a residential fuel cell used as a backup generator for one day.
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2
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1answer
76 views
What are the properties and impediments of a liquid air fueled engine?
I recently came across a very interesting article that suggested the possibility of using liquified gases like air, nitrogen, or oxygen as a power source for cars. It appears that this company is ...
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2answers
105 views
Why do we need more power to do a job fast?
Let's assume we have two identical electric trains. One has a big electric motor (high power) and the other has small motor (low power). Let us assume the electric motors are of the same brand and ...
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1answer
320 views
Calculate the UPS Capacity in amp-hours [closed]
I am trying to find out the UPS capacity in amp-hours for my HP UPS system.
I've already done some calculations based on the UPS information from the HP Power Manager software.
Bellow are my ...
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1answer
195 views
What is the relation between fan blade and air flow CFM?
If I have a motor use in 2 cases, the 1st case I use standard blade and 20% longer blade in the 2nd case.
People told me that longer blade will create higher CFM. However, I am not totally sure. ...
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0answers
110 views
Antenna Power and gain calculation [closed]
I have a wireless security related question, the second part confused me:
Your wireless network usually has a range of 100 feet. However you
are having a (confidential) meeting in a 10’ x 10’ x ...
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2answers
397 views
An Ideal Transformer
In a transformer assumed to be transformer, power in the primary is equal to power in the secondary. So in a sense, the power in the secondary is 'fixed'. Output voltage in the secondary is also fixed ...
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4answers
679 views
Do resistor-based fan regulators save no power at all?
I have heard that the traditional resistor-based fan speed regulators are inefficient. In fact, I have noticed that such regulators tend to get hot when the fan is set to low speed. However, does that ...
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1answer
130 views
Power, Force Velocity
In any case, if the force and power is constant , does velocity also need to be constant? If no, can you tell me a case.
Further can this be extended for non-rigid bodies.
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2answers
616 views
What is the luminosity per square meter hitting the Earth's surface from the Sun?
So I know that the Sun's luminosity is $3.839 \cdot 10^{26}$.
What I want is the luminosity per square meter at the Earth's surface. So this is what I have got so far:
I know the distance to the ...
6
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3answers
470 views
why aren't there nuclear powered aircraft?
I know this might sound like more of an engineering question that about physics, and it probably is, but bear with me: i'm still not sure if the answer to my question lies in the physics or in the ...
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0answers
57 views
Resistor branding color. [closed]
If I have a resistor with 100 volts applied to it with a resistance of 100 $\Omega$, then the resistor would dissipate 100W. What is the color branding?
My first thought, following the table was, 1 ...
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3answers
2k views
Average power dissipated by a resistor on AC current
So let's say we have an AC current of 120 V at 60 Hz. Then i's waveform would be
$$f(t) = 120 \sqrt{2} \cos(2 \pi 60 t)$$ Or rather the amplitude times $\sqrt{2}$ times $\cos(2 \pi ...
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1answer
168 views
Which speed can an electric scooter reach on a given slope?
Electric scooters are always "given" as "working with slopes up to xx%", but what does it mean?
Given motor torque and power, scooter+driver weight and wheels diameter, how can I determine at which ...
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2answers
619 views
Does the 'mAh' rating of a battery have something to do with its power?
I'm curious about the 'mAh' of a battery: how can this impact the power of the battery?
I've done some research on the internet, and most of the articles I found explain about the 'amount of charge ...
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4answers
1k views
How does power consumption vary with the processor frequency in a typical computer?
I am looking for an estimate on the relationship between the rate of increase of power usage as the frequency of the processor is increased.
Any references to findings on this would be helpful.
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93 views
Energy efficiency Vs power efficiency
I want to understand if there can be any real difference between the requirement of Energy efficiency and the requirement of power efficiency for a physical system. For example for CMOS-based digital ...
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2answers
200 views
Should the term Watt's Law be used?
I'm revising some electrical curriculum for a technical training program. In the curriculum students have to calculate values using Ohm's law and the equation Power = Current * Voltage (or P = IV).
...
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1answer
108 views
Inefficiency Comparison of Car Air Conditioning vs. Open Windows
On a recent long, hot journey in Spain, I was pondering which was the most efficient way of cooling the car. Which of these would be the most effective?
Switching on the air conditioning, thereby ...
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3answers
185 views
How to imagine the following power and torque?
I can roughly feel a force of 10 newton only by considering the weight of 1 kilogram object.
How to imagine the following measurements?
Maximum horsepower 16 hp @ 9,500 RPM
Maximum torque ...
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2answers
153 views
Can wireless power transfer harm organic life by anyway?
Now, humanity can beam 50-60 watts power through 10 centimeter-thick concrete block. Can such wireless power transfer harm us by anyways?
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2answers
281 views
Lorentz engine to run a car?
Could a Lorentz engine (like the ones that move the write head inside of hardrives) be used to run car ? Would it be possable to get it producing 60hp, and a decent amount of tourque, if so how large ...
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1answer
92 views
Do you think it’s possible to make a power plant of the described kind?
We are working on a science project and try to engineer a power plant of a new kind. It is called Air HES (air hydroelectric station). The idea is described on our website.
Do you think it is ...
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2answers
296 views
Calculate power $P=V \times I$
I have an adapter which mentions like this...
Input: 100-240V~1.8A
50-60hZ
So how much power does it really consume?
I just knew ...
1
vote
1answer
453 views
How are the CPU power and temperature caculated/estimated?
From Wikipedia
The power consumed by a CPU, is approximately proportional to CPU
frequency, and to the square of the CPU voltage: $$
P = C V^2 f $$ (where C is capacitance, f is ...
3
votes
1answer
4k views
Is there any significance to 1.21 GW?
In connection with a related question on Science Fiction & Fantasy Stack Exchange page: does this number 1.21 GW make any sense? What is 1.21 GWatts? With what can you compare it? Can the ...
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1answer
67 views
is it possible to gain from charging cold battery
Is it possible to get higher load of energy into a battery if you charge it when its cold eg. +9C?
the battery is emptier, but does it let the power in?
Is it safe?
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2answers
306 views
How can you measure battery output to see if the wattage is accurate? [closed]
When you have a battery and it shows you the milliamperehours and volts. You can use those to calculate the wattage. How can you test the battery to see if its wattage is accurate or if the company ...
3
votes
1answer
118 views
What are some ways that humans could have influence over what sequence a star was in?
How would a society go about either preventing our sun in its primary sequence from going into a Red Giant a billion years from now? Or perhaps, accelerating the process of going from main sequence ...
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1answer
59 views
Boiling water reactor
What are the typical power densities in conventional boiling water nuclear reactor per cubic centimeter of fission material?
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1answer
451 views
Finding electric power generated using heat transfer
I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$.
Given:
$\alpha_s = 0.83$
...
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4answers
318 views
Should we forget fusion and focus on geothermal power? [closed]
Firstly I can say that I would love us to come up with a sustainable fusion solution. However with the latest estimates being 2050 at the earliest for an effective fusion solution and the planets ...
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1answer
30 views
Have Sterling Engines Been Used In Outer Space?
I was reading about Stirling Generators having potential applications for power generation in outer space. Have Stirling engines ever been sent into space?
