The time rate of change of energy
Questions tagged [power]
995 questions
2
votes
1 answer
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,…
Phil Frost
- 4,161
2
votes
1 answer
Why is the lamp with the lower power rating brighter in the series circuit?
If I have two lamps, both of them have different power values, and voltage value is constant , I've been told that the lamp that has less power would be brighter and make more light than the lamp that has a higher power rating in the series…
loody
- 23
1
vote
4 answers
Will Earth Hour do damage to power supply system?
There is always a debate around Earth Hour every year, and the opposite side of Earth Hour usually claims that
The (sudden) decrease and increase of the power usage in the start and end of Earth Hour will cause much more power loss (than the save…
user2503
1
vote
3 answers
Amplitude spectral density vs power spectral density
I'm reading the Wikipedia article on spectral density. It is said:
Sometimes one encounters an amplitude spectral density (ASD), which is the square root of the PSD; the ASD of a voltage signal has units of V Hz−1/2.[6] This is useful when the…
S. Rotos
- 903
1
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1 answer
Why are rotors like these on a cup anemometer not effective for wind turbines?
Intuitively, radial rotors (like these you would have on a wind speed meter) equipped with cups/cones/sails look like they should be very efficient at converting air flow into energy, given that they should "bite into" and trap the airflow giving it…
rackandboneman
- 121
- 5
1
vote
1 answer
How is it that a single transmission line can be modeled by a two port network?
I am studying electric power distribution. I've read in Kirtley's Electric Power Principles (2010) that a transmission line can be modeled by the 'pi' model. Which is a two port network with series conductance and parallel capacitance. But a…
JMcB
- 113
1
vote
0 answers
Building a CO2 laser power supply
So i bought a 15,000 volt franceformer for $160. This is used to power my CO2 laser that is also homemade. The power supply is the most expensive part by a landslide so I decided to ask around. I emailed the guy who built a laser like mine and he…
1
vote
1 answer
In 3 three power system, can damage occurs from incorrectly connected phases?
A three phase generator, no grid involved, phase 1 connected to phase 3 on the load, and phase connected to phase 1 on load, what is going to happen?
sdaffa23fdsf
- 113
1
vote
2 answers
Why Neutral and Ground Wire are Thin As Compare to 3-Phase Line Wire?
in 3-phase 4-wire systems line wires are big as compare to neutral wire.
as per law ,
so,area of neutral wire is low ,then resistance of neutral wire is high.
so, heat loss is more.
as per P=I^2R
so,my question is why we use thin wire for neutral.
1
vote
0 answers
Luminous intensity: from Volt to Candela/m2
I use a probe for converting optical power to an electrical current. I need to convert Volt to candela/m2.
The sensor, a photodiode, measure the brightness of the monitor leaning the probe on the glass (so there is not distance between the monitor…
RobertAalto
- 111
1
vote
2 answers
How to improve the power output of an AC motor without changing its characteristics
I have an AC motor at 230V/50Hz and 2.2 KW power that will power a drilling bit for cutting wood.
The motor has 3000 RPM, but if I attach the drilling bit (8 cm wide, 15 cm long and with a step of 8 mm) it just won't penetrate the log, so I'm…
Paul
- 121
- 4
1
vote
1 answer
Normalizing values in dB scale
I'm doing some experiments with optical power through a glass fiber. The power is measured in dBm. For the graphs that I make (Power in dBm vs time), I normalize the values relative to the initial power in dBm. But if I calculate the power to…
Gregory
- 33
0
votes
2 answers
Why is the relationship between power and amplitude squared?
I read on Wikipedia that "An example scale showing power ratios x, amplitude ratios √x" [1], i.e. that the relationship between power and amplitude is squared.
How come? Have this something to do with the relationship of power and electric…
warpi
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0
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3 answers
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 elements of the run.
Thank you for your answers but i…
panos
- 11
0
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1 answer
How deep would you have to put a steel pole to generate enough electricity to power one LED using geothermal energy?
I was thinking about how you might grow plants inside without sunlight powered only by LEDs. But to get the energy for the LEDs, one might drill a hole down into the Earth's magma and put a steel pole. Then the heat from the magma would heat up the…
user84158