The time rate of change of energy
Questions tagged [power]
1024 questions
121
votes
12 answers
Why don't we use weights to store energy?
One of the main reasons why we haven't switched to clean energy is the lack of efficient storage methods - But, why aren't we using dead weights to store energy and draw it back later when needed? As an example of what I mean:
Blake Angelo
- 1,181
84
votes
6 answers
Why does public mains power use 50-60 Hz and 100-240 V?
Is there a physical reason behind the frequency and voltage in the mains electricity? I do not want to know why exactly a certain value was chosen; I am rather interested to know why that range/order of magnitude was selected. I.e., why 50 Hz and…
SuperCiocia
- 25,602
56
votes
10 answers
What practical issues remain for the adoption of Thorium reactors?
From what I've read on thorium reactors, there's enormous benefit to them. Their fuel is abundant enough to power human civilization for centuries, their fission products are relatively short-lived, they're far less prone to catastrophic failure,…
GordonM
- 995
31
votes
5 answers
Is it possible to build a thermoelectric nuclear power plant?
Current nuclear power plants are essentially an enhanced version of a kettle, which seems like a stupidity caused by a lack of other options. We heat the water which turns to steam which rotates the turbine, which is total waste of energy due to the…
hijarian
- 515
30
votes
4 answers
How big is a 1kW fire?
What is the size/scale of a wood fire that is producing 1kW?
I'd like to improve my ability to conceptualize various power scales.
Dave
- 4,203
29
votes
6 answers
Can a gym be built to supply electricity to homes?
A moving magnet induces a current in a conductor, then shouldn't we be able to generate electricity through manual labour?
I was thinking about building a gym that used magnets as weights. People would lift the magnets up and down creating a change…
masterwarrior123
- 1,323
- 1
- 12
- 20
28
votes
5 answers
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.
Lazer
- 846
24
votes
3 answers
Is there a theoretical lower limit to watts needed for lumens?
For example 100 watt incandescent bulb produces 1600 lumens.
Led 23 watt can produce 1600 lumens.
Is there minimum amount of watts needed ?
steviekm3
- 349
21
votes
8 answers
Why do we reduce only current to prevent power loss? Why not voltage?
In power transmission lines current is kept low and voltage is kept high to reduce the power loss. This is because $P = I^{2}R$ and $P = VI$. In order to reduce power loss we have to reduce $I$ since $P = I^{2}R$ ($R$ is obviously a constant). And…
Plan'k-44
- 335
21
votes
9 answers
The water analogy seems to imply that power = current. Why is this incorrect?
Many people think of the water analogy to try to explain how electromagnetic energy is delivered to a device in a circuit. Using that analogy, in a DC circuit, one could imagine the power-consuming device is like a water wheel being pushed by the…
lyndon
- 379
20
votes
7 answers
Why is it impossible for the reactor of the nuclear power plant to turn into an explosive nuclear bomb?
Is it true that both work on the same principle of operation: the interactive fission chain reaction 235U/239Pu and the bombardment of uranium-235 by fast neutrons produce a fission chain reaction accompanied by an enormous thermal energy in…
user336488
16
votes
11 answers
Are energy and work the same thing?
When revising formulas the other day I came across something:
Energy = power × time
If we substitute power we get
Energy = work/time × time
The time cancels out. So is work equal to energy?
Slow learner
- 195
15
votes
6 answers
How do you determine power flow direction in a transmission line?
Below is a picture of a typical transmission line(about 200 kV). Is there a simple physics experiment which can be performed safely near the line, to determine the power flow direction. Or in other words: where is the generator and where a…
Martin Gales
- 2,727
14
votes
8 answers
Understanding voltage and power in the fluid analogy for DC circuits
I am trying to understand electric circuits (ie voltage, current, power, and resistance). For the most part, everything makes perfect sense, but for some reason I do not feel as if I understand the proper definition of power. Yes, I understand the…
4Matt
- 285
14
votes
5 answers
$\rm Lux$ and $W/m^2$ relationship?
I am reading a bit about solar energy, and for my own curiosity, I would really like to know the insolation on my balcony. That could tell me how much a solar panel could produce.
Now, I don't have any equipment, but I do have a smartphone, and an…
Mads Skjern
- 275