What is Power: Definition and 999 Discussions

A power outage (also called a power cut, a power out, a power blackout, a power failure, a power loss, or a blackout) is the loss of the electrical power network supply to an end user.There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, cascading failure, fuse or circuit breaker operation.
Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as hospitals, sewage treatment plants, and mines will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other critical systems, such as telecommunication, are also required to have emergency power. The battery room of a telephone exchange usually has arrays of lead–acid batteries for backup and also a socket for connecting a generator during extended periods of outage.

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  1. A

    Effects of brownouts and power spikes on linear power supplies

    What are the effects of brownouts and power spikes on linear power supplies in particular; e.g., a linear power supply that provides 24 V to an inductive angle encoder? Thanks for any information you could provide.
  2. amazingjoe

    Could you use Solar to power a DC to AC Inverter? (Description below)

    I'd like to take Solar Panel power output and use it to power an AC outlet on the ultra-cheap. I know a lot of people use Solar to connect to a purpose built inverter and also have a battery somewhere in the mix to provide a stable output but wondering if the following (using the assumptions...
  3. T

    I Voyager Spacecraft beginning to Power Down

    An interesting article on some of the history of, and discoveries by, the 44+ year old Voyager spacecraft s. The bean counters originally planned a 4 year mission for Voyagers 1&2. However, the scientists and engineers involved saw a golden opportunity that wouldn't repeat for another 176...
  4. C

    I Acceleration as a Function of Time Using Constant Power

    Hello everyone! I was doing some dimensional analysis to find an equation that gives a acceleration as a function of time, using constant power. I came up with the equation $$a = k\sqrt {\frac P {mt}}$$ I differentiated velocity with respect to time in order to check my work and also checked out...
  5. J

    Misc. Help with power wheelchair modifications

    I have a jazzy pride 1121 power wheelchair that I need help with. I have installed larger tires so I wasn't limited to where I could take it in my yard. Because of the increased size of the wheels, it now lacks the power to climb inclines. I was told that possibly a more powerful controller...
  6. SuperPat

    B How to Calculate Power and Torque for a 15kg Load at 15 RPM?

    Hi all I am Belgian and I have difficulty with english formulas. I'm trying to calculate the power and torque required of a motor to rotate a load. Here is the problem: I have a motor (axis up) on which is fixed a cylindrical load of 15Kg. The diameter of this load is 400mm Calculate the power...
  7. anorlunda

    The Grim Power Outlook Spreads Beyond Texas

    This year, the grim outlook goes to other parts of the USA. Not just Texas. NERC is the most credible source we have for US electric reliability topics.
  8. samy4408

    I Question about X-ray power emitted by the Coolidge tube

    hello i found this equation in a course about x rays , and i couldn't find it anywhere else they said that it is the theoretical expression of the energy spectrum , and dφ/dE is variation of the power emitted by the Coolidge tube as a function of the energy of the x ray. but i didn't understand...
  9. T

    Calculating Force on Shaft Bearings - Hydro Power Systems

    I know the moment of inertia and the rotating speed of a shaft, and the allowable vibration is 2mm/sec. How is the force calculated? What is the formula to calculate the force on the shaft bearings which are a know distance from centre of gravity? Thanks
  10. A

    What is the Power Loss in a Transformer?

    ##\frac{N_S}{N_P} = \frac{240}{12\times 10^3} = \frac{1}{50}## ##I_S = \frac{N_P}{N_S}I_P = \frac{N_P}{N_S}I_P = 50\times 2 = 100## Amps ##P_{loss} = I_S^2R##, but I don't know how to find R
  11. T

    Optical power of Smartphone (Galaxy S20) torch

    In doing a project on phototransistors I am using my smartphone as illumination source. In order to find the responsivity of the induced current from the light, I need to know the surface power density, which I could estimate, if I knew the effective optical power of the light from the...
  12. leifh

    Question about electrical power compared to mechanical power

    I am new here and I am seeking for help:) Thank you so much. In engineering, electrical formula often analogy to mechanical formula. eg. power[W] = pressure x volume flow rate vs power[W] = voltage x current My question is could we make the simplest unit between electrical and mechanical...
  13. A

    Adjusting the Power Factor of an RLC circuit

    a) An inductor should be added because that would cancel out the lag of the voltage with the current so that P = IV is at a maximum since V is ahead of I in an inductor b) ##cos(\phi) = \frac{R}{Z}##, ##R = Zcos(\phi) = 60\times 0.5 = 30 ohms## ##X_l - X_c = \sqrt{Z^2 - R^2} = \sqrt{60^2 -...
  14. P

    Parallel RLC Admittance, Current and Power Vector Diagrams

    (An even longer-winded version was written and deleted out of mercy.) Assume an AC voltage at zero degrees applied to an ideal parallel RLC circuit. For a predominantly inductive circuit, the vector diagram for current should show the supply current in the fourth quadrant (i.e. with lagging...
  15. Algr

    Why does demand knock power plants offline?

    https://www.cnn.com/2022/05/14/us/texas-heat-wave-ercot-conserve/index.html Why would they make plants like this? If demand gets too high, the plant just stops? And potentially knocks out other plants? Wouldn't it make more sense to cut off a few places at a time so that the plant can...
  16. gremory

    A Power series in quantum mechanics

    Just earlier today i was practicing solving some ODEs with the power series method and when i did it to the infinite square well i noticed that my final answer for ##\psi(x)## wouldn't give me the quantised energies. My solution was $$\psi(x) = \sum^{\infty}_{n=0} k^{2n}(\cos(x) + \sin(x))$$...
  17. Melbourne Guy

    Our space ship has lost power, what happens now....

    I'm about 25,000 words into my latest novel and the story arc is coming together nicely, but one aspect I need thoughts on please is what would happen inside a spaceship that has been grievously damaged in battle to the point that it has been abandoned by the fleet as a 500m long wreck...
  18. PhysicsTest

    Negative Power Supply Clarification

    I am confused with the negative voltage supply connections in electric circuit. If i have circuit as below with -5V source it is same as below In the 2nd circuit the 5V is directly shorted with the ground, does it mean the circuit is not correct? Am i missing something? Please advise.
  19. F

    Engineering Power Flows and Losses in a line between two buses

    Question: Equations: My solution: Could someone verify my answer?
  20. A

    Voltage Drop in Parallel Receptacle Wiring

    I know how to solve the question but I am a bit confused about why there is a current of 3 A and a voltage of 110 V requirement for the refrigerator but the power plant only supplies 110 V. How can there be a voltage drop on the refrigerator load of 110 V, when there is also a voltage drop on...
  21. C

    Radio Power Conversion: Convert mV/m or nW/m2 to Watts

    I have searched the internet and spoken to the manufacturer of my equipment and can not find an answer. I am using RFExplorer (test equipment) to measure the power generated by my ham radio antenna. The only options for displayed power is mV/m or nW/m2. I am trying to find out how to convert...
  22. fsonnichsen

    I Calculating Candela Power for LED

    I am looking for the power in watts, total, put out by and LED. This for example, if I enclosed the complete device in an integrating sphere, what power output would be measured in watts. Unfortunately a lot of the vendors report power in Candela. I could not get a response on this, but I am now...
  23. bluesteels

    AC circuit power formula question

    im kinda confused on why can't you just use the formula P=I^2R. Can you just use Vrms or Vamp (not sure which one is it) and the value of R which is 105Ω to solve for I Then just plug it in the formula P=I^2R. But when i did that it the wrong answer so is this formula don't work for AC...
  24. C

    Power required to climb a 20-m-tall building in 55s

    Summary:: A 90 kg firefighter needs to climb the stairs of a 20-m-tall building while carrying 40kg of gear. How much power does he need to reach the top of the building in 55s. So first the total mass of our system is 130 kg. Using this mass, I found the potential energy the firefighter would...
  25. A

    I Power equation in railgun operation

    In a capacitor discharge through a plain resistor, the capacitor power supplied at any instant is VI; the power dissipated in the resistor is I²R. So VI = I²R. Consider a railgun operated with a capacitor bank. At any instant of capacitor discharge, the power supplied is VI. The total power...
  26. A

    Audio/Video Please help, require schematic diagram of power amplifier ROYAL L1200

    Hi to all much appreciation for you all,please is there anyone who can help me the schematic diagram of power amplifier ROYAL L1200
  27. F

    Engineering Find the reactive power before power factor correction

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  28. Joshy

    Engineering Source impedance using given voltage swing and power

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  29. Kamuna

    Engineering Understanding Rankine Cycle Pressures: Should P2 Equal P3?

    Is this the right path in solving this problem? Am i finding the correct enthalpies? I am also having difficulty understanding so what I've understood is that in a rankine cycle P2=P3 but here P2 is given and P3 has a given variable which is T=25 C too so should I neglect P2=P3? Heres my...
  30. G

    I Interpreting Thermal Power in Cylinder with Source & Sink

    I have a cylinder that is separated with an insulator. In the internal cylinder there is a thermal source, while outside the insulator we have a thermal sink. The power of the internal cylinder is positive, while of the external one in total is negative. How I should interpet the results. Like...
  31. A

    Engineering How to calculate the power distribution through this gearbox?

    Greeting! My problem is to understand the flux of power inside this gearbox for example I can´t understand why the power in load 2 and load 1 are not equal to the power of the motor (suppose 100% efficiency). if this gearbox was an energy circuit (how to know that the energy is transmitted and...
  32. A

    Chernobyl loses power, spent fuel storage question #Ukraine

    So the news are in that for whatever reason the electricity to the plant has been shut down. Now given the reactor have been long stopped there is no danger I would assume to the plant as such but the question is about the spent fuel assemblies that are still on site...
  33. bluesteels

    Power formula for circuit when another resistor is added in

    On Chegg they solve for V using P=V^2/R using 36W and R1= 25Ω, which is equal to 30V then they add R1+R2 = 40Ω and they plug in P=V^2/R and solve for P which is 22.5W I'm confused on why they didn't use P=I^2*R cause you know the system is in series so I is the same and solve for I then...
  34. kingofjong

    I Maximizing Compound Bow Power: The Role of Longer Limbs Explained

    Hello If a compound bow has longer limbs will it have more power? Longer limbs means more limbs, hence more tension is building when limbs bend. That tension transfers to the bow string. Is this a true statement. I know there are other factors for making a powerful compound bow. Is long limbs...
  35. amgc63

    Why Is Y Considered 1 in Antenna Power Gain Calculations?

    Question; Given that a dipole antenna has directional gain of 2, calculate the power gain in Dbi? Answer; Power gain = 10 log (x/y), where y =1 Power gain = 10 log (2/1) = 3dbi My question is….how come y = 1?? Thanks in advance
  36. Greg Bernhardt

    Ukraine nuclear power plant Zaporizhzhia on fire

    Let's keep this non-political, similar to the Fukushima thread. Thanks! https://finance.yahoo.com/news/1-ukraine-nuclear-power-plant-001225198.html
  37. anorlunda

    UK Power Refunds: Halifax & Newcastle Postcodes Receive 13-Figure Sums

    I would like to share this, just because it is so funny. https://www.bbc.com/news/uk-england-tyne-60369098 If any PF members got this refund in the mail, please let us know.
  38. H

    Finding 2 solutions of this Bessel's function using a power series

    I have to find 2 solutions of this Bessel's function using a power series. ##x^2 d^2y/dx^2 + x dy/dx+ (x^2 -9/4)y = 0## I'm using Frobenius method. What I did so far I put the function in the standard form and we have a singularity at x=0. Then using ##y(x) = (x-x_0)^p \sum(a_n)(x-x_0)^n##...
  39. B

    A Power induced shift in rotational transitions for a diatomic molecule

    Hello! I am analyzing some data from some rotational transitions between 2 electronic energy levels in a diatomic molecule. I noticed that for different runs that covered the same regions, the peaks we observe are shifted with respect to each other when the power of the laser driving the...
  40. SherLOCKed

    How is the Power Spectrum of Matter Density Field Defined?

    The definition of power spectrum of matter density field is given by eq(1). I have also seen definitions of power spectra given by eq(2) . Does this mean (2\pi^3) has been absorbed in the correlation function? $$P_{xx}(k)=(2\pi^3)\delta(k-k^\prime)<x(k)x(k^\prime)>$$ .. (1)...
  41. Cosmology2015

    Tension at a SPD for Solar Power System

    Hello there! I am using a Surge Protection Device (SPD) for Solar Power System. My home uses a 3-phase system (380V and 220V at each phase). What should be the tension between the phase and ground at the SPD? And between the ground and neutral? Should be any tension at all? God bless all. PS. My...
  42. S

    Engineering How am I susposed to find the active power here?

    Hi everybody; With a halogen transformer with the data U = 230 V, f = 50 Hz, I = 1.5 A and cos ϕ = 0.35 a reactive power compensation can be carried out with a parallel capacitor Cp. ¨ (a) Calculate the value of Cp to achieve a power factor cos ϕk = 0.9. I did that like this; First I...
  43. bob012345

    B Thermodynamics of Resistive Heating at Low Power

    Summary:: This is a question about resistive heating at low power in a thermally sealed chamber. Suppose one has a resistive wire inside a small very well insulated chamber that can stand very high temperatures such as 1500C. For applications such as a kiln, the heating element is powered at...
  44. P

    Find the total power developed in the circuit given the readout

    Here is the problem with my power calculations in blue. My reasoning is that + terminal is higher potential, − terminal is lower potential and if the reference goes in the direction of decreasing potential then p=vi and if it goes against the decreasing potential then p=−vi. I've applied this...
  45. S

    Can power supplies/adapters be used to clean up dirty generator power?

    I have a portable generator that I use for backup power at my home in case of a loss of power. I understand that the power from these generators is not clean because both the voltage and frequency are not very stable and this is bad for sensitive electronics and may even damage them. I am...
  46. Borek

    Power surge video - why does the spark travel?

    Any idea what is the physics behind? Why does the spark travel down the line?
  47. C

    Lifting power at the bottom of the ocean?

    Hello, I'm a little confused about water pressure at extreme depths. Let's say that you attached a 100 lb. weight to a barrel, and the barrel had barely enough buoyancy to be able to just hold that weight at the surface (see Figure 1.) Then, you took the same barrel and you put it at the...
  48. L

    Intensity of a laser beam at a certain distance

    I haven't been able to pinpoint a definition of "angular divergence" of a laser so by pure intuition I assumed it would be something like ##\theta=\frac{2R}{D}## and with that I have that the radius of the lase beam is ##R=\frac{D\theta}{2}=90\cdot 5 \cdot 10^{-6} m=450\ \mu m## so...
  49. warhammer

    Question on Resolving Power of Diffraction Grating

    I have doubts about my work for the second part of the question, where I am asked if resolution will be possible or not. For the first part, I calculated No. of lines N=6.43*10^2 lines/cm For the second part, I have attached below a snapshot of my neatly written work. I request a PF member to...
  50. alan123hk

    B Measuring Light's Brightness & Power Flux Relative to Observer's Speed

    Assuming that the observer moves along the direction of the light, does the speed of the observer's measuring instrument relative to the light source (which may be close to the speed of light) affect the brightness and/or power flux density measured by the observer? I'm not sure about this...
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