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. C

    Instantaneous Power of Real Signals

    Homework Statement Hi, So I'm taking a communications module and we are being introduced to Energy Signals and Power Signals. Now in the notes, it starts off the chapter by saying "Suppose a signal x(t) is a real signal" and then it says The instantaneous power in x(t) is given by x^2(t)...
  2. N

    Power Ratings of RF Amplifiers

    Hi all I am studying RF amplifiers data sheets and there is some confusion i am facing in its specifications. One such amplifier claims Power Output at 50 ohm load with 20% duty cycle to be 2 KW. However, the minimum gain it specifies is 63 dB and maximum input it claims to be 10 dBm (around...
  3. JTC

    Windmills and Power Generation

    I tried yesterday with the gyro and did not make myself clear. So let me try with a windmill, please. I look at a windmill and I see the blades are spinning. Thus, the shaft axis has an angular velocity. I can ballpark and check the angular velocity with my eyes. I want a ballpark...
  4. JTC

    Gyroscopic Water Wave Energy Converters

    Say I have a disk spinning in a buoy. Let me say the spin axis is vertical to the flat surface of the buoy (or sea if there were no waves). Now along comes a wave (that will induce a "precession" of the disk/buoy. The axis of this precession is from "starboard to port." This would induce...
  5. CAT 2

    What is the correct equation to solve this power and voltage problem?

    Homework Statement A 4.0 Watt toy motor is connected to a secondary circuit of a transformer with 60 loops and a current of 0.10 A. The primary voltage is 120 V Homework Equations Vp / Vs = Ip / Is Ip = Pp / Vp[/B]The Attempt at a Solution 1. [/B]Vp / Vs = Ip / Is 120 V / 40...
  6. J

    Reactive power requirement requires which element

    Homework Statement Homework Equations I think it should be A for 1st and B for 2nd Shunt capacitor is used to improve power factor by giving reactive power to line. Series capacitor is used to improve efficiency of line as it nullifies effect of line inductance. And for 2nd Q proportional to...
  7. J

    Sequence Currents in a Power System

    Homework Statement It's a solved problem but I don't understand why is there no 30 degree lag from line voltage to lead voltage. Homework Equations Phase voltage = Line Voltage / 1.732 and there is 30 degree lag So shouldn't Ir be at angle 150 degrees.The Attempt at a Solution In Y line and...
  8. nmsurobert

    Power relation to lightbulb wattage

    Power is measured in watts and lightbulbs are rated in watts. P = W/t and W = Fd What is being displaced? electrical current?
  9. J

    Peak torque and power for an elevator motor

    Homework Statement A loaded elevator acge has a mass of 1500kg and a countermass of 1000kg. The cage is accelerated with 2m/s² to 1,4m/s and lifted to a height of 15m and stops at stand still. The inertia of the motor or the radius of the cablewheel is NOT given. The steady state speed of the...
  10. J

    Find the Capacitance when given the Power Factor

    Homework Statement w = 1 rad/s power factor is 0.8 lag Homework Equations Using Phasor we can do The Attempt at a Solution Since pf = 0.8 lag. I source lags V source by 36.87 degrees. Vc is voltage across Capacitor = Voltage across ( Resistor + inductor) Solving this I get C = 0.5 But book...
  11. V

    A Reducing computation for large power sets

    To illustrate my problem say I have the following table: Option, x , y A , 25 , 30 B , 5 , 12 C , 3 , 9 D, 12, 13 I want to create a graph of every possible combination in the set where the x values are added and the y values are added. For example say it was...
  12. N

    How many kg Uranium is needed for 5kW produced?

    Homework Statement Energy released is 5.6MeV, 5kW is produced, Half life = 87.7 years for Uranium Need to find how many kg you need to produced that much power. Homework Equations E = Pt, Q = (mass defect) * 931.5MeV/c^2 The Attempt at a Solution I solved for the energy released to be...
  13. CameronRose

    Reducing the power required to drive a slider crank

    Hi folks, I'm currently working on the design of a triplex plunger pump. I have conducted an investigation into the loading of the pump at maximum operating pressure using an analytical method (free body diagrams) and using rigid body dynamics to validate. In both analyses the pump has been...
  14. T

    Possible Line Power Conditioner hobby project

    Hi All, [This thread has been re-started to accommodate modification of the project for the benefit of anyone that isn't a qualified Professional. Specifically the use of a Low Voltage isolated Source.] I want to get the opinion of people with more experience than me, regarding a project I was...
  15. G

    AC synchronous motor power factor

    Is it true that AC synchronous motors (the ones with the DC slip rings and excitation current running into rotor poles) have a power factor of 1.0 when they run in synchronous mode? Would that be because with sufficient rotor DC current he rotating AC magnetic field is precisely counterbalanced...
  16. M

    MHB Approximation of eigenvalue with power method

    Hey! :o We have \begin{equation*}A:=\begin{pmatrix}-5.7 & -61.1 & -32.9 \\ 0.8 & 11.9 & 7.1 \\ -1.1 & -11.8 & -7.2\end{pmatrix} \ \text{ and } \ z^{(0)}:=\begin{pmatrix}1\\ 1 \\ 1\end{pmatrix}\end{equation*} I want to approximate the biggest (in absolute value) eigenvalue of $A$ with the...
  17. G

    What is the relation of mass and power?

    How should power be calculated in a situation where distance and time are both given, as well as mass. At first, I was thinking of just using W=Fx (force as mass x 9.8) to solve for work, and then I would take the solution for work and put it into P=wt. Does this make sense? That's my best...
  18. JTC

    Calculating power from a prescribed rotation

    Hi, Forgive me for this trivial question. I am confused. Let's say I have a gyroscopic device in which the rotor is set to spin at a prescribed angular velocity. Next, put it on an ocean surface in which the ocean waves induce a precession. These two rotations, then induce a moment (induce a...
  19. J

    Maximum power is transferred when load R = Source R ?

    Homework Statement Maximum power is transferred to variable load when: 1) RL = Rs 2) RL not equal to 0. and Rs = 0 3) RL = 0 and Rs not equal to 0 4) RL = Rs/2 Homework Equations Maximum power theorem RL = Rs The Attempt at a Solution But if Rs = 0, then current is maximum, so load get...
  20. Delta Force

    Power Production at Hanford N-Reactor

    During the early development of nuclear power many utilities were concerned that the United States federal government would create an "Atomic TVA" and crowd them out. As a result the plutonium production reactors in the United States didn't have steam turbines to generate electricity from the...
  21. D

    Magnetic fields outside a shielded power cable

    I was recently having a discussion about magnetic fields outside of a shielded power cable. My understanding up to this point was shielded cables only shields electric fields and not magnetic fields which are associated with current flow inside a cable. For the shielding to shield magnetic...
  22. J

    Condition for parallel AC Mains power transformer operation

    Homework Statement Homework Equations I think both A and C are right answers. The Attempt at a Solution 1 condition is pu Z(leakage) must be same on respective KVA rating for load sharing. Now: Zpu = Z(actual)/Z(base) ----equation 1 For Zpu of both transformers to be same, the right side...
  23. CPHY

    Questions about Energy (Work and Power)

    My class just started the Energy unit and I would like to make sure my answers are correct to our HW questions. I am in high school Physics. Thanks. 1. Homework Statement A student lifts their 100N book-bag 1meter in order to put it on. How much work did the student do in lifting the book-bag...
  24. S

    How Do You Calculate Power in These Physics Problems?

    Homework Statement There are three problems: 1. How much power is required to lift a 10.00 kg barbell at a speed of 3.0 m/s? 2.What is the average power supplied by a 70.0 kg firefighter climbing up a ladder in 10.0 s? 3. A man pulls a wagon with a force directed 22.0˚ above the horizontal...
  25. N

    Power Series Equation for Amplifier and Harmonics

    Hi, I keep reading in multiple sources that amplifier output can be given by Vout = a0 + a1v(t) + a2v2(t) + a3v3(t) + ... + anvn(t) I've checked in three of my textbooks and there is not a clear definition (its often just stated) why this equation is used and why it works. I am not looking...
  26. billyray

    Solve 3 Phase Total Power Problems

    Homework Statement I have included the problems attached below. I have looked at a recent post and the equations made sense to me but I am very new to 3 phase systems basically know only what I have learned from trying to answer my questions. i feel my attempt is wrong from what I have seen...
  27. jonnybmac

    What is the relationship between engine power, force, and speed?

    Homework Statement I am having difficulty understanding the conversion between power and rotation at the engine and at the wheel. Can you please state which parts are right and wrong, and why please as I think I've spent that long on researching I've confused myself with too much information...
  28. Pushoam

    Power needed to keep conveyor belt running

    Homework Statement Homework EquationsThe Attempt at a Solution Taking change in the kinetic energy per unit time as power, P = ## \frac {d W}{dt} = \frac {d K}{dt} = \frac 1 2 \frac { dm} {dt} v^2 = 36.75 ## watt...(1) ## P = \vec F \cdot \vec v = \frac{ dm} {dt} \vec v \cdot \vec v =...
  29. J

    Help interpreting a design for power management unit

    Hello, I have been looking to build a pmu similar to this device, it will be for domestic use. https://www.digikey.com/en/articles/techzone/2014/jan/low-cost-microcontroller-based-phasor-measurement-units-improve-smart-grid-reliability I am having a bit of trouble with the sampling part and...
  30. J

    Power Electronics: Choppers RLE Load

    Homework Statement Homework Equations I rms for triangular waveform = I(max)/ (1.732) R = V/I The Attempt at a Solution Since there is RLE load, current waveform is triangular. It is Source current is Average of I source. I used integration. Assumed Time period = 10 seconds. So T on = 5...
  31. J

    Power Electronics controlled rectifier solved example

    Homework Statement Homework Equations Solved example The Attempt at a Solution I think the red part should be (alpha/firing angle) = 180 - 45 Here since the angle is 45, it makes no difference if you do 90 + 45 or 180 - 45, but i think it should be 180 - 45. Am I right?
  32. J

    Power Electronics Rectifier Firing Angle and Overlap Angle

    Homework Statement Homework Equations Since question says the current is always continous, so overlap is always there. So option B is incorrect. Also since firing angle is increased from 0 to 45, the overlap angle will reduce. So it'll be less than 45. So option A is incorrect. The Attempt...
  33. J

    Load Flow Order of Jacobian Matrix Power System

    I'm studying Newton Raphson Method in Load Flow Studies. Book has defined Jacobian Matrix and it's order as: N + Np - 1 N = Total Number of Buses Np = Number of P-Q Buses But in solved example they've used some other formula. I'm not sure if it's right. Shouldn't order be: N + Np - 1 N = 40 Np...
  34. Y

    Automotive What limits the max power rating of a V-Belt drive?

    We know that belt drives are limited in their max possible power rating and most high power/torque applications(trucks) use gear drives. I wanted to know the main factor that limits the power/torque rating of belts. Is it Frictional slip or Belt material? If the frictional slip could be...
  35. J

    Power System Fault Phasor Diagram

    Homework Statement Homework Equations If load is inductive current lags voltage. If load is capacitive voltage lags current The Attempt at a Solution Current lags voltage since wire is inductive. So IF1 lags VF1 and IF2 lags VF2 But book says answer is C Why should VF1 lag IF1? This will...
  36. T

    Why we say that electrical energy is power over time p x t

    Greeting . how electrical energy can be power over time when electrical energy is actually potential energy . from a lot of sources (wiki ,study.com..) comes the information that electric energy is potential or kinetic energy in other sources is said to be electric power p x t so i am...
  37. J

    What does ZPB mean in power systems?

    Hi, So my power system book has a diagram for zero sequence impedance. I cannot find the full form of ZPB. I googled it up but couldn't come across anything.
  38. G

    Power given to particle by centripetal forces

    Homework Statement A particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration a varies with time t as a = k2rt2, where k is a constant. Show that the power delivered to the particle by the forces acting on it is mk4r2t5/3. [/B] I have solved...
  39. A

    The Power Needed to Accelerate

    Homework Statement Hi, guys. I'm in a bit of a quandary. I'm trying to calculate the power a motor should have in order to move a mass a certain distance. My calculation keeps telling me that the horsepower output is much lower than my reference scenario. Here's the situation. I'm trying to...
  40. Pushoam

    Calculating Power Output of a p-V Engine

    Homework Statement Homework EquationsThe Attempt at a Solution P = 1500 * [area occupied by the cycle = ## 4 p_0 V_0 ## ] /60 = 15 kW Is this correct?
  41. Domenicus

    How to project a high power white line

    Hi I have a personal art project and I am stuck, because of very limited knowledge. I'd like to project an 1-2 meter white line from 1-3 meter distance. The projected line should be as thin as possible (3-10mm) and as powerful as possible. I created a DIY projector, but my problem is that, the...
  42. N

    My Plug And Play Solar Energy System

    Hi everyone, i'd like to share my packaged (plug and play) solar system project that I assembled at home. I used mostly standard parts such as a charge controller, inverter, 12 Volt UPS battery, and a pair of NEMA 5-15 R power outlets. I built the automatic transfer switch and battery...
  43. PSuran

    Why Does Doubling Speakers Double Sound Pressure with Less Power?

    Hello, I have a question that I've been struggling to find an answer to / understand. Probably because my understanding of physics is quite limited :) Before I ask the question, these are the things I take as facts, so please correct me if something is wrong: 1. A speaker in half space...
  44. S

    Engine flow rate with varying power settings

    Most engine specifications I have found only provide the engine mass flow rate for take-off setting. For example, the V2500 has a mass flow rate of 354.25 kg/s. How does the flow rate vary through different power settings? For example, if the engine is on idle, will the mass flow rate be 0...
  45. C

    Which Type of Geothermal Power System is the Best?

    There are three geothermal systems that are commonly used: sry steam, flash steam, and binary cycle https://www.eia.gov/energyexplained/index.cfm?page=geothermal_power_plants . What are the efficiencies of the plants from best to least effecient on average?
  46. J

    Power dissipated across a transistor regulator

    Homework Statement [/B]Homework Equations For the 1st part Ohms law and resistance across zener is 10V[/B] I can't get 2nd The Attempt at a Solution For 1st part I took Vi/p = 18V[/B] Putting KVL for left loop of source-->collector-->base-->zener-->ground 18 = Vcb + 10 So Vcb = 8V And Vbe =...
  47. Cocoleia

    Why does a larger synchronous generator have a better rating

    Homework Statement I read in my notes that "The physical size of a synchronous generator of a particular rating is larger than one of a lower rating" Why is this so ? The Attempt at a Solution Is it because a larger one would be able to supply more power and therefore the rating would be higher ?
  48. D

    EM Wave Propagation Homework.Incident/Transmitted Power Density

    Homework Statement An E field with f = 2.45*10^9 Hz passes through a material with the following properties e_r = 10 u_r = 1 sigma = 1 (S/m) The Incident E field has peak magnitude of 300 V/m at the air to surface boundary. (a) *solved* Find the incident power density at the material...
  49. N

    US solar power generation for 2014-16

    Solar generation results for US are out for 2016. Year over year: http://www.eia.gov/electricity/annual/html/epa_01_02.html US: Net Generation (Thousand Megawatthours) 2014 Solar: 17691 (that's 0.43%) All sources: 4093606 https://www.eia.gov/electricity/annual/pdf/epa.pdf: US: Net Generation...
  50. ferrariistheking

    Work, energy, power unit (coulombs)

    Homework Statement For a positively-charged particle at the origin, and a negatively-charged particle lying to its right on the positive x-axis, the electrostatic force on the negative charge is attractive, and Coulomb's Law gives the magnitude of that force: F = k |Q1| |Q2| / x^2 k is...
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