Power Definition and 999 Threads

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. S

    Electric motor: power and RPMs

    I am helping a friend with a project, and am wondering if this statement is true. "To double the RPMs of a central drive shaft motor, you must quadruple the input." In other words, if an electric motor being supplied with 1 Watt spins at 500 RPMs, one would need 4 watts to spin at 1,000 RPMs...
  2. MikeTownsend

    DC motor voltage recommendations for a bike and power tools

    I have been working on some projects, I build a glass grinder, faceter with a 120v induction AC motor. Its not possible to effectively change the speeds with electronic controls being a single phase motor. It is using belts and pulleys for now. So I am wanting to build several tools, rock...
  3. S

    A Calculating the power spectra of scalar perturbation

    I'd like to numerically calculate the power spectra of the scalar perturbation at the Hubble crossing in warm inflation, my problem is that I don't know how to do it. As I know, the Hubble crossing happens at the onset of warm inflation where the different modes become larger than the Hubble...
  4. Henry Rufin

    Why does the power consumption of a plucker machine vary with rotational speed?

    hi, i have a study on a plucker machine and it came out that when the rotational speed of the plate is low, the power consumption rate is high and if the rotational speed is high, the pcr is low. what is the possible explanation for that? thanks in advace.
  5. EnumaElish

    What is the fixed cost vs. variable cost breakdown for a nuclear power plant?

    I am trying to understand the fixed cost of a nuclear power plant relative to variable cost. By fixed cost I mean "cost that does not vary with the amount of the power outputted over a given time period." By variable cost I mean "cost items that vary with the amount of the power outputted...
  6. J

    Directly power house with alternator

    My plan is to reduce electricity use supplied by the grid by having a waterwheel partially power a house. From my simple research I've learned that hooking an alternator up to the waterwheel would work. Since a house runs on 120V AC and an alternator produces (correct me if I'm wrong) 13.8 -...
  7. K

    Help with torque and power required please

    I am looking to build a skateborad like device that i want to power with electric skateboard-like system. However I only want it to go 1.1m/s using 60mm wheels moving a 100kg load for 12 km. I am looking for help determining gear sizes, motor sizes and specs, really anything. I have seen so...
  8. Ab Zar

    Please help to find the power supplied by the 4-A

    Homework Statement i solved 9 times all not correct please share with me what's wrong Homework EquationsThe Attempt at a Solution
  9. O

    Can Power Lines Transmit Radio Signals in Emergencies?

    Our street electric power lines have frequency of 50 Hz or 60 Hz.. what would happen if you increase the frequency higher to radio frequencies or microwaves.. would current still flow? and can you make it as antenna for emergency transmission?
  10. AishaGirl

    B Time Dilation Equation: Why is it to the Power -1/2? | AQA Exam Board

    Hello, AQA is a British exam board and on their paper they have a list of equations. Can someone tell me why the time dilation equation is to the power -1/2? Thanks.
  11. K

    Why won't power utility company charge for kVA instead of kW

    Hello all, As I understand (and realize when looking at my electricity bill) it seems all power utility company (in residential market) only charge for kW not kVA. But somehow I find it a bit weird when I think about it more deeply. Wouldn't it make more sense to charge for kVA ? Otherwise, it...
  12. C

    Alternate Heat Expansion Media for Nuclear Power Plants

    I am interested in whether it might be possible to select a more efficient heat expansion media for nuclear power plants than water, which has a very specific heat and a very high heat of vaporization. The high value of the specific heat and the heat of vaporization of water requires much...
  13. G

    Calculating Flow from Tank to Vessel w/ Power

    I am trying to calculate the flow in a system from an underground tank up through a pump into a vessel. But cannot find or derive a formula that yields a good result, I don't think I can use the same head calculations as Velocity will have changed. 1. Homework Statement ρ = 1000 kg m–3 μ =...
  14. A

    Help to understand the concept of Power

    Power is described as the Velocity at which Force is applied to an object (P=F*d/t) However, how are the Force and Velocity independent? Doesn't the Force applied affect the Velocity of the object? For example, let's say you want to lift a 19.62N (2kg*9.81m/s^2) object upwards 1 meter in 1...
  15. PhysicsCollegeGirl

    Master Power Series Convergence with Expert Help - Examples Included

    Homework Statement [/B] There are three problems that I am struggling with. 1. ∑[k2(x-2)k]/[3k] 2. ∑[(x-4)n]/[(n)(-9)n] 3. ∑[2k(x-3)k]/[k(k+1)] The Attempt at a Solution On the first two I am having problems finding the end-points of the interval of convergence. I use the ratio test. 1...
  16. G

    Using Bernoulli's Equation to find Power Requirement

    Homework Statement Calculate head required for the pump and then its power requirement assuming 70% efficiency. The lower storage vessel is vented to atmosphere (assume 1 bar pressure) . I have the following given information: Pipe Area = 0.00636m^3. Flow(Q)= 0.01m^3/s Average Velocity =...
  17. B

    Calculating Power & Torque for Flywheel Drives

    Hi I have a personal project, In link bellow in figure A I need to calculate appropriate power motor (HP) and torque (N.M) to drive flywheel at maximum speed 2000 rpm and what is value of resulting power on 750 rpm pulley. In figure B if we use two flywheel the weight for each half weight of...
  18. P

    Each day a quality engineer selects a random sample of 60 power supplies

    Homework Statement Each day a quality engineer selects a random sample of 60 power supplies from the day's production, measures their output voltages, and computes a 90% confidence interval for the mean output voltage of all the power supplies manufactured that day. What is the probability...
  19. Eclair_de_XII

    Finding a power series solution to a differential equation?

    Homework Statement "Find the recurrence relation in the power series solution for ##y''-xy'-y=0## centered about ##x_0=1##." Homework Equations ##y=\sum_{n=0}^\infty a_nx^n## Answer as given in book: ##(n+2)a_{n+2}-a_{n+1}-a_n=0## The Attempt at a Solution ##y=\sum_{n=0}^\infty a_n(x-1)^n##...
  20. A

    What Is the Smallest Spot Diameter the Human Eye Can Detect?

    Homework Statement The resolution of the eye is ultimately limited by the pupil diameter. What is the smallest diameter spot the eye can produce on the retina if the pupil diameter is 2.59 mm? Assume light with a wavelength of λ = 550 nm. (Note: The distance from the pupil to the retina is 25.4...
  21. Arman777

    MATLAB Matlab Power Fit on Graph-Codes

    I have some data and I need power fit.And display it on the graph.But I couldn't find the right codes for it.(I need codes) Here my graph, Here my codes, >> x=BN(:,2); >> B=BN(:,1); >> plot(x,B,'go') >> plot(x,B,'go') >> hold on >> xlabel('Distance (m)','Fontsize',21); >> ylabel('Magnetic...
  22. T

    UPS that accepts multiple power sources

    Hi, I'm looking for a device that is able to provide stable power and alternate between power sources. UPS, no matter how good they are, they usually still have several millisecond downtime during outage, switching from power grid to backup battery. I want a device that can accept power from...
  23. CCR5

    Geometric Optics and Lens Power

    Homework Statement A farsighted boy has a near point at 2.3 m and requires eyeglasses to correct his vision. Corrective lenses are available in increments in power of 0.25 diopters. The eyeglasses should have lenses of the lowest power for which the near point is no further than 25 cm. The...
  24. chasrob

    Reality check on superhero power

    My story has a Superman analogue as the protagonist. His talents include the basic “flying brick” goodies, but no other powers. Early in the story, soon after he was “transformed”, he’s flying in for a landing in his current, drug-ridden, residential neighborhood at night. He happens to look...
  25. G

    Any advice for a power electronics newbie?

    I realize there are a lot of people on this forums in a related field of study. Was wondering if there was something you wish you would have done at/from the start of your career? I am graduate student in the field and am about to start an internship soon. Was wondering if there was anything I...
  26. Mr Davis 97

    Proving the Power Series Expansion of 1/(1+x^2)

    Homework Statement Show that ##\displaystyle \frac{1}{1+x^2} = \frac{1}{x^2} - \frac{1}{x^4} + \frac{1}{x^6} - \frac{1}{x^8} + \cdots## Homework EquationsThe Attempt at a Solution I know that the power series expansion of ##\displaystyle \frac{1}{1+x^2}## about ##x=0## is ##1-x^2 + x^4 - x^6 +...
  27. Cocoleia

    Working with phasors (Circuits, such as complex power)

    Homework Statement I am going over examples in my textbook and I came across this: I don't understand how they converted 18.265 at angle of 39.9 to 14.02+j11.71 Homework Equations I know how to convert from the imaginary numbers into the angle form, usually I use: Is there another equation...
  28. S

    Steam Power Plant Reheat Efficiency Calculation

    Homework Statement Homework Equations Heat added, Qa (This I'm not sure how since the steam passed through a reheater before it enters the HPT. That is what I understand based on the problem above) Work Net, Wnet Efficiency, Wnet/Qa Heat Rate, WP/EP (Not sure if that is the correct formula)...
  29. airstrat

    Can I Use a Larger Power Bank for My LED Strip to Extend Its Battery Life?

    I have a 4.5v LED strip 14.5watts (unknown amp draw; maybe 3amp) 30 LED 5050 per meter that runs off 3 AA Alkaline batteries. It runs fine for several hours (with the AAs) which is great but Id like to hook it up to a small power bank. I pulled out an old old power bank of 2200mAh 5v 1A output...
  30. B

    Power supply for multiple devices -- effects on accuracy

    Hi, For my project I am plotting a Force vs Displacement graph using 2 analog inputs which are going to a DAQ. The two analog inputs are coming from; -A 5k potentiometer (for the displacement) -A 1000 lb load cell sensor (for the force) I would like to use a regulated 12V DC (1Amp) power...
  31. G

    Does current flow back to the power plant through the ground?

    Hi. I fear I might not have understood some fundamental concepts about electric power transmission. So we have "neutral" which is brought to Earth potential. Does this mean the electrical circuit from the power plant over highly conductive aluminium cables to my home closes back to the power...
  32. R

    How much power would this system generate from waves?

    I'm looking for some back-of-the-envelope calculations on an idea. Say there is a buoyant mass floating on the water. It is connected to a system which, when waves move the mass up and down, it pulls a string which turns a wheel of an electromagnetic generator (assume there is a mechanism...
  33. Delta Force

    Historical Power Plant Costs and Efficiencies?

    I'm wondering if anyone knows where I could find information on historical costs and efficiencies of various sources of energy (hydroelectricity, coal, petroleum, natural gas, etc.) and plant types (steam, diesel, and gas turbine), especially at facilities of various sizes. That information...
  34. B

    Clarification about a Power screw's specifications please

    Hello, I have a power screw. According to the specifications, it is M8x1.25. Does that mean the effective diameter of the thread is 8 mm while the pitch is 1.25 mm? Is the screw radius just 4mm? From the internet, it looks like the lead angle is atan(Lead/(pi*effective diameter of the thread))...
  35. uchuu-man chi

    Need help evaluating an improper integral as a power series.

    Homework Statement Evaluate the indefinite integral as a power series. What is the radius of convergence (R)? ##\int x^2ln(1+x) \, dx## Book's answer: ##\int x^2ln(1+x) dx = C + \sum_{n=1}^\infty (-1)^n \frac {x^{n+3}} {n(n+3)}; R = 1## Homework Equations Geometric series ##\frac {1} {1-x} =...
  36. HethensEnd25

    Pressure change at the inlet of a steam turbine in a small electric power plant

    Homework Statement A steam turbine in a small electric power plant is designed to accept 4500 kg of steam at 60 bar and 500oC and exhaust the stem at 10 bar. Part C. In off-peak hours, the power output of the turbine in part a) (100% efficient) is decreased by adjusting a throttling valve...
  37. C

    Increasing the Power Output of a Turbine

    I have a hydro turbine spinning at 62.746RPM and it produces 170.195Nm of torque. It generates 1.1183kW but ideally, I would like to step it up to at least 4.5kW. Is this possible using a gearbox and if so how can it be done?
  38. G

    Three-phase electric power: Household distribution

    Hi. How is three-phase electric power distributed in a household with mainly single-phase power plugs? Do they just connect a phase at random to every plug? As far as I understood, it's best if all three phases deliver the same current, since then neutral cancels. Do electricians take into...
  39. S

    Using this power level indicator to measure a power supply voltage

    In this project, I am using the https://www.amazon.com/dp/B005W09XYW/?tag=pfamazon01-20 as a power supply, but in my project, if my device shuts off suddenly without shutting off properly, it would require me to reboot the entire system as it won't work anymore. So I decided to use this power...
  40. Vikas Kasireddy

    What Are the Best Power Engineering Paper Topics for Seniors?

    I am electrical engineering senior taking a class on power generator, power distribution, and motor design. I am looking for final papers ideas. I am very interested in energy storage and its applications. One paper I found was http://ieeexplore.ieee.org/document/7362184/?reload=true. I am...
  41. P

    Low DC amp through small circuit of 14 AWG copper wire?

    I have a 2 AMP regulated DC power supply, with variable voltage 3 - 12 v. If in a small circuit, i.e, small copper wire with 1 ohm resistor. Why am i not getting at max Amps?
  42. Frov_ken

    Finding the power from the electric field amplitude

    Homework Statement I am modelling a ray-tracing algorithm(image method), and I am in the part where I am getting the summation of all EM "rays" hitting the receiver. I come to a problem where I can't properly convert and unsure to do so. Ideally, I should have a collection of Ei waves defined...
  43. M

    I Truncated Fourier transform and power spectral density

    Hello, I am trying to find an expression for the signal-to-noise ratio of an oscillating signal on top some white noise. In particular I would like to know how the SNR scales with the integration time. It is well known that during some integration time ##T##, the SNR increases as ##T^{1/2}##...
  44. gleem

    Westinghouse Bankruptcy and the Future of Nuclear Power

    Are anti-nucs dancing in the streets? Westinghouse the nuclear power branch of Toshiba has filed for bankruptcy leaving two unfinished power plants in the US and propose projects in the UK and India in limbo...
  45. I

    Finding the optical power of a contact lens

    Homework Statement A farsighted man uses eyeglasses with a refractive power of 2.05 diopters. Wearing the glasses 0.020 m from his eyes, he is able to read books held no closer than 0.265 m from his eyes. He would like a prescription for contact lenses to serve the same purpose. What is the...
  46. N

    I Power series - Different problem

    In the power series below, I've used the ratio test and at the end I got |x-2| times infinity which is >1 so it diverges.. and in this case there is no interval of convergence because it's times inifnity.. How did he conclude that it converges at x=2??
  47. N

    I Absolute Power Series: Questions & Solutions

    I've 2 questions 1) Why do we take absolute of the power series? 2) I don't get why the interval of convergence is from -inifinity to +infinity. You can find the problem below.
  48. Delta Force

    Volanic Ash and Nuclear Power Plants

    Trojan Nuclear Power Plant was located 12 miles north of St. Helens, Oregon. St. Helens, Oregon, is only 39 miles away from Mount St. Helens, which had a major volcanic eruption in 1980. The heaviest ash fell to the northwest of the volcano in Washington and to some extents Idaho, which...
  49. F

    How Can I Use a Power Supply as Both a Voltage and Current Source?

    Hello, Certain power supplies can be both a voltage source or a current source. a) Voltage source: We set the voltage to a specific value we like and change load resistor. The current will vary (get smaller for larger R) but the voltage will not vary. To make the power supply a voltage source, I...
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