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. S

    Strange problem: Replacing a battery w/ a DC power supply

    Hey everyone, So I'm trying to figure out what could be causing this problem: I have a DEWENWILS Wireless Remote Wall Switch which takes a 12V battery 60 mAh(23A battery), when I replace the battery with a 12V 500 mA DC power supply, the unit stops working properly. I'm able to use the Power...
  2. M

    How to determine the power of a rotary lobe pump?

    Want to know how to get the actual power the pump needs. I can measure the flow rate by the flow meter and count the revolutions of the pump. But selecting the proper motor for the pump would be a problem. So I want to know how to determine the power of the rotary lobe pump and generate the...
  3. Dale

    How Does Mechanical Power Flow Through Structures Like Drive Shafts and Levers?

    I am trying to determine the flow of mechanical power through a structure like a drive shaft or even a simple lever. The components of the Cauchy stress tensor, ##\sigma_{ij}##, have units of force/area, so if I multiply by the velocity, then ##\sigma_{ij} v_j## would have units of power/area...
  4. D

    Power series: radius of convergence

    ##\sum_{k=0}^\infty \frac {2^n+3^n}{4^n+5^n} x^n## in order to find the radius of convergence i apply the root test, that is ##\lim_{n \rightarrow +\infty} \sqrt [n]\frac {2^n+3^n}{4^n+5^n}## ##\lim_{n \rightarrow +\infty} \left(\frac {2^n+3^n}{4^n+5^n}\right)^\left(\frac 1 n\right)=\lim_{n...
  5. D

    Set of convergence of a Power series

    given the following ##\sum_{n=0}^\infty n^2 x^n## in order to find the radius of convergence i do as follows ##\lim_{n \rightarrow +\infty} \left |\sqrt [n]{n^2}\right|=1## hence the radius of convergence is R=##\frac 1 1=1## |x|<1 Now i have to verify how the series behaves at the...
  6. D

    Power series: Why is this power series equal to log(2)?

    ##\sum_{n=0}^\infty (-1)^n \frac {x^\left(n+1\right)}{n+1}## for x=1 ##\sum_{n=0}^\infty (-1)^n \frac {1^\left(n+1\right)}{n+1}## i've tried leibniz test but i can only find that it converges why is this power equal to ##log(2)##? i've also tried with ##\sum_{n=0}^\infty\log \left (1+\frac 1...
  7. I

    Using multiple alternators at once for a power source

    Hi I need to create a electricity generator, I've got plenty of car alternators and car batteries, all are 12v. I know how connecting batteries in parallel / series, basically i could connect like 20 car batteries to have a 12v massive amperage power bank which would cause an issue with wire...
  8. J

    Engineering Finding voltages in a linear circuit

    From the circuit I have: ##-v_b + v_a + V = 0## ##v_b - V = v_a## ##i_1 = (v_b - V)/R_1## ##I + i_2 = i_1## ##(v_b - V)/R_1 = I + v_b/R_2## From this last equation I get ##v_b = 10.8## and hence ##v_a = 5.8##. However, apparently that is wrong. (And hence my answers to #2 were all wrong as...
  9. brawler234

    Work or Net Work when calculating Power?

    When calculating power, which is Work/time, do we consider NET work (work calculated based on net force) or just work done by the individual force that goes in the same direction as the displacement? If it's the first, then power is 3W. If it's the second, then power is 5W. Which one is correct?
  10. W

    I What is power suppression in CMB experiments?

    I have heard that results form CMB experiments show a suppression of power at large angular scales. Can someone explain what "suppression of power" means in laymen terms in this context?
  11. E

    I'd like to find a power bank circuit with 2.7V input

    Hey, can you find me a power bank circuit which has 2.7V input?? Because I'm in a project which makes power bank with super capacitor, and you knows that we can't input voltage above the maximum voltage of capacitor, right? You can refer this video. Thanks.
  12. R

    What is the electrical power output of a turbofan engine?

    Hello All, Happy New Year! A typical modern turbofan engine system creates lift as well as propulsion for the aircraft. Somewhere inside the system, the fast rotating device also works as a generator (alternator) to produce the electricity powering electrical/electronics equipments. What is the...
  13. Saracen Rue

    I Intersections between this infinite power tower and a multifactorial

    For those unaware of multifactorial notation, it should be noted that there are some common mistakes made when first being introduced to the notation. For example, ##n! \neq (n!)!## and ##n! \neq (n!)! \neq (n!)! \neq ((n!)!)!##. Just to make sure we're all up to speed, here's a quick run down...
  14. F

    Power, current, voltage transfer principles

    Hello, I have been reading about impedance matching as being the main requirement to ensure maximum "power" transfer from one part of a circuit to another: the two electric systems ##A## and ##B## need to have complex conjugate impedance so only 50% of the energy is reflected back at their...
  15. Saracen Rue

    I Find the intersection point of an infinite power tower and a primorial

    Consider ##f(x) = {^{\infty}x} = x \uparrow \uparrow \infty## and ##g(x)=p_{x}###, where ##p_x### is the primorial function and is defined such that ##p_n### is the product of the first ##n## prime numbers. For example, ##p_{4}### ##= 2×3×5×7=210## Let the point of intersection be defined as...
  16. Piotrovskiy Yury

    Is 2000 Kilocalories the Average Human Need per Day?

    Human power 97 watts? 2000 kilocalories is the average human need per day. 2000 kilocalories is 8373.6 kilojoules divided by 86,400 seconds in days = 97 watts.
  17. arcTomato

    Comp Sci Power spectrum when the wave number is not an integer

    Hi all. I made a program of DFT, so I made the power spectrum of a sin wave. This is the sin wave I used. All data number ##N=100## and the frequency of sine wave is 4.5Hz. And the power spectrum is this. The wave number is not integer so the spectrum has the side lobe. But I think this is...
  18. D

    Poynting vector -- Calculate the EM power transmitted down a coax cable

    I don't know which part gets wrong
  19. bieon

    Finding the Power Produced by a Hydroelectric Generator

    My Attempt So Far: 1. Write down all information: Q=10m³ /min h=75m 2. Change 10m³ /min to m³ /s 10m³ /min × min/60s =1/6 m³ /s 3. Change Volumetric Flow Rate to Mass Flow Rate ṁ=ρQ ṁ=1000kg/m³ × 1/6 m³ /s ṁ=166.67 kg/s 4. Apply Potential Gravitational energy but replacing the Mass with...
  20. AlexCaledin

    "Class-B" Audio Power Amp with "Current Pumping"

    Hello everyone, I was thinking how to cancel the class B crossover distortion, may I suggest to discuss an interesting variant. Let's start from this: - there is crossover distortion (and no current protection). The signal source is "full voltage, zero current". Let's make it "full current...
  21. Y

    Power and Mass Question -- A helicopter accelerating and ascending

    I started with calculating the Ep and Ek of the helicopter and got this: Epi = 490m Eki= (1/2)(400m) Epf = 12740m Ekf = (1/2)(1681m) I don't really know where to go from there. Do the unknown mass variables cancel out? I'm lost!
  22. V

    The power of a multistage compressor

    is there any equation to find the work done, power and efficiency of a multistage compressor with a summation of calculating the power as so, instead of calculating individual power and summing at the end. any citiations is also good to know. thanking you, with regards, vishnuvardhan
  23. J

    Engineering Relationship between total Rotor Power and Losses

    Equations: Pr : Pm : Pc = 1 : 1-S : S Total Power into rotor: Pr=I'22R'2/S Mechanical Power Output: Pm=I'22R'2(1-S)/S Power loss in rotor: Pc=I'22R'2So I'm a little skeptical of my answer here. Seems a little too easy, which normally means I've missed to mark by about 100 miles. Attempt...
  24. Kaguro

    I Solving an ODE with power series

    I have an ODE: (x-1)y'' + (3x-1)y' + y = 0 I need to find the solution about x=0. Since this is an ordinary point, I can use the regular power series solution. Let y = ## \sum_{r=0}^\infty a_r x^r ## after finding the derivatives and putting in the ODE, I have: ## \sum_{r=0}^\infty a_r...
  25. arcTomato

    The power spectrum of Poisson noise

    Dear all. I have made the power spectrum of Poisson noise(expected value ##λ=2##), and it becomes like this I think this is not good. I don't know why the power is so high when Random variable(x axis) is 0. I tried another expected value version ,but the result didn't change. so I would like to...
  26. J

    Introductory Circuit Analysis—power ratings

    I am going through "Circuit Analysis for Dummies". On pg 18, it says, "If you calculate the power dissipated as 0.1 watts, then a 0.25-watt resistor can handle this amount of power. A 0.125-watt resistor should be able to handle that amount as well, but when it comes to power ratings, err on the...
  27. arcTomato

    I I would like to know the calculation process of this power spectrum

    Summary: Derive the formula of power spectrum from Discrete Fourier Transform. Hi all I don't know where should I post this, so if I am wrong, I apologize.(But this is almost math problem so ) I would like to know the calculation process when derive Eq(6.3) in this paper. Eq 2.4a is...
  28. D

    A In the power spectrum, why is the peak frequency at the first harmonic

    l
  29. P

    Max Power of a Tesla SUV: Solving F(net)=F(app)-F(resistance)

    F(net)=F(app)-F(resistance) ma=F(app)-F(resistance) (1.5*10^3)(16.67)=F(app)-600 25005=F(app)-600 P=ΔE/Δt P=25005/6 P=4167.5 W I got the incorrect answer (because I didn't take into account the resistance?). I am also confused about which Force value to use for the...
  30. C

    Optics focal length and optical power Question

    1/f = 1/dₒ + 1/dᵢ = 1/1.0 + 1/0.33 = 4.03 m (focal length) Power: 1/4.03 m or 0.248 (0.25) *around to the2 decimal points? or leave it as a fraction? ((Did I do this correctly? I am not sure if this is correct and is it okay to be in meters not centimeters?)) Please let me know!
  31. Saracen Rue

    I Area enclosed by a function involving 2 power towers

    I've been playing around with Up-Arrow notation quite a lot lately and have come up with the following "thought experiment" so to speak. Consider the following function: $$f(x)=(−ln(x↑↑(2k)))↑↑(2k+1)$$ $$\text{Where }k∈\mathbb{Z} ^+$$ In the image below we can see some examples of what this...
  32. arcTomato

    Engineering The power spectrum of a sine wave (C language)

    Hi I would like to Derive the power spectrum of sinusoid.I tried like this. But It doesn't work. <Moderator: CODE tags added> #include <stdio.h> #include <math.h> #define pi 3.1415926535 FILE *in_file, *out_file; int main() { dft(); } int dft(int argc, char *argv[]) { char...
  33. pkress

    Engineering Minimum Critical Power Ratio (nuclear engineering applications)

    Im having a really tough time with this problem, I am assuming that in order for q'(z) to be a maximum, e^(-az/L)sin (pi(z)/L) must be a maximum. I believe this occurs when the derivative with respect to with respect to z/L is zero, which gives me z = 0.322L, but I am not sure if this is correct...
  34. A

    Power delivered/Internal work done by a car's engine

    Attached is an example from my Tipler physics book of a determining the power delivered from a cars engine. I get the derivation(math), but am having some issues with the understanding/concept. Mainly, isn't Power=Work done/time. If so, they define the system as Car-earth. There is no external...
  35. J

    Wireless Power Transfer (is this correct)

    Ref: https://www.semanticscholar.org/paper/Design-and-Simulation-of-Different-Wireless-Power-Baroi-Isla m/dc19ecfde904964704777ab5adef96d5d6846f1f I couldn't find the working of this circuit so I guess it would be like: Initially transistor is OFF, so the current flows through Base, and...
  36. garthenar

    Power related to the EMF of an adjustable coil in a magnetic field

    I'm already stuck on A. I'm hoping once I figure that out the rest will just fall into place but be prepared for this to take awhile. I understand how to use Faraday's law to get the current or voltage of the system based off the movement of the bar but I have no Idea how to relate the rate of...
  37. D

    Sound power: What is 100mW amplified by 2dB?

    100mW = 20 dBm, that is then amplified by 2dB 20dBm/2dB = 10mW so power out of the amplifier would be 100mW+10mW =110mW?
  38. engnrshyckh

    Power supplied by a Capacitor and Inductor

    Using above eq Xc=80.38Ohm and P=179VAR but textbook says that the ans is zero. Can anyone explain please
  39. J

    Power output from a falling masss over a time period

    How did you find PF?: youtube [Moderator: moved from new member intro forum]How did you find PF?: youtube i need a falling mass over time /joules per kilo over 1hr time also need to know how to figure gearing to maintain fall over time in regards to a set resistance such as a 5 kw alternator
  40. M

    Engineering Homework: Rx=? to get maximum power transfer at point M

    Hi, after calculations I end up in the circuit below¨ (Thevenin equivalent) So now I have to say Rth=RL and I will find Rx ?The initial circuit is this: Thanks
  41. L

    How to determine the power of this circuit?

    In "Homework Equations" field, I wrote general equations for quadripole. I have doubt about the solution. True answer given in the electrical engineering textbook is P = 100 W. Here is my solution: 1) In scheme, I pointed currents and U(output) (Fig. 2). 2) U = A*U(output) + B*I2 I1 =...
  42. Boltzman Oscillation

    Can Ohm's Law Be Defied with Independent Power Sources?

    In my study of electrical engineering I have been told that the voltage across a resistance is V = IR. If I connect a resistor R and a power supply of 5V 2 A then how does ohms law work here? I could change R to anything I want but the source would stay at 5 V and 2 amps regardless of what I do...
  43. fpjeepy

    When the world doesn't understand energy and power

    :cry:
  44. CricK0es

    How can I evaluate the power produced by a WEC unit? (wave energy)

    I'm currently researching if I could implement some wave energy into my small scale hypothetical project. I've identified some commercial models, namely Seabased and SINNPower, and I assumed that they would have approximate values of power output given wave period, height (among many other...
  45. Mimosapudica

    Calculating the power delivered when a block of mass m slides along

    Force along the horizontal would be T cos(theta) Frictional force (which is in the opposite direction )= μmg So net force in the direction of velocity = Tcos(theta)-μmg P= [Tcos(theta)-μmg]v But this is not so, the right answer is given to be Tvcos(theta). Why should we not consider the...
  46. Mimosapudica

    Power developed by a person on eating 100g of ice per minute is?

    P=W/t W=Q= mL = (100x 80x 4.2)/1000 (kg x J/kg) = 33.6 t= 1 minute= 60s P= 33.6/60= 0.56 watt... but the answer provided is 560J/s...?
  47. N

    Can you help me calculate the required torque and power of this motor?

    Hi everyone, I want to rotate this (see attached image) platform at a speed of 20 RPM. To this end, I have to calculate the torque and power of a motor required. I have done preliminary calculations, however the numbers I'm getting doesn't seem right. For example, I'm getting that the torque...
  48. BillTre

    How to Deal with No Power in Areas of California

    Some areas of California are going to have their power turned off to prevent wild fires like they had last year. I don't live there, so lucky me. Its my understanding that some of the fires were started by wires blowing around and causing sparks in some way. Apparently, the power may be off for...
  49. P

    Power flow in a TE mode for a rectangular waveguide

    $$\frac{dP_{flow}}{dA} = \frac{1}{2} Re \{\vec{E} \times \vec{H^*} \} \cdot \hat{z}$$ since ##E_z = 0## everywhere ##\vec{E} = \vec{E_t}##$$\frac{dP_{flow}}{dA} = \frac{1}{2} Re \{\vec{E_t} \times \vec{H^*} \} \cdot \hat{z}$$ $$\frac{1}{2} Re \left\{\mp Z_{TE} \left[ \left(\hat{z} \times...
  50. Adrian Tudini

    Computer models that predict the maximum power of a chemical reaction

    Given a balanced chemical equation, can we predict using computer models the maximum power of the chemical reaction? Thanks.
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