# 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. ### I I'm slightly confused about the power spectrum of matter

How do you get these scalings for the matter power spectrum?$$P_{\Delta}(k) \sim \begin{cases} k & \quad k < k_{\mathrm{eq}} \\ k^{-3} & \quad k >k_{\mathrm{eq}} \end{cases}$$(N.B. ##k_{\mathrm{eq}}## is the scale of modes that enter the horizon ##k \sim \mathcal{H}## at matter-radiation...
2. ### I Power transfer Halbach or dipole

Good morning, I followed this thread https://www.physicsforums.com/threads/halbach-array-arrangement-for-a-transformer.979745/, about wireless power transmission using a Halbach array and @Baluncore answers are were very satisfying. Here are two configurations, the first is a resonant dipole...
3. ### Clarify power calculation

I have a nozzle through which a water vapour passes at 503 metres per second with a density of 0.051 kg per cubic metre giving a mass flow rate of 0.00129 kg per second. Using half mass times velocity squared I have an answer of 163. Is that answer 163 newtons and if it is how do I convert to...
4. ### B Is the time derivate of force equal to the position derivative power?

Is this wrong?
5. ### Help using Atlas Silvaco to simulate an OLED

I am trying to simulate an OLED via Atlas SilvacoI want to know how to convert light power (watt/um) into luminance (cd/m2) or the syntax to do that in Atlas silvaco.THANKS
6. ### B Identity Theorem for power series

Consider this proof: Is it a valid proof? When we divide by ##z##, we assume that ##z \neq 0##. So, we cannot put ##z=0## on the next step. IOW, after dividing by ##z## we only know that $$c_1+c_2z+c_3z^2+...=d_1+d_2z+d_3z^2+...$$ in a neighborhood of ##0## excluding ##0##.
7. ### B How to convert ft-lbs/sec to Newtons?

Hi, How to convert 51065 foot pound per second to Newtons, not Newtons meter per second?
8. ### Ring roller power

In principle, the ring is, at any instant, a beam being loaded in the centre, and in a failing state. Thus, to drive the material continuously through the rollers, Force x Velocity = Work done/time = power. 60.P/2.pi.N = T The units pan out, but is the concept correct? The faster the work is...
9. ### Does an aerial punch or kick transfer more power than a standing one?

All else, equal, does an airborne technique transfer more power? I don't think it does but an instructional tape from the 80s claim so
10. ### New High Efficiency Power Lines

I read an interesting article on progress in making transmission lines more efficient: https://reneweconomy.com.au/super-cheap-transmission-upgrades-could-double-capacity-and-open-floodgates-for-renewables/ While, of course, we do not discuss politics here, this new technology has many...
11. ### Measuring Power output of DC generator

Hello everyone, I would like to ask some questions regarding my thesis. I have a problem identifying which load I should use to calculate the power output of the small generator. I use an Archimedes screw turbine as the prime mover of my generator, and the water flow is low in my locality...
12. ### Avg Power in a Rotational Energy/Work Problem

This question has multiple parts and according to all the work done up to this point... How much work W does the motor do on the platform during this process? 1885 J What is the rotational kinetic energy of the platform Krot,f at the end of the process described above? 1885 J What is the...
13. ### How Do Pulleys Multiply Force in Complex Systems?

many pulleys at various angles multiply the initial power of the winch
14. ### I Sound power, amplitude, frequency, and decibels

Hello, It has been difficult to find a clear answer to this question. I've found some sources stating that the power of a sound wave depends upon both amplitude and frequency. I've found other sources stating that the power of a sound only depends on amplitude. I've found sources stating...
15. ### POWER - different approach, different results

Basically, I tried to find the solution by calculating P=Fs/t, where F= 2250 and s is the distance traveled in the 12th second and that result differs from the result I get when I calculate the power using P=Fv. ##F=ma=1500*1.5=2250N## ##s_{12}-s_{11}=...
16. ### Work Done and Acceleration (Mistaken Answers?)

So for Q1, I answered down (towards Earth) but the solution says there is no acceleration there. For Q2, I answered mgh, but the solution says it's mgh/t, which is power, right? I just want to make sure I'm not super confused. Thank you.
17. ### I Power done by work on a continuous body isn't the derivative of work?

The definition of work and power done over a continuous body is: $$W = \int Tn \cdot u dA + \int b \cdot u dV$$ $$P = \int Tn \cdot v dA + \int b \cdot v dV$$ ##T## is the stress tensor, ##b## is the body force, ##u## is the displacement vector, ##v## is the velocity, ##n## is the normal...
18. ### Power delivered to wheels of car with constant air resistance

For part (a) the answer key is saying it's 40 hp. I'm having trouble understanding this. So the car accelerates to 15 m/s, then it stays at that velocity of 15 m/s, needing only 20 hp power to overcome the work done by air resistance. Supposing the car then accelerates to 30 m/s and stays at...
19. ### Heater power keeping a room constantly warm from low temperatures outside

I've been trying for 45 minutes and doing research but I can't even find a start to how to approach this. :( [Mentor Note: New user reminded to always show their work on schoolwork problems. That work is shown in a subsequent post below]
20. ### B How much electricity is required to create a magnetic field as large & strong as the Earth's?

How much power (Megawatts) would it require if we were to create a magnetic field as large and strong as the Earth's magnetic field?. I haven't learned how to calculate this, but just curious.
21. ### Do they have powerful battery packs that can run a vacuum?

For those that have to vacuum large spaces often have to use many different outlets and worry about running over their own cord. Is there a battery pack one can strap to their back to power a vacuum cleaner? Or would that amount of power tide to a person be dangerous?

23. ### Question on height of a jump in terms of Power (from WPE chapter, JEE level)

I used the formula P = 1/2 mv^2/t. Then multiplied by s on both sides to get P.s = 1/2 x mv^2/t x s ==> P.s = 1/2mv^3 and then expressed v = root(2gh) and equated. BUT I Got h = (1/2g) x (2sP/m)^2/3 but the answer is h = (1/2g) x (4sP/m)^2/3 Any idea where I am going wrong?
24. ### Solving for Masses in an Atwood Machine

I've tried to solve this exercise but I haven't used one of the properties of the system (the displacement of the masses) so I don't know if I'm wrong about my procedure. First of all, we (obviously) know that $$P=P$$ And since we can express the power of a force in two different ways, we...
25. ### Maximum power from a transformer

Hi, I was having a discussion with a colleague today now I'm second guessing myself. My understanding of nameplate kVA is that it is based on 'ambient temperature, temperature rise, heat transfer, thermal mass, thermal time constant, materials used, and expected transformer life'. However...
26. ### Average thermal power produced

I'm curious as to why the average power is not negative in this scenario, since I thought the friction force is in the opposite direction of velocity. As far as I see friction force is the only acting force in the problem, but I may be wrong. I solved this by simply doing (Friction Force *...
27. ### I Relationship between frequency and power for sound?

Hello, I have a problem wrapping my head around the relationship between frequency, power/pressure, and displacement. Let's say I have two sine waves that I generated in my computer: A 50 Hz tone and a 100 Hz tone. Let's say they both have an amplitude of 1. Therefore, they will both have...
28. ### I Is the Poynting Vector Field the Only Factor in Energy Flow in Circuits?

In a simple circuit consisting of a battery and a resistor, current will flow if the circuit is closed. Resistor uses the energy provided by the battery, creating heat with a power ##P = UI##, where ##U## is a voltage across the resistor and ##I## is a current through the resistor. In my...
29. ### Power output and sound intensity

In the picture below
30. ### Maximizing Power Transfer: An Analysis of Resistance and Efficiency

I equated dP/dR to 0 and find the solution for R. Is the solution correct?
31. ### Exploring the Average Power of an Elevator: A Physics Perspective

The answer in the book is 400w. It said that ##P_{av}=Fv_{av}cos(F,v)=mgv_{av}cos(F,v)=400##w and F is upward force that is applied by elevator. Should velocity of the elevator be constant? Because it said that we have F=mg.
32. ### How much of an approximation are power measuring tools for martial arts?

For instance this Power Cube device. Is it capable of reporting EXACTLY how hard Francis Ngannou punched, or will it be biased towards mass or speed and overestimate one of the components? How "off" from the actual physics of reality do you expect such a tool to be? 5%? 10%? 20%?
33. ### Computer powered off, despite being plugged in. Battery wasn't charging...

Hi, So, PC powered of all the sudden, wont power on. Battery had not been charging when PC was plugged in. So, can I conclude neither battery nor power cord are working well? I guess my options for doing something to have battery recharge are limited, given PC won't power on. Do I have any...
34. ### Engineering Power dissipation of 2 diodes (1 is a Zener diode)

Are my equations correct? And my process of how I should solved this problem?
35. ### Find power needed to fly this airplane using momentum considerations

I just don't understand should I take u relative to the plane or relative to the ground. I tried to solve it like this: $$p_{final}=m_{0}v-m(u-v)-M(u-v)$$ $$p_{initial}=m_{0}v$$ $$\Delta p=-m(u-v)-M(u-v)$$ ##m_0## is mass of the plane. $$F=\Delta p$$ $$F=-m(u-v)-M(u-v)=(m+M)(v-u)$$...

37. ### Expectation value of an operator to the power of n

hi all how do I prove that $$<A^{n}>=<A>^{n}$$ It seems intuitive but how do I rigorously prove it, My attempt was like , the LHS can be written as: $$\bra{\Psi}\hat{A}.\hat{A}.\hat{A}...\ket{\Psi}=\lambda^{n} \bra{\Psi}\ket{\Psi}=\lambda^{n}\delta_{ii}=\lambda^{n}$$ and the RHS equal: ...
38. ### B Magnetic field and generator power output

Hi, I am confused about whether decreasing the magnetic field used for a generator could increase the generator's power output. I used four equations: 1. Torque = Force x radius 2. Torque = NIAB (N = number of turns, I = current, A = area of armature, B = magnetic field). 3. emf =...
39. ### Should the power supply float or be grounded?

I have read pros and cons for both, but would like to hear what people have to say. I can build a simple power supply for a project that supplies 15v that is isolated from earth ground by using the output from a step-down transformer. I can also put one together that shares earth ground. Which...
40. ### B Could solar sails be used as turbines for power generation?

It seems as though two advantages to using a solar sail turbine system instead of solar panels would be (1) the sails may not degrade as quickly as the solar panels, and (2) a sail turbine system may be lighter than a solar panel (and therefore less expensive to launch into orbit). The drawback...
41. ### MCNP terminology question -- Effective Full Power Days (EFPDs)

for MCNP users, i would like to ask about terminologies: if i depleted a fuel assembly under constant power, is the number of days in the out can be used as Effective Full Power Days (EFPDs), or this term has another specific meaning?
42. ### Converting oscilloscope voltage to laser power

Hello! I have this photodiode which I connect to an oscilloscope using a normal BNC cable to an oscilloscope, terminated with a 50 Ohm resistor. I measure the output from an optical cavity (which is basically laser light), which in my case looks like a flat signal close to zero, and regular...
43. ### Power Efficiency of Linear Piezo Electric Motors

Hi I want to know the power efficiency of linear piezo electric motors in percentile.
44. ### Outlet adapter to mimic a car battery to power 12V devices

Sorry if this is a very simple question but i have been googling and looking around for a straight anwser but can seem to find a solid answere or draw a solid conclusion from information I've reached. So I have a rgb led light for a car, the box says input 12vDC. if I wanted to set these up...
45. ### If we have a non combustible power source

If i create a non combustible self-sustaining energy source that generates zero radiation, what kind of propulsion system could be designed? Is someone out there with that type of propulsion system already?
46. ### Maximizing Range/Time in Air of an Airplane: Solving with Calculus

Is my solution correct? (I only have answers to odd-numbered exercises.) Is it a good solution or have I overcomplicated things? (a) The forward force provided by the engine balances the air resistance force, so ##F_{engine}=F_{air} = \alpha v^2 + \beta /v{^2}##. Let ##W_{engine}## be the...
47. ### A Margules' Power Series Formula: Deriving Coefficients

Margules suggested a power series formula for expressing the activity composition variation of a binary system. lnγ1=α1x2+(1/2)α2x2^2+(1/3)α3x2^3+... lnγ2=β1x1+(1/2)β2x1^2+(1/3)β3x1^3+... Applying the Gibbs-Duhem equation with ignoring coefficients αi's and βi's higher than i=3, we can obtain...
48. ### Power consumption of astable multivibrator

Hi I was wondering about the astable multivibrator . Does the circuit consume power while the diode if off ? If yes how much ? Please explain in detail. Thanks
49. ### Power factor of a retrofitted LED unit in a fluorescent fitting

A poster on another forum has fitted a large number of 230V 50Hz 24W nominal LED tubes, apparently designed to be plugged straight into the old fluorescent fittings. He has found, by clamp meter measurement, that the new LED lights appear to be consuming 80W, not the claimed 24W. A number of...
50. ### B Canadian Antineutrino Detector detects Nuclear Power Plants from 240km

The SNO+ Experiment in Canada is still in development, but analysis of early antineutrino detections as published in Physics Review Letters and as referenced in the SNO+ results page are believed to be from appear to be the from Ontario reactors 240Km away.