Power Definition and 998 Threads

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...

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...

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...

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

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

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.

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##...

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...

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)...

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...

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...

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...

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...

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...

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

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...

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...

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...

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...

That's about it. I've been trying to do the calculation manually with Bethe-Bloche without corrections in the energy range I'm interested in (1-10 MeV) for the highest Z material with data available for validation (Uranium), but I can't get a result that agree well with the database, so I'm...

I know that the answer for A is 31.82. But when i look up B why is it zero? can someone explain please thank you

I am using a power supply (30 kV, 20 kHz) to discharge in air between two electrodes separated by an insulator. For 30 kV applied voltage, oscilloscope shows only 6 kV, and no discharge occurs. What are possible problems and solutions?

I have a power strip that has fallen from height accidentally for a couple of times, there is no observable crack or damage, however, could this lead to bad contacts or anything bad to the electrical/electronic appliance? I'm thinking if the power cable inside is usually well attached

e=QxV t=Q/I p=(QxV)/(Q/I) =V/I The expression I came up with for a) is the potential difference divided by current to get power but I have no idea if that is even right if someone could just prompt me in the right direction that would be greatly appreciated

First, here is a riddle: Why did the tortoise cross the road? Because an under-pass was available. An adventurer and desert explorer visited and tried to explain the workings of the solar powered towers at Ivanpah, in the Mojave Desert in California. The person is not any kind of scientist nor...

Hello: I'm confused about transmission lines. According to Faraday's Law, what's induced is an emf that depends on how fast the coils spin, or whatever equivalent to a simple model seen on Physics textbooks. Power, however, is then assumed constant when talking about the power loss due to...

(This is my first time posting here, sorry in advance for any difficulties. ) All componenets of same type has same magnitude, so e.g. the two resistors both have $R$ resistance. Given the difficulty of the previous exercises, I believe I'm over complicating the problem. However, here is what...

Hello, It is well understood that a constant horizontal force ##F_{applied}## applied to an object of mass ##m## over a distance ##d## in a direction that is not orthogonal to the direction of motion produces mechanical work ##W= F d ##. This work is a mechanism to inject (or subtract) energy...

I see there has been threads about Blackbird and "Down Wind Faster Than The Wind" operating principle in general, and I see a good number of people (most?) in those threads seemed to pick up some understanding of how it actually works. So that's a good start and gives me hope. I had never heard...

Can someone please tell me why this is true? This isn't exactly the De Moivre's theorem. Thank you.

High! I have a EM plane wave hitting normally a surface dividing universe in media 1 and 2, both without losses. So we have incident, reflected and transmitted waves. It's a simple exercise in which you are given the basic data about two media and wave incident amplitude H in medium 1. I get...

In winter I heat my workshop with a radiant heater and an oil heater. Easy to know how much heat is entering the room. But in spring and summer I don't use those; I blow hot air from the ceiling cavity into the room, and I was wondering how I would estimate the heating power and the formula to...

Hi, I understand that if there are two signals whose spectrums consist of different set of frequencies, they can be separated using a filter such as bandpass filter on the receiver end. Is it possible to separate two signals who frequency spectrums are the same but power levels are different?

Summary:: I can’t get the correct answers, I think I haven’t fully understand the theory behind them The answers are given in the picture

Summary:: I don't seem to see any problem with my work. But my final answer does not match the correct answer. (In number 3) Here's my work

Hello PF. I am thinking about the power spectrum when observing X-rays. We are trying to obtain the power spectrum by applying a window function ##w(t)## to a light curve ##a(t)## and then Fourier transforming it. I have seen the following definition of power spectrum ##P(\omega)##. Suppose...

In a plasma device, the plasma is generated by applying high voltage in a gas. What are the specifications for the power supply producing such plasma? The output must be AC or DC? Pulsed or not? What are the current, voltage, etc...?

Induction motors: pf = 0.8 triangle: θ = arccos(0.8) = 36.86 degrees Pa = 500/0.8 = 625 VA Pr = sqrt(625^2-500^2) = 375 VAR Synchronous motors: pf = 0.707 triangle: θ = arccos(0.707) = 45 degrees Pa = 500/0.707 = 707 VA Pr = sqrt(707^2-500^2) = 499.85 VAR I am uncertain of how I can...

Given the following input parameters: Parameter Value Rs (Resistance through stator) 1.4 Ω Rr (Resistance through stator) 0.7 Ω Ls (stator inductance) = Lr (rotor inductance) 0.002 H xs = xr = 2*π*f*Ls 0.6283i Ω Lm(magnetic inductance) 0.01 H xm = 2*π*f*Lm 3.1415iΩ f (frequency)...

Hi guys I am struggling to find the power dissipated in the total circuit , my answer didn't match the solution in the book the circuit is simple i used Kirchhoffs rules to find the following : loop 1 : $$10-10I_{1}-40I_{3} = 0$$ loop 2: $$20-20I_{2}-40I_{3} = 0$$ and $$ I_{1}+I_{2}=I_{3}$$...

I tried to solve it by integrating force from 0 to L dF=dm.g where dm=λdx And then I multiplied it with velocity to get power because velocity is constant ∫(vdF)=v ∫(dF) But the book used integration to find work done and divided it by time for power My answer was λlgv(Option B) Giving...

How did you find PF?: Trying to find answers Hi I’m trying to solve this problem .hope someone can find the answers, I need to find the hp needed to run a flying wheel ring shape. 42 ft in diameter weight 200.000 lbs the wheel is Suport by bearing inside and out of the edge of the rim, the...

I understand that Zener Breakdown occurs when the reverse current starts flowing in the junction because of which depletion region entirely vanishes. Can I power things using this reverse current ? Or will it damage the appliance?

So I've done part a) Primary current = 200000/415=481.9 Cos θ = -0.8 Sin θ = 0.6 Reg=(481.9 ( 0.014*-0.8 + 0.057*0.6))/415 = 0.0267 Reg% = 2.67% Part b I simply used the same equation but for secondary: @ unity p.f., cos θ =1, sin θ = 0 secondary current = 200000/11000 = 18.18...

Given the AC Induction (asynchronous motor) in 3 phases: Parameter Value Pn (Nominal Power) = Pmechanical (output power at the shaft) 5 kW = 5000W uls (Voltage through the stator line) 220 V fstator (stator frequency) 50 Hz p (Number of pole pairs) 2 LFe (Iron loss) = Lmechanical...

I am looking for the right size of battery/pure sine-wave inverter to power a system for a few hour when there is a power outage. The system of TV/DVD/Internet uses less than 200 watts at about 1.6Amps. I could just buy a commercial system which runs about 1000$ or assemble a similar design for...

Using log identities: ##log((\alpha - 1)!^2) = 2(log(\alpha - 1)!)## Then apply Stirling's Approximation ##(2[(\alpha - 1)log(\alpha - 1) - (\alpha - 1)## ## = 2(\alpha -1)log(\alpha -1) - 2\alpha+2## Is this correct? I can't find a way to check this computationally.

I first worked out the buoyant force using rho = 1000, g = 9.8 and V = 1. (this gives Fb = 9800) I then worked out Fg of the tank (5 x 9.8 = 49) Then I used Fnet = Fb - Fg - T = 0 to work out tension as 9751. I thought the work done would be the work done by tension (9751 x 50.4), but I'm not...

I thought that if we Fourier transformed the counts of the sum of the signal from the source and the Poisson noise, and obtained the power spectrum, we would get the following, ##P_{j}=P_{j, \text { signal }}+P_{j, \text { noise }}+\text { cross terms }## but I found the following description...

Hi, I have a 1 HP motor spinning a turntable (just a wheel) weighing 1kg, diameter 25cm speed 2000rpm. (Arbitrary specs). If I have to spin a turntable with the same weight (1kg) but double the diameter (50cm) at the same speed, would I necessarily need a motor with double the power (2 HP)...