Power Definition and 998 Threads

Homework Statement I'm having issues understanding a mistake that I'm making, any assistance is appreciated! I know a counterexample but my attempt at proving the proposition is what's troubling me. Prove or disprove $$P(A \cup B) \subseteq P(A) \cup P(B) $$ Homework EquationsThe Attempt at...

I'm not disputing that front brakes on a vehicle provide the majority of stopping power, but why is that? I originally thought it was because of added traction at the front due to weight transfer, but even my bike moving at a walking pace has more powerful front brakes than the identical rear...

Homework Statement Homework Equations The Attempt at a Solution I solve question a) by rearranging the F=m*a equation, which makes the acceleration equal to (24N/18kg)=1.30m/s^2. And I find the final speed using equation W=1/2*m*v^2 and rearranging it to solve for v, which gives me a value...

Homework Statement Star 1 emits energy at a rate that is 2 times that of Star 2. If Star 1 also has a radius that is 3 times larger than Star 2, how do the temperatures of the stars compare? a. Star 1's temperature is 2.58 that of Star 2. b. Star 1's temperature is 3.75 that of Star 2. c...

Greg Bernhardt submitted a new blog post When Vehicle Power Dictates Acceleration Continue reading the Original Blog Post.

Hi! I want to build some cooling with peltier elements. At home I get 230V from power outlet and the maximum allowed power consumption is 15A. However, when I look at peltier elements at online store I notice that amps go up fast. Like some 12V 180W peltier is already 15A. Does this mean that I...

Homework Statement I need to solve the DE y’ = x^2y using the power series method Homework Equations y = sum(0->inf)Cnx^n y’ = sum(1->inf)nCnx^(n-1) The Attempt at a Solution I plug in the previous two equations into the DE. What is the general procedure for these problems after that...

Solar generation results for US are out for 2017. Year over year: http://www.eia.gov/electricity/annual/html/epa_01_02.html https://www.eia.gov/electricity/annual/pdf/epa.pdf US: Net Generation (Thousand Megawatthours) 2014 Solar: 17691 (that's 0.43%) All sources: 4093606 US: Net Generation...

Homework Statement Describe an auto-transformer starter. From the expression for power input per phase (∝ torque) show that for a turns ratio (n) of √3:1 , for the auto-transformer: Homework Equations Pin (phase) = 3 V I cos∅ I = V/Z cos∅ = R/Z T∝I∧2 T∝V∧2 For auto transformer with...

I am reading Stephen Abbott's book: "Understanding Analysis" (Second Edition) ... I am focused on Chapter 6: Sequences and Series of Functions ... and in particular on power series ... I need some help to understand Theorem 6.5.1 ... specifically, some remarks that Abbott makes after the proof...

Homework Statement Hello, I need to find an expression for the sum of the given power series The Attempt at a Solution I think that one has to use a known Maclaurin series, for example the series of e^x. I know that I can rewrite , which makes the expression even more similar to the...

What competency matrix are suggested for power consultant engineers? My work organization has a competency matrix of different skills. The skills included different software packages and engineering practices for low/medium/high voltage power design and instrument and controls. Some of the...

Homework Statement We know that V(t) = f(t) and I(t) = g(t), which have been found by Fourier Series analysis and some approximations. The next part of the problem is about finding the average power disappated by the system. I was wondering whether I would be able to take averages of both of...

I am new to the world of calculus and the first thing that I learned is how to calculate the area under the range of a polynomial function, like: $$\int_1^3 x^2 \,dx$$ when I take the intergal of ##x^2##, I get ##\frac{x^3}{3}##due to the power rule, but it doesn’t make sense to me,why would...

As we know, POWER is what accelerate a car, FORCE itself doesn't accelerate a car, if FORCE cousing movement it change into work, and work over time = POWER. The FORCE from jet engine pushes a plane forward. But as we know (or I'am wrong) FORCE don't push enything, only POWER couses...

Homework Statement Calculate the power needed to heat a 1360 gram chunk of ice in a 600 gram copper pan from 0 ◦C to the system’s final temperature of 35◦C in a time of 10 minutes. Homework Equations Q=mcchange in temp Q=mLf P= energy/time The Attempt at a Solution I thought that adding the...

Homework Statement Calculate average power output for a 75 kilogram person walking from ground level up stairs to a final height of 100 feet (then stops) in a time of 3 minutes Homework Equations P= work/ time or P=Fv The Attempt at a Solution I thought this was more of an energy problem...

Maybe stupid question but it confuses me:) For Example engine produces 100Nm of torque at 3000RPM. So that's mean that this 100Nm at 3000RPM in this particular moment is static force? Because torque doesn't move anything. If it start to spin, it doing work and work over time is POWER. (~43Hp at...

Hi guys, We have a industrial connection of 225 kW. Our industry consists mostly of Induction motors and runs in night shift mostly. So we use capacitor banks for lower factor correction. And so far we have maintained 0.995-0.999 pf (sometimes even 1) over the years. Previously, the power...

Homework Statement An isotropic point source radiates electromagnetic energy, and its output is measured by a thin disc-like detector of radius R. Calculate the power measured by the detector at distance h from the source, assuming that the plane of the disc is orthogonal to the line of sight...

Homework Statement The power output of an automobile engine is directly proportional to the mass of air that can be forced into the volume of the engine’s cylinders to react chemically with gasoline. Many cars (like a 2008 Mini Cooper S) have a turbocharger, which compresses the air before it...

G'day. Recently we conducted an experiment in the microwave engineering lab where we were tasked to measure power in, what's called, a Directional Coupler. Here you'll find much on it. My concern with the setup is that we took our measurements on a VSWR meter by noting off the db scale. So...

hi Just a little question. How does one calculate the power of a QCL by theory? Is there any free software that allows one to calculate the power of a inputted laser medium for a qcl? Thanks. Adrian

Homework Statement Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel's energy can be released quickly to accomplish a task that demands high power. An industrial flywheel has a 2.0 m diameter and a mass of 260 kg . Its maximum angular velocity...

Hello, I was given f(-4x)= 1/(1+4x), and I used the geometric series to find the power series representation of this function. I then took the limit of (-4x)^k by using ratio test. The answer is abs. value of x. So -1/4<x<1/4 I then plugged in those end points to the series going from k=0 to...

Homework Statement The Attempt at a Solution I have deliberately made several obvious steps, because I keep ending up here. However I have no idea what to do from here. I thought about the fact, that differential equations have the solution ##x = x_{HOM} + x_{Inhom}##, but the ##x_{HOM}##...

A cable of resistance 12 Ohm carries electric power from a generator producing 250 kilowatt at 10,000 volts. Calculate the current in the cable. Solution using P=VI I=25A but using P=I^2R 250000=I^2×12 I =500/root 12 Amps What is the reason for the different...

I'm currently in a undergrad level course of eletromagnetism and my professor found it useful to remember quickly of some relationships that we see in high scool, among them power waste. I got the formulas, since they're simple and are direct derivated from the definitions of electric current...

Hello, I have a question about calculating input power. Does the following formula work? Shaft Power (Supply) / Motor Efficiency? We are trying to calculate what an existing fan is using but do not have assess to site. We have the shaft power and motor efficiency from the manufacturers data...

Homework Statement For a power spectrum density fluctuations ##P(k) \propto k^n##, I need to find the scaling (with respect to ##a##) of the horizon wavenumber ##\frac{2\pi}{\chi_H}## in a matter dominated universe in terms of ##n##. ##\chi_H(a)## is the evolving particle horizon, in a flat...

as homework, I have to do the following exercise: Bremstrahlung emission : We are interested in ionized plasma of density ##n##, at temperature ##T## with ions of charge number ##Z##. 1. Explain the physical origin of bremstrahlung radiation 2. Represent the expected spectra (shape and...

Hello, I need the stopping power for a proton ion gun through Boron-11 sheet 1mm thick. I have the following table obtained from here: https://www-nds.iaea.org/stopping/stopping_hydr.html Where the unit is in 1-15*eV*cm2/atom: Then I calculated for 600keV protons at table 5.1eV*cm2/atom. I...

Is there a formula that I can use to calculate the HP a motor is actually making if all I have is amp draw? I am trying to size a gearbox, but the customer has no idea what torque is needed. All they know is the motor is drawing 5 amps when it spikes and 3.5 amps when it is running. I am...

I am currently working on a high power class E amplifier which will sit inside a metal enclosure. It is powered by two power supplies - both are isolated but one of the power supplies is mounted in the same enclosure. The power supply itself is in a metal case and that case is connected to...

Why can't we launch satellite by using electromagnet power?

Homework Statement Find an approximate expression for the ratio of the power densities at the principal maximum to that at the first secondary maximum on either side, in the Fraunhofer diffraction pattern of an N-slit multiple aperture. Assume that the slits are much narrower than their...

Hi, here I am again. This is also related to my previous threads. My question is: How do I calculate the power of generator in terms of speed(rpm) from a drive system (such as belt and chain drives)?

Dear forumers, I need a 50hz 250VAC power line filter for an EMI shielding faraday cage. The filter should work between 100khz and 20ghz, attenuation should be >=60dB between 1mhz - 5ghz. Regular power line EMI filters like this don't seem to go that high (only up to a few hundreds of mhz...

Hi Everyone! There is a type of CO2 laser cutter power meter on the market (Product link removed) The meter uses a block of black anodized aluminum bonded to the end of basically a mechanical meat thermometer, and has a zero adjustment on the back of the face to set the base temperature to...

Hello I'm trying to set up my gaming computer in my 2018 Kenworth T680 but having power issues. Both with the monitor and the tower. But mostly the monitor. I realize the power inverter is likely incompatible with monitor and tower PSU. I need a workaround. Issue: Monitor works interminitly for...

Say I have ##e^{2\pi i n}##, where ##n## is an integer. Then it's clear that ##(e^{2\pi i})^n = 1^n = 1##. However, what if replace ##n## with a rational number ##r##? It seems that by the same reasoning we should have that ##e^{2\pi i r} = (e^{2\pi i})^r = 1^r = 1##. But what if ##r=1/2## for...

Homework Statement Homework Equations P=V2/R For maximum power transfer, Rload=RThevenin The Attempt at a Solution I know the efficiency is 50% during maximum power transfer. So when all the sources are acting simultaneously and ( at the same time) R=Rth, maximum power will be dissipated in...

Homework Statement Suppose we are given the power series expansion ##f(x) = -\sum_{n=1}^{\infty} \frac{x^{n}}{n} ## which converges for |z|<1. What is the radius of convergence? Sum this serie and derive a power series expansion for the resulting function around -1/2, 1/2, 3/4 and 2. The...

Let's say you have a UPS 550 Watts (1100 VA). How much current or watts does the unit itself used? This is important when your source itself is limited by the wiring.. let's say all your computers total 500 Watts and the wiring is sized for roughly that.. Would the UPS draw more current or...

interested in efficiency metrics with regard to our base-load infrastructure... this information is not readily available. I think that renewable stuff has its place only after we make the most of our base plants with load shifting. The base plants exist, and they waste energy. I simply do not...

Unique Fingerprints of Alternatives to Inflation in the Primordial Power Spectrum "Massive fields in the primordial universe function as standard clocks and imprint clock signals in the density perturbations that directly records the scale factor of the primordial universe as a function of...

When to use ## V =-\int E ⋅ dl ## or ## V =\int E ⋅ dl ## ? When i use ## V =-\int E ⋅ dl ##. i can not show that P = IV because ##\frac{ln \frac{b}{a}}{ln \frac{a}{b}} ≠ 1## But the solution use ## V =\int E ⋅ dl ## I'm concerned about using "minus" .

Hello, so I'm rather new here and I was wondering when I plug a USB device into an AC adapter, such as a phone how does it output exactly 5.2V and 2A? I'm aware that it goes through a transformer and rectifier but I heard somewhere that when the voltage is reduced the current is increased? Does...

To be more specific, if i have to heat water 300l of water in one hour. What should the power of a heating coil?

Homework Statement A voltage of V = V_0 sin(\omega t) is applied to an inductor. Find an expression for the current and hence the power. Homework Equations I have used the equation: V = -L \frac{di}{dt} and for power: P = IV The Attempt at a Solution I tried to find I(t) by integrating...