Power Definition and 998 Threads

Hi I have a problem dealing with rpm power and torque. I have a motor powering a gearbox which has a 20:1 ratio. The power and rpm are not an issue so i have not looked at those figures but the motor produces 240Nm of torque. Since it is a 20:1 gearbox, i have assumed the torque is 20 times...

Homework Statement (Is the image read-able now? ) The fig 1 shows the relationship between voltage and current when voltage is applied to a certain light bulb. Next, in fig 2, the bulb is connected in series with a 12-V battery and a 5 ohm resistor. Question : what is the amount of power...

Homework Statement Two 15Ω coffee-makers are connected to a 120V power supply for two hours a day each. Find the power and energy. Homework Equations P=V2/R ΔE=PΔt The Attempt at a Solution I am assuming, since there are two coffee-makers connected to one 120V power supply, that: P = V2/R =...

Homework Statement Homework EquationsThe Attempt at a Solution Power dissipated in the 2 Ohms resistor will be maximum when current is maximum .This will occur when total resistance is minimum . If I think logically then I do get the right answer . But on trying to arrive at the result...

Hi there again, I am trying to correctly calculate the tractive effort pf a train, currently i do this: Power/speedMpS = TractiveEffort I got that from here. But it doesn't provide realistic values, so i am wondering, what is the correct way of calculating tractive effort of a train? Thanks

How to calculate torque and power at 'drive wheel' with following inputs and also requirement shown in below picture- a. Gear ratio, 1: 6 b. Attached 10Kg weight for bigger wheel to make as a crank wheel and diameter is 30inch. c. Bigger wheel: Consider 180 degree is freely rotates(due to 10kg...

How does this version of the power equation relate to physical situations? Does the value you get give you an instantaneous power? Or is the velocity to be taken as the average velocity (an actual displacement over time)?

Hi there again, I have been wondering why train simulators(and trains themself) have a kW specification, AND a maximum force indication. If I would calculate the speed of a train using some formula, then where is the power value used for? Does it have something to do? Or is only the maximum...

Homework Statement apparently your effective power is V_maxI_max * cos(x) where x is the phase angle. So I must consider only real power Homework Equations power = VI current = I sin(wt) The Attempt at a Solution Let impedence be = e^ix . I'll write current as Ie^i(wt) consideronly the real...

Dear members, The unit of stopping power is given as Mev/cm in many sources. It is easy to comprehend this unit.The mass stopping power, which is the total energy lost per path length by a charged particle, is defined as the division of MeV/cm to the density of investigated material, g/cm3, and...

This is a simple problem from a textbook I am reading, and everything below is written word by word and sign by sign from said textbook. Formulas given in the book just don't give the result authors claim they do: Homework Statement An input of 1 W produces a SPL of 115 dB at 1 m. What is the...

Any clue to to show that it is 10kW? Please tell me where i went wrong and thank you. I tried and i just couldn't figure it out.

Homework Statement http://www.chegg.com/homework-help/questions-and-answers/interconnection-fig-p25-valid-find-total-power-developed-circuit-interconnection-valid-exp-q22345911 It asks if the circuit is valid, which I assume it is. It asks for the power developed[/B]Homework Equations I tried...

Homework Statement Hi, So I'm taking a communications module and we are being introduced to Energy Signals and Power Signals. Now in the notes, it starts off the chapter by saying "Suppose a signal x(t) is a real signal" and then it says The instantaneous power in x(t) is given by x^2(t)...

Hi all I am studying RF amplifiers data sheets and there is some confusion i am facing in its specifications. One such amplifier claims Power Output at 50 ohm load with 20% duty cycle to be 2 KW. However, the minimum gain it specifies is 63 dB and maximum input it claims to be 10 dBm (around...

I tried yesterday with the gyro and did not make myself clear. So let me try with a windmill, please. I look at a windmill and I see the blades are spinning. Thus, the shaft axis has an angular velocity. I can ballpark and check the angular velocity with my eyes. I want a ballpark...

Say I have a disk spinning in a buoy. Let me say the spin axis is vertical to the flat surface of the buoy (or sea if there were no waves). Now along comes a wave (that will induce a "precession" of the disk/buoy. The axis of this precession is from "starboard to port." This would induce...

Homework Statement A 4.0 Watt toy motor is connected to a secondary circuit of a transformer with 60 loops and a current of 0.10 A. The primary voltage is 120 V Homework Equations Vp / Vs = Ip / Is Ip = Pp / Vp[/B]The Attempt at a Solution 1. [/B]Vp / Vs = Ip / Is 120 V / 40...

Homework Statement Homework Equations I think it should be A for 1st and B for 2nd Shunt capacitor is used to improve power factor by giving reactive power to line. Series capacitor is used to improve efficiency of line as it nullifies effect of line inductance. And for 2nd Q proportional to...

Homework Statement It's a solved problem but I don't understand why is there no 30 degree lag from line voltage to lead voltage. Homework Equations Phase voltage = Line Voltage / 1.732 and there is 30 degree lag So shouldn't Ir be at angle 150 degrees.The Attempt at a Solution In Y line and...

Power is measured in watts and lightbulbs are rated in watts. P = W/t and W = Fd What is being displaced? electrical current?

Homework Statement A loaded elevator acge has a mass of 1500kg and a countermass of 1000kg. The cage is accelerated with 2m/s² to 1,4m/s and lifted to a height of 15m and stops at stand still. The inertia of the motor or the radius of the cablewheel is NOT given. The steady state speed of the...

Homework Statement w = 1 rad/s power factor is 0.8 lag Homework Equations Using Phasor we can do The Attempt at a Solution Since pf = 0.8 lag. I source lags V source by 36.87 degrees. Vc is voltage across Capacitor = Voltage across ( Resistor + inductor) Solving this I get C = 0.5 But book...

To illustrate my problem say I have the following table: Option, x , y A , 25 , 30 B , 5 , 12 C , 3 , 9 D, 12, 13 I want to create a graph of every possible combination in the set where the x values are added and the y values are added. For example say it was...

Homework Statement Energy released is 5.6MeV, 5kW is produced, Half life = 87.7 years for Uranium Need to find how many kg you need to produced that much power. Homework Equations E = Pt, Q = (mass defect) * 931.5MeV/c^2 The Attempt at a Solution I solved for the energy released to be...

Hi folks, I'm currently working on the design of a triplex plunger pump. I have conducted an investigation into the loading of the pump at maximum operating pressure using an analytical method (free body diagrams) and using rigid body dynamics to validate. In both analyses the pump has been...

Hi All, [This thread has been re-started to accommodate modification of the project for the benefit of anyone that isn't a qualified Professional. Specifically the use of a Low Voltage isolated Source.] I want to get the opinion of people with more experience than me, regarding a project I was...

Is it true that AC synchronous motors (the ones with the DC slip rings and excitation current running into rotor poles) have a power factor of 1.0 when they run in synchronous mode? Would that be because with sufficient rotor DC current he rotating AC magnetic field is precisely counterbalanced...

Hey! :o We have \begin{equation*}A:=\begin{pmatrix}-5.7 & -61.1 & -32.9 \\ 0.8 & 11.9 & 7.1 \\ -1.1 & -11.8 & -7.2\end{pmatrix} \ \text{ and } \ z^{(0)}:=\begin{pmatrix}1\\ 1 \\ 1\end{pmatrix}\end{equation*} I want to approximate the biggest (in absolute value) eigenvalue of $A$ with the...

How should power be calculated in a situation where distance and time are both given, as well as mass. At first, I was thinking of just using W=Fx (force as mass x 9.8) to solve for work, and then I would take the solution for work and put it into P=wt. Does this make sense? That's my best...

Hi, Forgive me for this trivial question. I am confused. Let's say I have a gyroscopic device in which the rotor is set to spin at a prescribed angular velocity. Next, put it on an ocean surface in which the ocean waves induce a precession. These two rotations, then induce a moment (induce a...

Homework Statement Maximum power is transferred to variable load when: 1) RL = Rs 2) RL not equal to 0. and Rs = 0 3) RL = 0 and Rs not equal to 0 4) RL = Rs/2 Homework Equations Maximum power theorem RL = Rs The Attempt at a Solution But if Rs = 0, then current is maximum, so load get...

During the early development of nuclear power many utilities were concerned that the United States federal government would create an "Atomic TVA" and crowd them out. As a result the plutonium production reactors in the United States didn't have steam turbines to generate electricity from the...

I was recently having a discussion about magnetic fields outside of a shielded power cable. My understanding up to this point was shielded cables only shields electric fields and not magnetic fields which are associated with current flow inside a cable. For the shielding to shield magnetic...

Homework Statement Homework Equations I think both A and C are right answers. The Attempt at a Solution 1 condition is pu Z(leakage) must be same on respective KVA rating for load sharing. Now: Zpu = Z(actual)/Z(base) ----equation 1 For Zpu of both transformers to be same, the right side...

My class just started the Energy unit and I would like to make sure my answers are correct to our HW questions. I am in high school Physics. Thanks. 1. Homework Statement A student lifts their 100N book-bag 1meter in order to put it on. How much work did the student do in lifting the book-bag...

Homework Statement There are three problems: 1. How much power is required to lift a 10.00 kg barbell at a speed of 3.0 m/s? 2.What is the average power supplied by a 70.0 kg firefighter climbing up a ladder in 10.0 s? 3. A man pulls a wagon with a force directed 22.0˚ above the horizontal...

Hi, I keep reading in multiple sources that amplifier output can be given by Vout = a0 + a1v(t) + a2v2(t) + a3v3(t) + ... + anvn(t) I've checked in three of my textbooks and there is not a clear definition (its often just stated) why this equation is used and why it works. I am not looking...

Homework Statement I have included the problems attached below. I have looked at a recent post and the equations made sense to me but I am very new to 3 phase systems basically know only what I have learned from trying to answer my questions. i feel my attempt is wrong from what I have seen...

Homework Statement I am having difficulty understanding the conversion between power and rotation at the engine and at the wheel. Can you please state which parts are right and wrong, and why please as I think I've spent that long on researching I've confused myself with too much information...

Homework Statement Homework EquationsThe Attempt at a Solution Taking change in the kinetic energy per unit time as power, P = ## \frac {d W}{dt} = \frac {d K}{dt} = \frac 1 2 \frac { dm} {dt} v^2 = 36.75 ## watt...(1) ## P = \vec F \cdot \vec v = \frac{ dm} {dt} \vec v \cdot \vec v =...

Hello, I have been looking to build a pmu similar to this device, it will be for domestic use. https://www.digikey.com/en/articles/techzone/2014/jan/low-cost-microcontroller-based-phasor-measurement-units-improve-smart-grid-reliability I am having a bit of trouble with the sampling part and...

Homework Statement Homework Equations I rms for triangular waveform = I(max)/ (1.732) R = V/I The Attempt at a Solution Since there is RLE load, current waveform is triangular. It is Source current is Average of I source. I used integration. Assumed Time period = 10 seconds. So T on = 5...

Homework Statement Homework Equations Solved example The Attempt at a Solution I think the red part should be (alpha/firing angle) = 180 - 45 Here since the angle is 45, it makes no difference if you do 90 + 45 or 180 - 45, but i think it should be 180 - 45. Am I right?

Homework Statement Homework Equations Since question says the current is always continous, so overlap is always there. So option B is incorrect. Also since firing angle is increased from 0 to 45, the overlap angle will reduce. So it'll be less than 45. So option A is incorrect. The Attempt...

I'm studying Newton Raphson Method in Load Flow Studies. Book has defined Jacobian Matrix and it's order as: N + Np - 1 N = Total Number of Buses Np = Number of P-Q Buses But in solved example they've used some other formula. I'm not sure if it's right. Shouldn't order be: N + Np - 1 N = 40 Np...

We know that belt drives are limited in their max possible power rating and most high power/torque applications(trucks) use gear drives. I wanted to know the main factor that limits the power/torque rating of belts. Is it Frictional slip or Belt material? If the frictional slip could be...

Homework Statement Homework Equations If load is inductive current lags voltage. If load is capacitive voltage lags current The Attempt at a Solution Current lags voltage since wire is inductive. So IF1 lags VF1 and IF2 lags VF2 But book says answer is C Why should VF1 lag IF1? This will...

Greeting . how electrical energy can be power over time when electrical energy is actually potential energy . from a lot of sources (wiki ,study.com..) comes the information that electric energy is potential or kinetic energy in other sources is said to be electric power p x t so i am...

Hi, So my power system book has a diagram for zero sequence impedance. I cannot find the full form of ZPB. I googled it up but couldn't come across anything.