per unit Definition and 105 Threads

Help please...Transmission line parameters in per unit hello there I'm trying to work on a program that converts electrical quantities of transmission line ( R , L , and C ) into per unit system using Matlab the thing is that I'm finding difficulties with the formulas , how I can obtain...

I was reading a link i found here on physicsforums called "The relativistic rocket". There was lots of calculations of the required fuel for certain distances and such. However, I understand that time→0 when our velocity v→c. And that will mean we travel a larger distance for a shorter...

Homework Statement Starting with: G = \frac{I}{V}= \frac{-\int_{s}\sigma\mathbf{E}\cdot d\boldsymbol{s}}{-\int_{l}\boldsymbol{E}\cdot d\boldsymbol{l}} Derive the conductance per unit length, G', of a coaxial cable by assuming a line charge of \rho_{l} on the center conductor...

1) I'm not sure how to solve this question A 20MVA induction motor connected at 13.8kV draws a load current of 1.0 p.u, 0.85 power factor lag. Calculate the rated load current in Amps and the real power and reactive power drawn by the motor. Express these quantities in per unit form using...

Homework Statement Two parallel whires, separated by a distance D (midpoint distance), are charged with a current density L (each whire has a radius R). If the whires have the potential +/- X Volts, what is the force per unit length between them? Homework Equations B = μ0*I /(2πr) is...

Homework Statement I don't know if this is a physics problem per se but its from physics class. So we were supposed to pick out a solar panel and figure out what is the cost per unit of energy for this form of solar energy? I know where supposed to use the data sheet for the panel that we...

Homework Statement Ok so using the standard equation v = Sqrt(T/Mu) I want to find Mu as a gradient for the first fundamental. I've made it into F x lambda = sqrt(T/Mu) Then f x 2l = sqrt(T/Mu) Then f= sqrt(T/4l^2 Mu) As I'm having the tension held by a mass suspended over a pulley. f=...

Dear all, My aim is to get the density of states (DOS) per unit area for monolayer (bilayer) graphene. I have done this using mathematica. I have set a sampling k grid with 22500 points and computed the expression: DOS=(1/Nk)*Ʃ δ(E-Ek) where the sum is over the k points in the reciprocal...

Homework Statement A cylinder rotating uniformly about the x' axis of S' will seem twisted when observed instantaneously in S, where it not only rotates but also travels forward. If the angular speed of the cylinder in S' is ω, prove that in S the twist per unit length is yωv/c(squared)...

Homework Statement long solenoid of n turns per unit length is wound upon a cylindrical core of radius a and relative permeability. The current I through the solenoid is increasing with time t at a constant rate. Obtain expression for the rate of increase of stored energy per unit length...

Why is the number of charge carriers per unit volume is inversely proportional to resistance?If there is more charges carrier, it doesn't increase the collision between free electron which causes in increase of resistance?sorry for my unclear concept of Electricity circuit.I hope there will be...

Homework Statement Consider a small portion (area=A) of the inside wall of a container full of gas. Show that the number of molecules colliding with this surface in a time interval Δt is PAΔt/(2mvx avg), where P is the pressure, m is the average molecular mass, and vx avg is the average x...

I learned Potential but could not understand what Potential Difference is. Some define it as Work Done per unit charge. I am confused what per unit charge is. Does that mean electrons or protons ? As much as I know, electric current is the flow of negatively charged electrons to the positive...

Hi, exam question: My doubts start where it comes up with: S=75(0.8-j0.6) and Vr = 0.97 p.u. Its easy to determine that 75 comes from 60/0.8, but where is the part in the brackets coming from ? Also how was the 0.97 determined ? Thanks in advance.

dear PF.. what is the Bernoulli equation in terms of energy per unit volume the equation include the 1) static pressure 2) hydrostatic pressure 3) dynamic pressure 4) stagnation pressure

Homework Statement In the special theory of relativity the mass of a particle moving at speed v is given by the expression m/(1-(v2/c2)) where m is the mass at rest and c is the speed of light. At what rate is the mass of the particle changing when the speed of the particle is (1/2)c and is...

B=Boexp[-(kz-ωt)2)] i(hat) Calculate the electric field associated with the above magnetic field pulse. Calculate the Poynting vector for the EM field and the total energy per unit area. Use Maxwell's equations in vacuum and assume electric potential is zero. Homework Equations...

Homework Statement Compute the maximum amount of water vapor per unit volume that air can hold at the surface, where Ts = 288 K, and at a height of 10 km where T = 220 K. Express your answers in kg m-3. Homework Equations e_{s}=Ae^{\beta T} e=\rho _{v}R_{v}T The Attempt at a...

I need to obtain the mass per unit length. Is it as simple as just mass / length?

Homework Statement A sample of dry air has initial pressure p1 = 1000 hPa and temperature T1 = 300k. It undergoes a process that takes it to a new pressure p2 = 500 hPa with unchanged temperature T2 = T1. Compute the mechanical work per unit mass performed by the sample under the following...

I am just trying to understand exactly what luminosity per unit frequency is. I know that luminosity (L = 4PI(r2)(flux)) is amount of energy per unit time, but not sure what it means when it is also per unit frequency. The question has a cosmic source of 100 solar luminosity, all emitted...

Homework Statement The frequency of a vibrating string is set to 15, 20, 25, 30, or 35 Hz and the length needed to attain a standing wave (mode 1) is recorded. A graph of frequency versus 1/L is recorded. Calculate the mass per unit length of the string. The resulting graph has the...

Why is the number of electrons per unit volume , n fixed in a conductor regardless of the temperature while its not in semiconductors ??

Homework Statement Two wires have current both running in the positive x direction as shown in the diagram with I1 = 13.9 amps and I2 = 4.5 amps. They are separated by a distance of d = 4.7 meters. A third wire with I3 = 10 amps is placed somewhere between the two wires with current running...

Homework Statement The coaxial cable from a television or other device has an inner conductor with diameter of 1 mm and the shield of diameter 5 mm. Assume a plausible value for the dielectric constant (3 ≤ κ ≤ 5) of the dielectric separating the two conductors and calculate the capacitance...

Homework Statement A guitar's E-string has length 65 cm and is stretched to a tension of 85 N. It vibrates at a fundamental frequency of 329.79 Hz. Determine the mass per unit length of the string. 1Your answer is in kg/m Homework Equations (mass per unit length) = (tension) /...

1. Homework Statement [/b] Suppose in the figure that the four identical currents i = 13 A, into or out of the page as shown, form a square of side 64 cm. What is the force per unit length (magnitude and direction) on the wire in the bottom left hand corner? (N/m) Take the positive y direction...

Homework Statement You are planning to install a home video studio. A very important piece of information is missing from the specifications. You must find the capacitance per unit length for a coaxial cable. The cable has an inner radius of 2.0mm and an outer conductor 4.0mm in radius...

Hi, I am trying to calculate how many electrons I need to confine in one cubic centimeter to make the pressure on the "walls" 1psi. I've tried the equation for the repulsion of two charges, but we're talking about trillions of electrons here and they're all pushing on each other however...

1. Homework Statement [/b] You are planning to install a home video studio. A very important piece of information is missing from the specifications. You must find the capacitance per unit length for a coaxial cable. The cable has an inner radius of 1.1 {\rm mm} and an outer conductor 3.1 {\rm...

How is the absorption coefficient per unit path length determined for excitation sites in a host crystal with an excitation site density of N and a bandgap of the excitation site equal to the photon energy? What I am trying to determine is how many photons will be absorbed for a given length.

Homework Statement A 3-phase generator rated 100 MVA, 13.2 kV, X = 20% is connected through a Δ/Y transformer to a transmission line whose series reactance is 40 ohms per phase. Assume that the base values in the line circuit are 200 MVA and 115 kV. Find the generator and transformer...

Homework Statement Two long straight wires in the xy plane are parallel to the x axis. One wire is at y = −8 cm and the other wire is at y = 8 cm. The current in each wire is 24 A and the currents are in the negative x direction. The permeability of free space is 4 π × 10−7 T · m/A...

Homework Statement The E field in an EM wave has a peak of 22.8 mV/m. What is the average rate at which this wave carries energy across unit area per unit time? Homework Equations S = e_0*c*E^2 The Attempt at a Solution where e_0 = 8.85*10^-12 c = 3*10^8 E = 0.0228 V/m S =...

i am a non physics or math major taking a 'physics of sound and music' course that deals with different wave forms. i am enjoying the class very much (more than i thought i would!) but am having trouble with the math, as the last math class i took was pre-calculus my junior year of high school...

Homework Statement A very long uniform line of charge has charge per unit length 4.82 uC/m and lies along the x-axis. A second long uniform line of charge has charge per unit length -2.46 uC/m and is parallel to the x-axis at y1= 0.418 1-)What is the magnitude of the net electric field at...

Homework Statement A packed bundle of 100 long, straight, insulated wires forms a cylinder of radius R = 0.600 cm. If each wire carries 4.50 A, what are the magnitude and direction of the magnetic force per unit length acting on a wire located 0.200 cm from the center of the bundle?Homework...

Homework Statement Basically, the problem states that a cavity at temperature T is emitting EM waves isotropically in all directions (with frequency distribution of Planck's Law). If the time averaged density is <e>, find the value of d<S>/dw where w is the solid angle and the quantity is the...

"flux per unit projected area per unit solid angle," L = \frac{\partial \Phi}{\partial \left(cos \Theta \right) \ \partial \Omega} What is this quantity? I mean, I know it's "flux per unit projected area per unit solid angle," how does the math work? I know it's not \frac{\partial...

Homework Statement Some electrical appliances are used with long cables to connect to them to the electrical supply. State and explain 2 reasons why these cables should have a low resistance per unit length. The Attempt at a Solution well for the long cables, a low resistance per...

[SOLVED] Finding mass per unit length for stretched strng given tension? A transverse wave on a stretched string under Tension = 5N is defined by the equation: y(x,t) = 0.1cos(2pi/5(x - 10t) Find: a) amplitude = 0.1 m b) wavelength = 0.4 m c) angular frequency = 4 rad/s d)...

[SOLVED] Same string, different mass per unit length, what's the wavelength? *oddly I can't edit the original title? Homework Statement A string is made of two materials of different mass per unit length. On the left side of the string, the mpu is given as well as its wavelength. On the...

Homework Statement The atmostspheric electric fields at heights of 100m and 1000m above the surface of the eartg are 110 v/m and 25 v/m respectively and are directed downwards. Evaluate the averge electric charge per unit volume in the atmostsphere between these heights. Express your result...

OK. In my book it says that for "any point" the Electric Field Magnitude for a Infinite sheet of charge with uniform charge per unit area is \frac{\sigma}{2\epsilon_{0}} , and for a wire of infinite length the Electric Field Magnitude is E = \frac{\lambda}{2\pi\epsilon_{0}r} where r is the...

[SOLVED] Mass per Unit Length of Violin Strings Homework Statement Each string on a violin is tuned to a frequency 1.5 times that of its neighbor. If all the strings are to be placed under the same tension, what must be the mass per unit length of each string relative to that of the lowest...

Hi there. In my homework, I had to calculate the variation of the pressure with the altitude for a classical gas. I know that I should calculate the density of particles per volume element. I found this pdf on the net (http://cannoli.mps.ohio-state.edu/phy847/phy847-p2.pdf) . If you see...

Sir, A man covers his body with a blanket of thickness 4 mm. His temperature is 37 degree Celsius and that of the atmosphere is 27 degree Celsius. If the coefficient of thermal conductivity of wool is 1.2 x 10^(-5) W/m.K , what is the heat lost per hour per square meter area? I solved it...

I'm attempting to answer these thermodynamic quesions about entropy. It's been years since my last thermo course so knowledge is cloudy. If I'm incorrect or missiong relevant answers, please help. a. If ds = 0, what can you say about the process? b. If ds < 0, what can you say about the...

'A radioactive element has a 0.5 probability of decaying to a more stable element after a particular time-span T. What is the instantaneous decay rate per unit volume? In other words determine a general expression for the number of decay events occurring per unit volume between t=t1 and t=t2...

a) Find the total power radiated into space by the Sun, assuming it to be a perfect emitter at T = 5690 K. The Sun's radius is 7.0 108 m. (b) From this, determine the power per unit area arriving at the Earth, 1.5 X 10^11 m away. the formula for radiation is Power = (emittance...