# Search results

1. ### A more efficient transformer

I have been reading about mag-amps which gave me an idea for a more efficient transformer. So the core is in the shape of a square or rectangle with a center piece dividing it into two. The construction of the outer core is larger (less reluctance) than the middle leg (greater reluctance). The...
2. ### Capacitor Voltage

Hi, I am trying to figure out the peak voltage across a capacitor when charged by 1/2 wave rectified AC. The formula for instantaneous voltage is : Vc=Vs(1-e-t/RC) where: Vc=Capacitor voltage, Vs=Source Voltage, t=time RC = the capacitor time constant So I thought I could integrate with...
3. ### Energy in a capacitor

This post is inspired by a lesson on the allaboutcircuits education website. In chapter 15 of Direct Current there is a heading "Inductors and Calculus" - https://www.allaboutcircuits.com/textbook/direct-current/chpt-15/inductors-and-calculus/ At the bottom of the topic there is a circuit...
4. ### Plasma Multipactor

I have been reading a patent by Gene Meeks of a plasma multipactor. Meeks was the right hand man of Philo Farnsworth the "father of television" and worked with him on the 'fusor' - a small nuclear fusion device. Meeks's multipactor appears to be a self sustaining over unity power device...
5. ### Independent Component Analysis vs Single Spectrum Analysis

Homework Statement Hello, I have implemented single spectrum analysis and independent component analysis against a time series (in this case the euro foreign exchange) as a smoothing indicator. The ssa algorithm I purchased from: Caterpillar-SSA - http://www.gistatgroup.com/cat/programs.html...
6. ### Single Channel Blind Source Seperation

Homework Statement I am trying to figure out how to do independent component analysis on a single stream of time series data. The ica algorithm comes as part of the it++ package however it is necessary to perform some preprocessing on the time series data as ica works on the premise that the...

10. ### Derivative of Dirac Delta - Fourier Transform - Time Differentitation Property

Homework Statement I am using the time differentiation property to find the fourier transform of the following function: Homework Equations f(t)=2r(t)-2r(t-1)-2u(t-2) The Attempt at a Solution f'(t)=2u(t)-2u(t-1)-2δ(t-2) f''(t)=2δ(t)-2δ(t-1)-??????? Can somebody explain what...
11. ### Properties of the Fourier Transform - Time Differentitation

Homework Statement This is copied from a book: \eqalign{ & {\rm{Time Differentitation}} \cr & {\rm{Given that: }}F(\omega ) = F\left[ {f(t)} \right] \cr & F\left[ {f'(t)} \right] = jwF(\omega ) \cr & {\rm{Proof:}} \cr & f(t) = {F^{ - 1}}\left[ {F\left( \omega \right)}...
12. ### Difference between and odd symmetrical function and 1/2 wave odd symmetrical function

Homework Statement The book defines a 1/2 wave odd symmetrical function as each 1/2 cycle is a mirror image of the next. \begin{array}{l} {a_0} = 0 \\ {a_n} = {\textstyle{4 \over T}}\int_0^{{\raise0.5ex\hbox{$T$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{\$\scriptstyle...
13. ### [cos nt - n.sin nt] rewrite as [cos (nt + tan^-1 n)]

Homework Statement I am working through an example in fourier analysis and the author has rewritten [cos nt - n*sin nt] as [cos (nt + tan^-1 n)]. Can somebody show how he does this? ie. the steps involved. Homework Equations The Attempt at a Solution
14. ### Laplace Transform

Homework Statement Is there an easier way of solving this rather than doing the integral? Find the laplace transform of: t{e^{ - t}}u(t - 1) Homework Equations The Attempt at a Solution \int_1^\infty {t{e^{ - t}}} {e^{ - st}}dt = \int_1^\infty {t{e^{ - t(1 + s)}}} dt =...
15. ### Derivative of an Integral

Homework Statement F is an antiderivative of f, so F’=f. \begin{array}{l} \int_{g(x)}^{h(x)} {f(t)\,dt} = F\left( {h\left( x \right)} \right) - F\left( {g\left( x \right)} \right) \\ \frac{d}{{dx}}\int_{g(x)}^{h(x)} {f(t)\,dt} = F'\left( {h\left( x \right)} \right)h'\left( x \right) -...
16. ### Energy in AC circuits

Given that: E = hν where E = energy of a photon h = Planck's constant = 6.626 x 10-34 J·s ν = frequency Why is it that the energy (electromagnetic waves) in AC electrical circuits does not include frequency as part of the formula? eg. \begin{array}{l} P =...
17. ### Charging a capacitor with AC voltage

Homework Statement Can somebody explain how it is possible to charge a capacitor using ac voltage? The way I see it is the capacitor wouldn't have time to charge as the voltage is constantly switching. In the case of 60Hz - 120 times a second. I seen a schematic of a tesla coil where the...
18. ### Charging a capacitor in a tesla coil

Can somebody explain how it is possible to charge a capacitor using ac voltage? The way I see it is the capacitor wouldn't have time to charge as the voltage is constantly switching. In the case of 60Hz - 120 times a second. I have attached a schematic of a tesla coil which is how I come to...
19. ### Charging by Inductance

http://www.youtube.com/watch?v=o0hXYfvnND0 What would happen if the ground was kept in place and the positively charged rod was constantly moved to and away from the electroscope? Would we not have ac current between the earth and the electroscope? Replace The electroscope with a capacitor...
20. ### Resonate Frequency of Bandpass Filter

Homework Statement See attached. Can somebody explain how the resonant frequency w0=1/RC. I worked it out by setting imaginary Z(s)=0. The answer I get is j√2 which is obviously wrong. Is it wrong to calculate the resonant frequency in this manner in this case? Homework Equations...
21. ### Engineering Resonate Frequency of Parallel RLC Circuit

Homework Statement Determine the resonant frequency of the circuit in Fig 14.28 (See attached) Homework Equations \begin{array}{l} {\rm{How is }} \to {\omega _0}0.1 - \frac{{2{\omega _0}}}{{4 + 4\omega _0^2}} \\ {\rm{derived from }} \to j{\omega _0}0.1 + \frac{{2 - j{\omega...
22. ### How do I solve this equation for x?

Can somebody point me in the right direction with this? \begin{array}{l} \sqrt {{R^2} + {{\left( {xL - {\textstyle{1 \over {xC}}}} \right)}^2}} = \sqrt 2 R \\ {R^2} + {\left( {xL - {\textstyle{1 \over {xC}}}} \right)^2} = 2{R^2} \\ xL - {\textstyle{1 \over {xC}}} = R\sqrt {2 - 1} \\...
23. ### Ideal Transformer

Homework Statement See attached Homework Equations V2/V1=I1/I2=n n=2 The Attempt at a Solution \begin{array}{l} {\rm{Mesh 1: }} & 4{I_1} + {V_1} = 60 \\ {\rm{Mesh 2:}} & 10{I_2} - {V_2} - 2{I_3} = 0 \\ {\rm{Mesh 3:}} & - 2{I_2} + 10{I_3} + {V_2} - {V_1} = 0 \\ {I_1} =...
24. ### Completing the square 2 variables

Homework Statement Ax^{2}+By^{2}-Mxy Capitals are constants. The equation (one like it) is in a book I am reading where the author procedes to complete the square. He does it in one line without showing the procedure and I am completely baffled. Homework Equations The Attempt...
25. ### Mutual Inductance Problem

Homework Statement See attached. Homework Equations The Attempt at a Solution (5+j8)I1-j6I2-j3I2-j3I1*2=magnitude(12) degrees (60) (5+j2)I1-j9I2=magnitude(12) degrees (60) j2I2-j6I1-j3I1=0 -j9I1+j2I2=0 I put these equations into mathematics software and get the answers...
26. ### Engineering Line Current for 30kW 3 phase motor

Homework Statement Calculate the line current required for a 30kW 3 phase motor having a power factor of 0.85 lagging if it is connected to a balanced source with a line voltage of 440V. Homework Equations P=√3Vl*IlCos ∅ Il=\frac{P}{√3VlCos ∅} P=Average Power Il=Line Current Vl=Line Voltage...
27. ### Power Factor

Homework Statement I understand power factor is defined as (average power)/(apparent power) or cos(theta v - theta i) where theta v = load voltage and theta i = load current. Also the power factor angle is equal to the load impedance. I don't understand how the 2 definitions of power...
28. ### Mathematics Software

Is anybody aware of a free or at least inexpensive mathematics software package which allows the calculation of linear equations involving complex numbers? Hopefully relatively easy to use.
29. ### Mathematics Software

Is anybody aware of a free or at least inexpensive mathematics software package which allows the calculation of linear equations involving complex numbers? Hopefully relatively easy to use. Woops - I posted this in the wrong place. Please ignore.
30. ### Phase Shifter

Homework Statement Can somebody explain why the voltage across the capacitor (v0) lags vi? Homework Equations The Attempt at a Solution Homework Statement Homework Equations The Attempt at a Solution