Questions tagged [math]

Math or Mathematics is the abstract study of topics such as quantity (numbers), structure, space, and change.

Mathematics is the abstract study of topics such as quantity (numbers), structure, space, and change. There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics.

Concepts in engineering are generally analyzed using mathematical models. Any given concept or component may have more than one applicable model, with each having varying degrees of precision or domains of application.

Processes can generally be divided into continuous-domain and discrete-domain. Continuous-domain processes can be modeled using differential equations, while discrete-domain processes can be modeled using difference equations. In principle, a complete mathematical model of a system allows one to compute any past or future state of the system. However, in the case of systems which exhibit a mixture of continuous and discrete dynamics, no single set of equations can provide a complete mathematical model.

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Why are complex numbers used in electrical engineering?

When I was in high school, I asked a physics teacher "Why do we use complex to calculate stuff with electricity?" (something along that line) and he said "Because it just happens to work" without further details on WHY it works. I'm in CS/IT and am…
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Converting a summation to an integration

I've seen it done a few times, it's always roughly apparent that "oh yeah, okay, they've dropped this, pulled this there, yeah, okay, kind of convincing" - but I've never why or how to do it for myself. I probably don't understand it enough to be…
OJFord
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Calculating run time for a device with variable current draw

I recently built a small microcontroller-based project for a friend that consumed different amounts of current at different times. I wanted to calculate the run time for a given battery type (but discovered the area of my brain that used to know…
JYelton
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Calculating dBFs from RSSI

I have RSSI calculated as vector magnitude. $$ RSSI = \sqrt{I^{2}+Q^{2}} $$ I and Q are 12bit values from ADC. Is there a way to convert RSSI to dBFs and how it is done?
gillian
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How can I determine the peak power consumption of my office

how can I determine the theoretical peak power cost per hour for my computer? What is the formula I can use to calculate this? Do I need to know amperage? My current cost per hour is $0.11/kWh 1200W power supply in my computer 2 - 110W 24"…
NDBoost
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Complex Numbers, Phasor Notation, and Eulers Identity

On Page 30 in the Art Of Electronics (2nd Edition). The two images below describe the conservation of Sinusoidal signals to a complex representation and back. I am perfectly ok with the first image. The next image has me stumped. In particular,…
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Complex multiplication identity

From my EM theory book: I have the solution for this problem, but I don't even understand the first step. How does \$V = r + jx \implies v(t) = rcos(wt) - xsin(wt) \$??
Austin
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Do not understand how to multiply exponential values

Show how the current i_3=7e^(jπ/4) can be multiplied by Z_3 (in exponential form) to give the voltage through the branch. Calculate using exponential values, then convert to polar so show value and phase of the voltage. \$Z_3=15\angle-60^\circ =…
Jason
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math conjugate problem

why is the equation on the left equals the right? know would I derive it?
uri leids
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Differential amplifier solving equations for iDS

In large signal analysis of differential amplifier there are some equations to determine iDS. If we simplify it looks like that : \$ \large 2x^2+2kx+k^2-2\frac{l}{m}=o\$ Is there an easy way to solve these kind of equations. What should one study…
user211748
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Art Of Electronics - 2nd Edition - Absolute Value of a Complex Number - Math

In this section, I am struggling with the line Abs(V) * Abs(I) = V0^2 / [blah blah] I am not seeing how the math simplifies to that term. After looking up the absolute value of a complex number, and seeing that it is basically Pythagoras theorem…
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Art Of Electronics Second Edition - Math Question - Complex Number Current Calculation

How does the author obtain the expression I is approximately equal to .059sin(wt) In the beginning of the book, 30 pages back, the author stated that V was equal to Asin(wt) (if you ignore phase), why is V now equal to Acos(wt)? More importantly…
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how to calculate exp(x)

Could someone explain me how to calculate "exp"? Basically I have to calculate intrinsic density for silicon at T = 200K $$n_i=(N_cN_v)^{1/2}exp(-\frac{E_G}{2E_T})[cm^{-3}]$$ $$\sqrt{N_c…
Tensio
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Is \$j\sin(\omega t)\$ just \$\sin(\omega t+90)\$?

If so, then the Euler formula is much less aesthetic in my view... And, in IQ modulation, is the Q signal \$j\sin(\omega t)\$, or \$\sin(\omega t)\$?