Questions tagged [formula-derivation]

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Polarization Derivation

Can how I can find the phi and theta unit vectors as described (Eq. 4a and 4b) in the following paper on antenna cross polarization? I thought the thetha and phi unit vectors were the same as those of ...
• 11
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Noise added by an amplifier when deriving Friis's formula

I have been asked to derive the equivalent noise factor for a cascaded system of two amplifiers. Here is the figure of the system (assuming a general configuration where $G_1$ and $G_2$ are ...
95 views

Optimal thin absorber of electromagnetic energy

I am a material engineer and have a question about a formula derivation regarding microwave absorption properties. I really cannot figure it out after days of trying. This should be simple for a ...
177 views

"Inverting op-amp" circuit calculations using the general feedback formula

I managed to derive the "non-inverting op-amp" circuit using equations from the general formula of negative feedback. Unfortunately, I could not calculate the "inverting op-amp" ...
• 329
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Example problem of induced emf in a 100 turn coil by a 100 turn coil which has 90kHz sin wave input voltage

Main Question: Let's say there are two coils each 100 turn and diameter 30 mm, And the second coil is perpendicular to the first coil's magnetic field (placed both coils next to each other; we can see ...
• 45
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Example problem of induced emf in a coil rotating in the earth's magnetic field

I just recently learned magnetism-coil-faraday's law and I want to do some real world problem solving. Question: Let's say a copper wire coil (20 mm dimeter (r=10 mm)) of 3 turns (N=3) is on the ...
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3k views

Current at 12 and 230 volts

I hope someone can help explain this: Say I have a 12 V 100 Ah battery and a heater that uses 1000 watts. At 12 V we'll get <...
• 157
475 views

Diode Power Dissipation

I am having trouble solving this PD question. I feel like it’s straight forward but I can’t seem to get the correct answer. I was curious if I could get help from the community. Question: A p-n diode ...
• 57
140 views

Active low pass filter is there any virtual ground point? If yes how can I derive?

I'm learning this MFB active LPF. My questions regarding this as follows: How to derive transfer function for this configuration? Is there concept of virtual ground exist? If yes can you explain ...
66 views

How do I calculate the Capacitance for an RC Timer to charge to ANY voltage?

We have the following simple circuit. simulate this circuit – Schematic created using CircuitLab A capacitor is being charged by an resistor of 100 ohms from a 5V power supply. Let's say I want ...
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168 views

Can Watt’s law be derived from the Ohm’s law without using calculus?

Unlike Ohm’s law Watt’s law is not a fundamental law of electronics, as it can be derived from other fundamental laws of electronics. In the derivation above (see the pic) I used definition of current ...
352 views

How to derive transistor input impedance?

Given the following circuit, When Ro is not infinite, from the book, ZB is given as, However, when it's infinite, the input impedance is easily obtained as the parallel combination of RB and β(re+RE)...
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365 views

How to derive equation for current from parallel batteries given internal resistance and load?

I'm studying DC circuits in physics right now and have come across this frustratingly unclear part of the textbook. Apparently, the current through a circuit given ideal emf, internal resistance, and ...
298 views

Forward diode depletion capacitance formula

Does anybody know the forward depletion capacitance formulas for diodes in spice models? Background: The capacitance of a diode in reverse direction usually is dominated by the depletion (or junction) ...
• 153
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Zero current assumption in star - delta transformations derivations

The formula used for star delta transformations are: $$R_A = \frac{R_{AB} R_{AC}}{R_{AB}+R_{AC}+R_{BC}}$$ and $$R_{AB} = \frac{R_AR_B + R_AR_C + R_BR_C}{R_C}$$ The normal way that these formulae ...
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Inconsistency of electrical loss function

We have a function to calculate electrical losses for resistances and it is that $$P = I^2 \cdot R$$ If we consider this formula, our teachers generally say that if you want to decrease the losses, ...
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1 vote
630 views

Deriving power formulas for transmission lines

I'm trying to derive formulas for active power ($P_s$) and reactive power ($Q_s$) at the sending end of a transmission line shown below: Where: $E_s$ and $E_r$ are voltage magnitudes $X$ is ...
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1 vote
887 views

Formula for calculating instantaneous power in pure inductive and pure capacitive circuit

According to the material provided by a faculty this is what the formulas were and how they were derived. According to the derivation we did in class, we were getting: P = -VrmsIrmssin 2ωt for pure ...
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1 vote
79 views

Can someone confirm my derivation of the generalized power law from Practical Electronics, 4th edition?

I dont know how to use LaTeX, so I used Mathcha and took a snip from there.
• 135
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Looking for a formula to calculate the resitance needed to make a proximity sensor shorter! RCWL-0516

I want to decrease the range of this cheap sensor dramatically from 5m to 5cm! Im not sure which equation I use to calculate this. I'm assuming but not sure if there is a bigger resister value that I ...
• 101
276 views

Overall Gain for Mixer Circuit

I am working on an audio mixer circuit for balanced studio gear. The circuit consists of two unity gain balanced line receivers (THAT1200), going into a pair of voltage dividers controlled by a shared ...
80 views

Transfer function : Determination [closed]

I have the below circuit, here, I have Is and Va are measurable quantities. Rc1..Rc4 and Rbd are unknown variables for which I intend to derive transfer function. I have flexibility of adding ...
• 121
291 views

How to derive the formula from this circuit?

This is the schematic to measure the $R_{iso}$. There is a switch, Q2 for the measurement. I need to find how to derive the $Y_{iso}$ from this circuit schematic. To find it out, I tried to use ...
1 vote
186 views

Transfer function : Complex network

For the attached circuit attached in LTspice spice, I am trying to find the transfer function interms of Rc1,Rc2,Rc3 and Rc4. For that I have switches which I configure to turn on/off and measure the ...
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45 views

1 vote