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Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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2answers
323 views

Wire 5 vibration motors on one switch

I am trying to run five vibration motors rated at 3.7 volts each on one switch. The power will come from a 12V, 40 Amp relay on my Jeep (SPOD). How can I wire the motors all together to turn on at one ...
0
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2answers
133 views

Why is diode D2 affected by the current of Vin and the choice of R1?

I was wondering why D2 will not always forward voltage drop .6 volts? Ground is at 0. What happens if R1 is incorrectly chosen? Could too much current through D1 push back on D2 and prevent flow ...
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3answers
167 views

Is the “antenna aperture” the same as the “hole in the shield”?

Is the concept of the "Antenna Aperture" the same as a hole in a electromagnetic shield? The wikipedia article is quite vague, and I am a newbie in this field. For example if we have an electric ...
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2answers
147 views

Basic Capacitor Question To help Cement My Foundation Properly (LTSpice)

I have the following circuit in LTSPice. I can see +- 3.5 uA of current at various nodes. I should be able to calculate the 3.5 uA given the R and the C. I note that the sim output is sinusoidal. ...
2
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2answers
380 views

Ultra-basic question: where is the voltage in this simple circuit diagram?

I'm trying to understand the role of pull-up resistors, and keep coming across this basic circuit diagram illustrating the "floating" condition. I'm struggling to understand how the switch at S1 ...
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1answer
964 views

Input voltage/current required for LM1117 3.3 Power Regulator

Can I use Mobile charger having Output Rating of Voltage 6.0V / Current 300mA as input to LM1117 3.3 Chip. If possible - Will it be able to provide 800mA current when required and how?
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3answers
114 views

New to EE classes, have an introductory voltage output problem

sorry if this seems very easy but I am looking for a little help as I have only just begun to learn EE. My homework problem has me create a power supply using a common reference point only a 24 V ...
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1answer
1k views

RMS of a complex waveform

For a complex waveform as follows: One can find the squared rms of the complete waveform by finding rms of individual components and then square multiplying it with the corresponding duty cycle. $$...
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2answers
302 views

Voltage between points of different batteries

Let's say I have three points: A, B and C. I measure the voltage between A and B: it's 0. I then measure the voltage between A and C, and it's again 0. So, the voltage between B and C must also be 0, ...
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2answers
176 views

How correct is my understanding of basic electricity?

I have a very basic way of understanding things. Sometimes I over-complicate and sometimes i make it way too simple so I am hoping someone can help me judge my understanding of basic electricity. I am ...
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2answers
97 views

Basic circuit with diodes analysis

I have the following circuit: How to determine the waveform of Vout, maximum values for positive and negative half-period segments, and the average value of Vout? Input voltage Vin has a sinusoidal ...
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1answer
53 views

Is electric charge a state variable since derivative of charge flow is defined as current?

\$ i=\frac{dq}{dt} \$ Is 'q' a state variable in general?
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1answer
46 views

Electro-static potential of a capacitor during a transient?

How would I calculate the electro-static potential for this simple circuit during the transient (during the time the capacitor charges)? Do I just use Ohm's law? simulate this circuit – ...
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3answers
357 views

Basic Capacitor Discharge [closed]

I found this illustration from the SparkFun website on how a capacitor charges and discharges, but I have some difficulties with it (and capacitors in general): What initially causes the capacitor to ...
0
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2answers
112 views

While discussing eigen functions of LTI system, why we ignore the natural frequency term in response?

Consider the LTI system, a series RL circuit (initially at rest). If we define voltage as input and current as output, whatever be the forcing function, output contains a component \$ e^{-Rt/{L}}\$ ...
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1answer
3k views

MOSFET bulk connection to the source

Why is bulk always known to be associated with source and not the drain? What would be the result or outcome if I connect the bulk to the drain instead of the source?
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3answers
2k views

What happens if you add a voltage source to the output of an op-amp?

I'm trying to self-learn EE and have a question: What happens if you add an external voltage source to the output of an op-amp? Say as in this picture: I know that WITHOUT the Va, Vout would just ...
7
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1answer
532 views

Vacuum diode in space charge mode: emission current

This must be a rater basic question about terminology. I frequently come across the following statement: when vacuum diode is working in space charge mode (as opposed to saturation mode), the cathode ...
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3answers
218 views

3.3V/5V Linear Regulator Voltage to Ground Jumper

I received this 3.3V or 5V power supply. It's neat because it fits on my breadboard and can provide two separate voltages (chosen using jumpers) on it's two outputs. I originally thought that this ...
3
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2answers
769 views

Circuit analysis on op-amp with no negative feedback

In this diagram, there's an op-amp with no negative feedback. What is V+ (voltage at positive end of op-amp)? I'm self-learning circuits, and a resource I'm using says V+ = V3 / 2R. However, I don't ...
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4answers
1k views

In solving an op amp problem with two voltage sources, why can't we combine it?

Say we have a circuit like Why can't we solve by doing $$V_{out} = -(V_{in} - V_{offset}) * (R_f / R)$$ We know that \$V_{out}\$ for a typical inverting amp (that doesn't have \$V_{offset}\$) is ...
2
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3answers
196 views

Help me solve this TAOE problem

So, I picked up this book and am working through it by myself. I am a bit stuck on problem 1.6: In the bottom you can see how I'm approaching this. I'm assuming the transmission cable goes across NY, ...
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1answer
1k views

Is a load needed to measure the voltage drop of a long cable?

Should be a simple yes or no question. If I attach 20ft of 16AWG cable to a power supply, in theory I should see some voltage drop. Do I need to place a load at the end of the cable to read the ...
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2answers
1k views

why electricity requires a closed loop to flow?

Imagine a battery with the positive terminal connected to ground. The positive side has a high eletrical potential, ground obviously has a lower electric potential. Electricity wants to seek a lower ...
1
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2answers
398 views

Understanding an N-JFET

I am currently learning about FET transistors, and there is some things that I do not understand about an n-type JFET. I have two question about this transistor. Why is Vgs important and how do we ...
1
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1answer
159 views

In a real-world op-amp, how does it make sure Vn and Vp differs and don't equal each other?

I was confused about op-amps and asked this question: In an op-amp, why does Vn approach Vp until the difference is delta V / A? Why doesn't Vn just equal Vp? and received really helpful answers. ...
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2answers
1k views

In an op-amp, why does Vn approach Vp until the difference is delta V / A? Why doesn't Vn just equal Vp?

In an op-amp (non-inverting), when \$V_s\$ increases by \$\Delta V\$, \$V_n\$ approaches \$V_p\$ until the difference is \$\Delta V/ A\$ (where A is infinity). Why is there the \$\Delta V/ A\$ ...
0
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1answer
94 views

Measure currents (~50 mA) at every 10 microseconds interval and store the data [closed]

I'd like to measure the current across a tiny load (current range is maximum 50 mA) at every 10 microseconds, and store these values for later reference to plot a Current vs Time graph. Is it possible ...
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2answers
1k views

Audio amplifier schematic explanation

I'm repairing an old amplifier Sansui A-40 which I got from a friend. Here's a portion of the original schematic: What does the red marked area do, and how does it work? I'm not familiar with that ...
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1answer
826 views

Relationship between voltage/current & LED strips?

I recently bought a WS2812 LED strip (5 meters, 300 LEDs) When the LEDs are driven at full brightness and each color lit, they draw 60mA each--or 18 amps for all 300! This led to a problem, which ...
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4answers
80 views

Help me understand dielectrics

So, they're insulators or poor/non-conductors of electricity. Yet somehow they are also capable of holding and/or transmitting an electrical charge. Does that not seem like a crazy paradox, ...
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3answers
1k views

Good analogy for watts vs amps?

According to plumbing analogy I've hard time seeing why power is measured in volts*amps, instead of just amps. I found an analogy from http://science.howstuffworks.com/environmental/energy/...
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1answer
933 views

High power IR transmitter circuit for ESP8266

Currently I am using this IR transmitter circuit for an ESP8266: It works, the reception is not bad, but I need a little bit higher power to control my AC unit. The AC unit is ca. 10 meter away from ...
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1answer
92 views

when a capacitors is being charging from a battery is battery discharging?

I'm studying yet. Is a battery discharging when capacitor connected to it is charging? Please explain how does it work!
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3answers
447 views

Calculating the dropper / series resistor for an LED [duplicate]

I'm so sorry if this is a stupid question. I have read some of the questions previously asked but in afraid the maths and physics are way over my head. I have made a wooden template and would like it ...
0
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1answer
95 views

Is it possible to control distance of RF Transmitter

Noob question here, is it possible to control the distance range of RF transmitter. I need a RF transmitter application where i can control its distance with pot.
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2answers
438 views

Understanding voltage and current - is there voltage without current flow?

I'm trying to increase my knowledge of electric circuits and their major components. My current understanding is very basic, which will explain why my question may seem laughable to most people on ...
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2answers
419 views

adapting 60 LED battery operated string-light to work with wall wart

I need to adapt one of these 60 LED string-lights to be powered through a wall plug. These are micro LEDs all wired in parallel; sadly, I couldn't find specs for this kind of LED. The string's power ...
0
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1answer
405 views

Current flow with a Diode [duplicate]

I'm just starting out learning about Electronics but something has puzzled me . I have read that current flows through a circuit from negative part of a battery to positive . but what puzzles me is ...
0
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1answer
112 views

What is this torus wire coil next to dc motor?

I'm currently playing with a cheap $7 RC car from the toy store, and has just started out with arduino and electronics. What is the purpose of the torus thingy with wire going around it, between the ...
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3answers
150 views

What is the correct way to read color codes? [duplicate]

For example, The resistor above has four colors. Green, blue, red, gold. My calculation says its value is 562 ohms +-10%. But this page says its value is 5.6K-1/4W. What is my mistake?
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4answers
2k views

Why is an infinitely large capacitor a DC open circuit?

This really sounds like a stupid question, but I believe it's worth asking: Due to \$I=C\frac{dU}{dt}\$, and \$C\$ is infinitely large, any minor change in \$U\$ would result in infinite current,...
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1answer
191 views

Why resonant charging produce “no current immediately after discharge”?

It's me again, still reading AoE 3rd. On page 40, footnote 35, the author writes: Resonant charging is used for the high-voltage supply in flashlamps and stroboscopes, with the advantages of (a) ....
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2answers
2k views

“A zener with series diode”?

So I'm still reading The Art of Electronics Third Edition. On P.39, when dealing with indicative "kick", I found this sentence: For the fastest decay with a given maximum voltage, a zener with ...
1
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1answer
697 views

What does an “ac coupled signal” mean?

I've heard this term many times from many different sources, but none of them gave me a definition. Here is my understanding: "coupled" means "connected together". If two circuits are "capacitively ...
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1answer
501 views

Large capacitors “producing more I²R heating”?

On page 35 of The art of Electronics Third Edition, when describing the disadvantages of reducing ripple by choosing large capacitors, the author writes: The very short interval of current flow ...
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0answers
151 views

The Art of Electronics exercise 1.19 [duplicate]

I'm reading The Art of Electronics(3rd), and I'm just stuck with exercise 1.19. Here is the question: Explain why L∝n² for an inductor consisting of a coil of n turns of wire, maintaining fixed ...
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2answers
130 views

Unable to make a pot work correctly

I have a board I salvaged from a joystick that uses potentiometers to measure the location of the arms. On the PCB a edge pin and the center pin are wired together. I would like to connect the pots to ...
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2answers
785 views

Simple transistor motor driver does not work properly?

The transistor gets hot to the touch and the motor will continue to run when I disconnect the transistors base from 9v+ (I am trying to make sure the circuit works before I hook it up to an arduino). ...
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5answers
11k views

Why is capacitor a linear element?

Why is a capacitor a linear device? One property for linearity is that the capacitance or some such parameter must not change with voltage or current. Is this enough to make a device linear? A few ...