Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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64
votes
8answers
7k views

Can a circuit be powered from Earth with a return ground on Mars?

Could you use a hot wire (120v 60 hz) from earth and a copper rod inserted into another extraterrestial body (mars) to complete a circuit? If impedance wasn't something to worry about (pretend Mars is ...
38
votes
10answers
6k views

What is a Charge?

I'm a high school student. I love computers and electronics. Few weeks ago, I thought to build my own electronic gadget but, unfortunately I had not much knowledge in electronics. So, I decided to ...
25
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9answers
35k views

LED and lamp in series - why does the bulb not light?

My 6 year old son has just started experimenting with a Snap Circuits style kit and already we have a very basic question. If we arrange an LED and lamp in parallel powered by batteries then both LED ...
25
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6answers
34k views

ATMega8: why do VCC and AVCC have to be connected?

I often read that it is good practice to connect VCC with AVCC. Even in the ATMega8 datasheet it says so: AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..6). It ...
22
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9answers
4k views

Why are electrons not pushed out from the conductor at an open circuit under the influence of a power source?

Frequently, electric current is compared with water flow. For example, if I make a hole in a water tank, water will flow till the tank pressure and the atmospheric not become equal or the tank becomes ...
20
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13answers
5k views

Path for a child to learn electrical engineering

What are some paths for a child (7-year-old) to learn electrical engineering (in a safe way)? I do not want to saturate (or frighten away) the child with lots of concepts, I want that my son learn ...
19
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6answers
2k views

Do electrical devices “take what they need”

One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them. If a motor needs 12 volts and ...
17
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3answers
4k views

What operation could cause the inductor or the capacitor to explode?

In really early days of electronic school, the teacher used to say something about not unplug power too quickly at an inductor or capacitor and we were used to slowly turn the voltage generator from a ...
17
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2answers
32k views

How does an astable multivibrator LED blinking circuit work?

I am a beginner in electronics. I come to know about the oscillator using RC circuits (capacitor charge and discharge and time constant tells the behavior of circuit). Then I saw the following ...
16
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5answers
36k views

How do I connect two identical batteries to increase the consumer lifetime?

If I've got a device that uses a single battery, and with that single battery, the device lasts an hour, and I want the device to last for two hours, I'm assuming I can wire two batteries up and it ...
15
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3answers
6k views

Basic operation of a bipolar junction transistor

I've tried really hard to understand the basic operational principle of a transistor. I've referred to many books and been to forums but have never got a convincing answer. Here are the things I want ...
14
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6answers
4k views

How does an SR Latch get started [duplicate]

Noob question, but I'm not seeing how an SR latch such as the one in the image can "get started". If each input depends on the output from the other, how can there be two inputs to each gate to set ...
13
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5answers
57k views

Why should a circuit be grounded?

Why should a transistor circuit be grounded? The way I understand it is that ground is an infinite supply of electrons and so it is equivalent to the negative terminal of a battery. But in this page , ...
12
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6answers
3k views

Why are crystal oscillators used in clocks instead of RLC circuits?

The timing of quartz clocks is regulated by a crystal oscillator. This crystal oscillator effectively forms an RLC circuit. If this is so, what properties does a crystal oscillator have that makes ...
12
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4answers
34k views

How can I learn electronics at home? [duplicate]

Possible Duplicate: Learning about electronics I am 40. I am an architect by profession. I am very interested in learning electronics. I don't have time to go to college for an electronics ...
11
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4answers
14k views

555 timer: how to set values to take an hour

I'm new (and novice) in electronics. I came to seek your knowledge to see if someone can help me with a very basic circuit. It is a 555 chip, which should light a LED (for about 1/2 second) every ...
11
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4answers
3k views

Rocket launcher circuit design

I'm building a model rocket launcher with my son. The circuit is very simple as you can see. We want to add a buzzer and a LED/bulb when it is turned on as a warning to stay clear of the rocket. How ...
11
votes
7answers
3k views

From zero to “almost pro”: Newbie trying to learn. Good, quick resources?

I am a total zero in electronics. I just know what is a resistor and what is a capacitor. I also know what is a 555 just because I've been told what it does, 15 years ago. Apart from this and a bunch ...
11
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2answers
1k views

What role does this diode play?

I've just bought an Arduino Uno kit, and am going through all the projects in the booklet that comes with the kit. From even the simplest LED and resistor circuit, to get a feel for the Arduino board, ...
11
votes
2answers
82k views

When to use a 1/4 Watt resistor vs 1/2 Watt resistor

I have never understood the difference between 1/4 & 1/2 watt resistors, and in all of my EE lab courses I have always just used 1/4 Watt resistors. When does one use 1/2 Watt resistors and what ...
11
votes
2answers
42k views

Connecting a potentiometer

I know how to connect potentiometer, but to be honest I don't know why. I would really like to understand what I'm doing. From what I have read the input voltage and the ground should be connected ...
10
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9answers
39k views

How can voltage burn out an LED?

I understand how a current higher than what the LED is rated for can burn out an LED, but how does something equivalent happen with voltage? If the correct current is on an LED but the voltage is too ...
10
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5answers
16k 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 ...
10
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3answers
9k views

Is capacitor reactance [sometimes] defined with negative sign?

Wikipedia currently claims so but I've looked in 6 books via Google Books and it's not defined like that, i.e. it's just $$ X_c = \frac{1}{\omega C} = \frac{1}{2\pi f C} $$ Is Wikipedia full of ...
9
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4answers
4k views

Do capacitors waste power as heat or whatever on AC?

Capacitors store energy then give it back once required. A perfect capacitor is nearly lossless on DC power because you only fill it once then it keeps energy in it until you discharge it so no power ...
9
votes
5answers
41k views

High Current or High Voltage that damages components?

Very basic question here and I'm only looking for a generic over view, but is it a too high current or a too high voltage that will damage electronics? I assume it will depend on the component in ...
8
votes
6answers
7k views

What is an amp (and other such basic questions) in the simplest possible terms?

I understand that this is a really basic question, but, I've been unable to really understand electrical terminology for some reason. What exactly is an amp? How does it correspond to a watt? And: ...
8
votes
8answers
3k views

What are analog and digital signals?

I came across the concept of analog and digital signals in my data communication course. We studied that analog signals are continuous signals and teacher presented a diagram like the sine wave and ...
8
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8answers
15k views

When does the placement of a resistor matter?

I've been a programmer for years but am very new to electronic engineering. So far I see people saying it doesn't matter where a resistor goes in your LED circuit as long as it is present, but it ...
8
votes
6answers
39k views

How electrons inside copper wire behave when source is ac or dc?

When a simple copper wire is connected to AC or DC, what actually happens to the electrons inside the wire? I.e. What kind of path do they follow when they reach the end of the wire? If anyone can ...
8
votes
1answer
1k views

How do you interpret/draw out the simplified circuits in Sedra's Microelectronics?

I legitimately do not understand how the simplified drawings in this book are meant to be interpreted. Coming from a basic circuit analysis class which had everything explicitly drawn, I'm having a ...
8
votes
2answers
8k views

Designing a cable tester

I need to check the integrity of 40+ custom cables. Each cable is meant to be the same, and is meant to have 19 ways. I bought an enclosure, some mating connectors, some LEDS and a bunch of ...
8
votes
1answer
729 views

Understanding this circuit with op. amps

I'm studying electrical engineering and I've came to a problem, where I cannot proceed. It's a "simple" task, where we're talking about an inverting op.amp with 2 voltage sources, each 1V, while all ...
8
votes
2answers
38k views

Why 10Log(p1/p2) and 20Log(v1/v2)? Why not just 10Log(x1/x2)? [duplicate]

Based on my very basic current understanding of decibels in electronics, it is said that I should use the db = 10Log(p1/p2) formula if I want to calculate the power ...
8
votes
3answers
4k views

Transistor Toggle Not Working

I'm trying to learn about how transistors work. As a simple test I created the following circuit: My idea is that when the second transistor will keep the first one active after I click the button ...
7
votes
6answers
2k views

Decrease in stored energy after connection of another capacitor

A 3-µF capacitor charged to 100V is connected across an uncharged 6-µF capacitor. So the initial stored energy is: 15mJ and the final: 5mJ. What happen to the 10-mJ of energy?
7
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4answers
4k views

Transistor with two voltage levels, Vb ≠ Vcc

Why is my transistor only driving 5V instead of 6V? How can I fix it? I have a 6V, 25mA circuit running some LEDs. I can control them by connecting and disconnecting the positive terminal of the ...
7
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5answers
8k views

Why pulsed DC passes through a capacitor?

OK, the current flowing through a capacitor equals C*dV/dt, I'm aware of that. What I don't understand is the physics of the process: why does a capacitor pass pulsed DC (0-10V for example) when ...
7
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3answers
48k views

How does current flow through a voltage source?

Im going back to electricity 101 to understand several things Im missing. One of them is exactly how does current flow through a DC source. Heres my understanding: A voltage source is one which has ...
7
votes
1answer
4k views

Basic rules to calculate the equivalent resistance of a resistor circuit

I have a certain circuit only containing resistors of different values. There is one 'input' and one 'output' for the current. How do I calculate the equivalent resistance of the circuit? Are there ...
7
votes
5answers
4k views

Learning about electronics

I'm a computer scientist with zero exposure to things directly related to hardware (barring what I learned from my undergrad computer org class.) I've been very attracted to the field of embedded ...
7
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4answers
22k views

Why would we need to ground an AC source?

I'm new to this field hence this weird question. Why would we need to ground an AC source? Why wouldn't it be enough to have just one pole to get an AC current going? I understand why it wouldn't work ...
7
votes
4answers
3k views

Where can I find beginners electronics project schematics online, for free? [closed]

I have bought the following books in order to start learning basic electronics: Electronics All-In-One Desk Reference For Dummies Robot Building for Beginners (Technology in Action) My desire though,...
7
votes
3answers
25k views

How to amplify electret microphone to range from 0-5V with bias of 2.5V?

I'm new to op amps and have tried many circuits but don't get the results I expect. I know I must do some math but I get so confused. I thought my question is really simple but it turns out it's not. ...
7
votes
2answers
9k views

How to wire a GSM module to my alarm system

I have an alarm system that has been installed by an alarm dude ;) I want to add a GSM module to the alarm system, so that I'm notified when the alarm is triggered. Before I purchase the module I ...
7
votes
1answer
768 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 ...
6
votes
8answers
14k views

What is negative current?

I understand that voltage is relative to ground, so that can be negative. However, I'm currently looking at current-sensors (ACS712 current sensor) and in the performance characteristics table, it ...
6
votes
5answers
5k views

How can a circuit not have a neutral?

I've been making plans to install a NEMA 6-50 outlet in my garage, but I don't understand how it can not have a neutral, and instead have two hots (at 120v each) and a ground. What completes the ...
6
votes
1answer
10k views

What does lumped element mean?

Can anyone explain me the meaning of lumped element and lumped circuit abstraction in detail. What does lumping or discretizing matter mean?
6
votes
4answers
340 views

Simple power on delay for 3.4v-5v serial device being powered by 5volt VCC

What I am trying to do I am trying to build the most simple as possible circuit to give a 3.4v-5v serial device a 1-2 second power on delay from the embedded Linux device running at 5v that it is ...

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