Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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45 views

Why is my voltmeter output incorrect

So I'm completely new to electrical design. I thought I'd try out the most basic experiment I could think of. Here I hooked up two AA batteries to a breadboard along with a 10 K resistor. When I ...
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2answers
88 views

Will Kirchoff's voltage law work in a vacuum

Kirchoff's voltage rule tells us that the sum of voltages around a closed loop in a circuit will equal zero. If a battery sits on a table, using KVL and treating air as matter with high resistance ...
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1answer
31 views

resistor combination circuit

simulate this circuit – Schematic created using CircuitLab This is probably a very stupid question. I am new to electrical engineering in general, I was working with NOT transistor gates in ...
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1answer
26 views

Multisim Multimeter showing blank reading (--------)

I am trying to build a simple circuit to back up some hand calculations that I am completing for a project. However I am unable to get a reading on the Multisim multimeter. I have changed the ...
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3answers
107 views

Why does the impedance of a parallel RLC circuit approach infinity at resonance?

Pretty new to this stuff so apologies if I get some words wrong. In the book I'm reading they described a parallel circuit with a resistor capacitor and an inductor powered by a current source. They ...
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2answers
100 views

Why does pin numbering and placement (in general) appears to be done so haphazardly to the uninformed person (me)?

Be it an ESP development board, an IC controller, even an LED segment number itself, pin placement never seems to follow a logic when it comes to actual numbering, or function. I can't find a simple ...
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1answer
132 views

Filter w/ seemingly higher output voltage than input?

I'm working on a simple LC filter as part of an AM radio project. I was intending to use a ferrite antenna (modeled roughly by the voltage source in series w/ inductor which is then connected to a ...
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4answers
294 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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4answers
145 views

What is the relationship between electrical resistance and heat generation? [duplicate]

An incandescent light bulb has some amount of resistance (let's say 30 ohms) and generates a large amount of heat. It's my understanding that a resistor with the same amount of resistance (30 ohms) ...
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1answer
57 views

I want to understand this audio input to LED output simple circuit

I'm a newbie in electronics. I watched a youtube video that showed how to activate LEDs using a microphone. It's project #3 at https://youtu.be/zsJ61yJhWVU?t=115 The guy built the circuit on camera ...
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1answer
113 views

How do I ground my power supply?

I have a Meanwell GST120A24-P1M +24V power supply (picture below). I want it to power a circuit of mine. Say the circuit is as shown below: one power supply and one resistor. How do I connect the ...
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0answers
42 views

Noob Question, 74HC240 and Solar Cells

My idea is to start soldering and I would start with something quite simple. I chose the project (https://cdn.makezine.com/make/08/pummer.pdf), a pummer with solar cell charging up a supercapacitor ...
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4answers
878 views

How do I determine whether a switch can handle the power/current in a circuit?

I have a switch that has "3A 250VAC" and "5A 125VAC" printed on it, which I imagine are ratings of what the switch can handle, but my understanding that 3A at 250V would be 750W ...
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2answers
46 views

Basic Series/Parallel connection understanding

I am just starting out with electronics and I have understood that there is something fundemental I just cant seem to figure out about parallel and series connections. I am having a lot of trouble ...
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1answer
92 views

Is it safe to cut these wires?

My kid got a face mask with flashing eyes, but there's also some annoying sounds that comes with it. Is it totally safe to cut the white wires or could the awesome flashing lights stop working too (...
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1answer
111 views

Circuit with 1 diode in parallel with a resistor

Sorry if this question has been answered here before, but I just can't seem to find any info on this. A little background. I am currently doing an automotive mechatronics course and, while I know some ...
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5answers
220 views

Basic BJT current mirror : … so the collector-base voltage of Q2 is also zero?

From this schema I don't understand this sentence from here, particulary in section "Basic BJT current mirror" "...If Q1 and Q2 are matched, that is, have substantially the same device ...
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2answers
69 views

Please help me with finding if I need to add a resistor to my circuit

I want to connect 3 4V LED strips in series to a 12V, 1A supply. Each strip requires 250mA current to operate. This makes a total of 750mA required current for all 3 strips. My concern is how should I ...
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1answer
59 views

Resistor across output?

I'm trying to learn about gates.Why is a resistor connected parallel across the output?
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2answers
80 views

RC Low Pass filter, capacitor in series or in parallel?

I've seen 2 variations of the RC low pass filter, sometimes with both the resistor and capacitor in series, and more commonly with the capacitor going straight to ground. What is the difference ...
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2answers
164 views

Reverse biased diode

What would be the voltmeter reading in the following circuit?
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3answers
221 views

Why does the voltage drop across an LED matter when determining an appropriate resistor value?

In determining the voltage dropping resistor, why is the forward voltage of an LED deducted from the supply voltage instead of considering the supply voltage alone?
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1answer
500 views

Wiring RGB Strip LEDs w/ just positive and negative wire [closed]

I'm working on a small project, and I had some leftover strip LEDs lying around. They're just the RGB strip LEDs you can pick up at Five Below. They come with an RGB controller attached to a short USB ...
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1answer
61 views

steady state voltage in capacitor network

simulate this circuit – Schematic created using CircuitLab I have this capacitance network in my circuit and I can't figure out the math behind why the final steady-state value of Vx=0.542v when ...
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2answers
47 views

Resonant frequency and maximum signal width

I've seen resonant frequency being defined as the point where the input signal is in phase with the output signal (So reactance/susceptance is 0). However conceptually, teaching material seems to link ...
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0answers
87 views

Audio amplifier circuit explanation

Recently, I am working with amplifier circuits but circuits available online for an op-amp have some extra components with respect to what we learn in textbooks. I know the basic amplifier components ...
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1answer
58 views

Current Divider with dependent source

I'm currently studying electronics for the first time. The objetive of this exercise is to calculate the current I and the dissipated power in the dependent source. However, I'm having a hard time ...
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1answer
34 views

Trigger two circuits with single SPST switch

I'm an electronics noob willing to learn. So I have a door bell that looks like it is wired like this: And I've bought a fancy 3V battery powered device that is intended to be wired simply like this:...
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2answers
80 views

Output characteristics of transistor

Why is the slope of output characteristics of transistor in CE configuration more than that of CB configuration??
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1answer
177 views

Find the Thevenin's equivalent of a circuit between nodes A and B

My class had come to discuss the Thevenin's theorem and we stumbled upon this particular problem which quite confuses me in a way that what I found is different than what my lecturer taught us. So, ...
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1answer
100 views

Power supply module on breadboard giving too much voltage

I'm currently following the tutorial "Electronics Fun Kit" by ELEGOO. The goal is to connect the power supply module with the breadboard in order to provide a 3.3V / 5 V source. After connecting the ...
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1answer
43 views

(Basic) How to connect the ground in this schematic to a breadboard?

I just want to know how do I connect the ground in the circuit. I know how to connect DC source but I'm confused on how to connect the ground. I have adept knowledge about the concept of ground, I ...
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0answers
67 views

Testing a LM111P comparator

I have the LM111P voltage comparator (datasheet.) I am learning my ropes with electronics, so I am moving thru the easiest topics to more complicated ones. If I understand correctly, when I provide ...
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0answers
53 views

Separation of channels in simple audio LED VU meter

I'm trying to build a very simple VU meter based on LEDs and transistors. I used this tutorial as a base - basically I copied the LED array setup but replaced the input with full bridge rectifier. My ...
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5answers
2k views

Why is it called Wired-OR when it is functioning as Wired-NOR?

Inputs: Base of bjts Output: black node When at least one of the inputs is HIGH the output is LOW. This is clearly NOR. Then why everyone calls it Wired-OR?
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2answers
100 views

Op amp outside resistive network

Usually I don't care about algebra and just focus on the functionality. However, below circuit form appeared so many times in last few days in op amps that I thought of memorizing it by heart. From ...
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3answers
151 views

Two charged capacitors connected in series

simulate this circuit – Schematic created using CircuitLab The circuit has the initial condition as shown in figure. What will Vfinal be when SW3 and SW2 are open but SW1 is closed.
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2answers
59 views

How is it possible to force \$v(t)=\cos(t)\$ as voltage input to a fully discharged capacitor?

Let initial charge on capacitor \$Q=0\$ and say \$v(t)=\cos(t)\$ is applied for one period(\$2\pi\$ seconds) across the capacitor. Then the current will be \$i(t) = C\cos(t+\pi/2)\$. Clearly the ...
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3answers
79 views

In an equation like i(t) = CdV/dt, is “V” the cause and “i” the effect?

In mechanics, almost all the time, force is the cause and acceleration the effect. If you apply a net force on an object, an acceleration can be observed. However this seems not that straightforward ...
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2answers
43 views

How does difference in loads affect current draw

This is a side question to 487370/limit-charging-current-to-a-smartphone. Hopefully it will clear the confusion in my head. Say we start at 5.5V with a series resistor of 1 ohm, that will leave 5V ...
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2answers
84 views

Transformers and wattmeters

This is, probably, a very silly question, but I was thinking: If you have a watt meter and you connect a step up transformer with the lower voltage side attached attached to it (both the voltage and ...
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2answers
67 views

Thevenin's voltage

I'm trying to solve and exercise (see picture) where I'm supposed to find the voltage drop between 2 points in a circuit, using Thevenin theorem. I removed the resistance between those two points. ...
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4answers
76 views

How do I find the missing equation?

This is my first post here, hope you all doing well. I'm a CS student, having my first class on circuits. I've been given this problem (see picture) where I'm asked to find V2. I'm missing one ...
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3answers
140 views

How Does Kirchoff's Law Make Sense

I understand the algebra, and I can also use Kirchoff's Law in calculation. But I struggle to understand how it makes sense logically. The law states, that the sum of the currents entering a ...
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3answers
120 views

Why are LEDs so tolerant of voltage?

My electricity knowledge is about high-school level or so. Just about enough to be dangerous... Back when I was a kid I used to play around with 4.5V DC power sources, buttons, switches, relays and ...
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5answers
174 views

Will a capacitor draw charge/current if it's not feeding a load?

I have a number of capacitors connected in parallel, as in the following circuit: simulate this circuit – Schematic created using CircuitLab If the switch is open, will the caps still draw ...
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0answers
67 views

8000 Amps across a 1 A diode for 0.2 uS

Assuming that the diode is rated for 20 kV and the pulse is only 250 V, will a 250 V 8 kA pulse that lasts 0.2 uS break a 20 kV 1 A diode? This also assumes that the diode recieves 10 of these pulses ...
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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 ...
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1answer
37 views

How to calculate voltage of these nodes

How exactly does one calculate the voltage of the marked nodes and arrive at the numbers in the picture (1.75 and 1.628)? I fail when trying. :( simulate this circuit – Schematic created using ...
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1answer
33 views

Comparing transformer set ups

Is it practical to connect the output of a ferrite-core 1:40 transformer in series with the input of a 1:6 ferrite-core transformer as a means of acquiring 240 V?What would the pitfalls be of this ...

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