# Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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112 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 ...
51 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:...
108 views

### How to get started with learning electronics? [duplicate]

My main goal is to be skilled enough to design printed circuit boards to build devices like a basic smart watch and other simple projects. How do I get started ?
230 views

### Output characteristics of transistor

Why is the slope of output characteristics of transistor in CE configuration more than that of CB configuration??
410 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, ...
200 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 ...
46 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 ...
120 views

### Calculating Vo in the following problem

I'm sorry I'm totally new to electronics and I get confused of what Vo is in such problems and how to calculate it so can someone explain what Vo is and how to calculate it
68 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 ...
77 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 ...
853 views

### Roadmap for learning Electrical Engineering [closed]

I am just starting to learn electrical engineering, but I am confused about what I should do. Should I be reading about it, taking online classes, or just make projects? If possible can you provide me ...
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?
107 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 ...
308 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.
60 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 ...
100 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 ...
47 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 ...
125 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 ...
73 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. ...
79 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 ...
148 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 ...
147 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 ...
291 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 ...
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 ...
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 ...
40 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 ...
35 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 ...
78 views

### How to prevent common ground circuits messing with each other

I made an Arduino based 18650 battery tester that has 4 identical circuits that charge and drain. Testing one battery at a time gives one set of results which I deem to be correct but testing more ...
483 views

### Wiring a Potentiometer for a positive voltage

I am attempting to make my own adjustable voltage supply that provides a positive voltage (anywhere from 0 to +200 VDC). The sections I have devised so far are able to provide 450 VDC, however I need ...
103 views

### Alternating voltages on vintage calculator circuit board

I am an electronics novice. I have a vintage calculator with six secondary wires coming out of its transformer and ending on the board, as shown below: Using the AC portion of the multimeter, I ...
219 views

### 220 volt step-down transformer with 6 secondary wires

I am an electronics novice. :) I opened a working Casio vintage desk calculator (likely from the late 1980s/early 1990s). It has a 220 volt step-down transformer with six secondary wires. The two ...
56 views

### Preservation of power when wiring batteries in series - battery life is reduced if load is kept the same

This is really just a "sanity check" type question. Am I correct that if you place two batteries in series, that the battery life is effectively halved relative to just one battery, assuming the load ...
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 ...
112 views

### Help explain op-amp description by Forrest Mims

The following description is from the book Op-Amp IC Circuits by Forrest Mims (2nd edition 1994): As a newbie, the entire paragraph is counter-intuitive to me. If amplitude is reduced, why is there ...
48 views

### Voltage Rating of Capacitor Set Up

A buddy of mine just told me that the set up (linked to the question on Circuit Lab) would be able to handle 500 volts DC, even though each capacitor is rated for 20 volts DC. It was to my ...
120 views

### PIR sensor bypass for LED light strip

I don't know that much about electronics, but I was able to put together this PIR module: (original) and a LED strip and everything works just fine, when the PIR detects motion, it turns the strip ...
888 views

### Electricity path through a 240V heating element

My simple understanding of electricity is that you always need a circuit (from + to -, or from hot to neutral), in order for current to flow. Now, I recently had to fix my water heater (which is ...
83 views

### How can I make a simple circuit to output only after a min input voltage is exceeded?

Here's my problem.... I am setting up a camera system on a motor coach that is designed to trigger separate cameras when blinkers or backup is engaged. the problem I'm having is the only accessible ...
101 views

### Explanation results of RC simulation wih LTspice/Micro-cap

I built a basic schema with resistor, capacitor, ground and a battery in LTspice and MicroCap. I used transient analysis mode. I expected to see on a chart decreasing current and increasing voltage ...
220 views

### Replacing a 1.5V with a 5V power source

I've got a motor that's driven by a 1.5V battery. The shaft turns slowly and that's the way I'd like after replacing with a USB cable (5V) source. In the current circuit there's no resisters (just a ...
2k views

### How is a series resistor limiting the voltage for a diode?

I try to understand some basic concepts, but I'm stuck with this question. I have this schematic, with a power supply 9V, a resistor 450ohm and a LED. Assuming the LED consum 16mA, this resistor have ...
226 views

### Why the power supplies limit the amperage?

I'm just learning electronics, and I can't understand something: If the amperes don't matter in terms of burning the circuit, only voltage, why do phone charges for example have a low current ...
191 views

### Ringing seen when a zener diode is used with series diode as a snubber

I am trying to simulate the snubber circuit as given in "A zener with series diode"? there is some ringing seen at ouput. Here is LT spice ckt: Simulation result shows some ringing at ...
363 views

### IR Detector with two indicating leds

I have basic undestanding of electronics, but I never build anything more then simple one element logic boards. I know how transistor, resistors, and LEDs works, but I having trouble figuring out ...
57 views

### Capacitive Power Supply Torch

I'm an amateur at electronics circuitry and concepts. I have designed a simple capacitive power supply using few web images and brief lessons. I understand that this type of transformerless power ...
69 views

### how is this transformer working with DC? [duplicate]

As I was going through the SMPS circuits online I came across this circuit: I searched and learned that the transformer steps down or step up only AC power supplies and then converted to DC using ...
80 views

### Analogy to explain why an antenna must be (in order) size of wavelength

An antenna has to be sized on the order of the wavelength because we want waves to form. Waves mean, very roughly speaking, different "state" (current, voltage, water level, ...) at different ...
192 views

### Multiplication of average voltage and current?

Multiplication of $V_{rms}$ and $I_{rms}$ gives average power. What things we get if we multiply $V_{avg}$ and $I_{avg}$??