# Tagged Questions

Fundamentals of electricity, electronics, components, or theory

60 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?
531 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 ...
29 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) ...
310 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 ...
48 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 ...
440 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 ...
70 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 ...
51 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 ...
57 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). ...
2k 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 ...
115 views

### Is there any generalized symbol for an electrolytic or electroplating cell?

Is there any symbol for an electrolytic cell? An electroplating cell, for instance? (There are commonly used symbol for electrochemical cell (battery symbol). But symbol for electrolytic cell not ...
168 views

### How does a 700W PSU deliver so much power when most wall sockets are limited to about 20 amps?

I will be using a computer power supply to power a car audio amp for a project. The amp is 500w and my PSU is 750w. I never considered it until now, but how does the PSU deliver this? P=VI so 750w=...
126 views

### Where do these grounding wires go? [duplicate]

In the following schematic the two Vss pins where are supposed to be the grounding pins don't connect to anything. Does this mean that the circuit is self-grounding (if that's even a thing)? I'm ...
1k 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 ...
107 views

### How to calculate the output impedance of this circuit?

This is a hybrid-pi model of a BJT, and I want to know its output impedance: simulate this circuit – Schematic created using CircuitLab I know that I should short the input ports, place ...
46 views

### Conditions for Thevenin and Norton non-existance

It's not clear to me when a Thevenin or Norton equivalent cannot be produced for a given linear circuit. Can anyone help me with a clear definition? Thanks!!
56 views

### Why Can't I get a Smooth Sine Curve in PSPICE

I am trying to simulate a Volume Control Circuit in PSPice Student Edition. I am unable to see a smooth sine curve at the output. Could you check my circuit. Find the Schematic below Thanks
66 views

### Voltage across Capacitor and Inductor with DC Voltage and Current source

As we know, capacitors and inductors are most important components in circuit design. I am just curious about how they will behave when connected across voltage or current source as per below image ...
50 views

### Understanding id-Ugs and id-Uds graph of a nMOSFET

I'm so sorry posting such a horrible-looking picture, but I really cannot found pictures similar to it online and/or in English! If you found one, please let me know and I'll replace it immediately! ...
68 views

### Ambient LED Project

I'm working on mounting LED strips to my entertainment set up and part of it involves mounting strips to the back of my TV. I want to power the LEDs via a USB port found on the back of my TV. I'm ...
93 views

### How does logisim differ from redstone and real life circuitry?

I recently developed an interest building circuitry systems. It started in Minecraft and then grew when I picked up a micro controller from Radio shack to build an RC car with. Obviously I'm most ...
88 views

### When do I need a resistor during LED flashing? [duplicate]

My goal is to flash a few white LED in serial using 9V battery. Here are the specifications of this LED. As I saw the Forward Voltage is 3.4V, but what does it really mean? Can't I plug this LED ...
104 views

### DUO LED controlled by one MCU pin

I'm having trouble controlling red/green LED. I need to control it from my MCU with one pin. The pin can pull-up or pull-down and the LEDs can be with common cathode or anode. I'm flexible on that. ...
77 views

### Complex number $e^{jk\pi} = (-1)^k$

I know that $e^{jk2\pi}$ or $e^{\mathrm{integer}}$ will give you 1, but I can't find the proof for why $e^{jk\pi} = (-1)^k$. Can someone please explain how $e^{jk\pi} = (-1)^k$? Does it ...
65 views

### Sensing a touch of a metal

Assume there is a piece of metal. I would like to identify, with a microcontroller, if another metallic object is touching this piece. I want to apply this for a smart hook that "knows" if a ...
101 views

### Transistor delay switch equal to a SPDT Relay

I have a circuit I need the functionality of a SPDT switch that is flipped a couple of seconds after power is applied. It is just switching data lines on a USB port so there is no current being ...
131 views

### If this element is unidirectional or bidirectional ? (see the image)

Below the I-V characteristics of two elements .Is these elements are unidirectional or bidirectional ?
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### questions about open circuit, pull up resistor and MOSFET selection

Please let me ask 3 questions about meaning of open circuit, calculation of pull up resistor value and selection of MOSFET. I'm trying to understand how to use the TPS3808G33 reset IC and the ...
63 views

### Can a COTS FM Radio transmit?

This is probably a really silly question, but I still want to know... Given a standard off-the-shelf FM radio alarm clock, what is to stop it from transmitting radio waves when physical motion causes ...
44 views

### Kirchhoff law in Electronics Workbench

I have a task to check Kirchhoff laws in this circuit. If I understand everything right, I3 + I2 should be equal to I1, but it isn't. What's wrong?
59 views

### Is there a limit at the voltage you can apply to a transformer primary?

I have a 9v transformer but all it says is that, there is not info on the primary. The voltage supplied to my house is 120v. So, the transformer will just lower the voltage by a 0.075 factor, ...
1k 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 ...
203 views

### Why does a resistor reduce voltage if V=IR? [duplicate]

I'm sure this is a very simple question, but I have been confused about this topic for a while now. According to Ohm's law, resistance varies directly with voltage. This means that if resistance ...
39 views

### How a solar charge controller can work on both 12 volt and 24 volt

Please excuse me for my silly question, I have basic understanding of electrical circuits. I came across a solar charge controller which was rated for both 12 v and 24 v. My understanding is that ...
102 views

### Power rating for opto-triac trigger circuit resistors

RHS will be using 220v 400watt bulb 2 simple questions 1- does the 360ohm resistors has to be of high watt too ? 2- all i can find is 5-10watt resistors, can i use them ? would they snub correctly ? (...
136 views

### Pull Up/Pull Down Resistor Confusion

I have googled the crap out of this but I can never find a good answer. In a circuit with a pull up resistor, why is the input pin fed current with a resistor? A pull down resistor circuit doesn't do ...
79 views

### Is a Van de Graaff generator a voltage or current source?

I'm currently studying basics of electrostatics and this question comes to me as any generator must be from either of the two types but which is the fact I'm not able to justify which. From its ...
85 views

### What are limitations of Kirchhoff laws in presence of A..C current.what are the bounds on its application in such case?

I'm not able to understand while Kirchhoff's laws seem to be based on very fundamental logic they are still not applicable in some cases. I tried to look for answer in text book but got no clear view. ...
437 views

### Understanding current, voltage and resistance

I'm still trying to wrap my head around current, voltage and resistance, and slowly I have the feeling that I start to get some things. Hence, I would like to describe my understanding so far and ask ...
102 views

### Should HDL languages be taught before software languages? [closed]

I'm a Computer Engineering student and learned the basic sequential programming languages (C/assembly/Java) way before I was even introduced to HDLs. Thus, my whole programming logic was based upon ...
611 views

### Why does isolation transformer protect from shock?

Perhaps I can best explain the question with two examples: (1) there is PC powered directly from 230V mains (unprotected by RCD or similar), and there is fault in PC that causes line voltage to ...
509 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 ...
57 views

### Having trouble with light activated circuit.

R1 = 10K 1/4W Resistor R2 = Photoresistor (any type) R3 = 2M2 1/4W Resistor R4 = 1M 1/4W Resistor C1= 10µF 25V Electrolytic Capacitor C2 = 100nF 63V Polyester Capacitor D1 = 1N4148 75V 150mA ...
99 views

### Voltage reduced when using NPN transistor

I'm currently trying to reverse the voltage at a DC motor ports, from 5V to -5V, to invert its rotation. I also want to be able to have 0V at theses ports. I have a micro-controller that is able to ...
118 views

### Why do LEDs need resistors and lamps do not in a series circuit [closed]

Obviously a basic question but unbelievably difficult to get an answer I understand that LEDs are diodes and that if you don't limit the voltage to a LED it will blow because it draws as much current ...
27 views

### How to determine total circuit voltage and individual component resistance for a series circuit

This is a question from someone who has just started to learn electronics. I'm a bit confused Lets say I have a series circuit with three lamps. Lamp 1 needs 1V, lamp 2 needs 2V and lamp3 needs 3V. I ...
140 views

### What is an n-by-n matrix in a series-parallel circuit?

I started reading a textbook about basic electronics and I reached a section about series-parallel circuits. Here is an example of a series-parallel circuit: simulate this circuit – ...
84 views

### How do logic gates operate? [closed]

I know what the major logic gates are, I know that each gives a different output depending on the input. However, that's all I've been able to find. Every time I look it up, its a list of gates and ...
This is Class A amplifier I trying to make up to 5 Watt output for 8 $\Omega$ load. Is this amplifier circuit OK?t gives about 800 mW out on 8 $\Omega$ load.