# Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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94 views

I tried calculating it on my own and end up questioning why 200k * e^-10 becomes .908 W instead of 9.08 which was what I've calculated
138 views

### Understanding RF amplification

as general interest I am trying to learn a little about RF, antennas and signal amplification, largely in the context of 2.4 GHz. I have read about two DIY projects that informed me somewhat: This ...
70 views

### Mapping two buttons press as a 3rd button

I got a cheap controller with only 5 buttons. I thought about soldering a few more in parallel so that pressing any of the additional buttons would trigger some other two buttons simultaneously. Then ...
132 views

### So why do battery chargers need two prongs? Why not just one? [closed]

Electricity flows from area of highest electric potential to lowest, I get that. What I don't get is why any battery charger would use two prongs on an outlet (or a few other items of similar purpose)....
59 views

### How does this RS-latch with open switches power the lightbulb?

So I'm trying to learn some of the basics in electrical engineering such that I can better understand how computers work and I'm currently reading about circuits with switches, relays, different gates ...
178 views

### If energy is drained from a capacitor linearly, does capacitor voltage decrease linearly as well?

If a charged capacitor is connected to a current source and resistor as shown above, the resistor is constantly consuming 0.001J/s. If you were to make an energy-time graph of the capacitor, you would ...
1k views

### Calculating energy absorbed by an element

I need your help to understand the solution to the given question where energy absorbed needs to be calculated with the given graphs of the current and voltage through the element. Please help explain ...
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 ...
2k views

### nodal analysis, current direction

Right, first the diagram, I tried using the schematic function,but it never actually added the schematic. I picked this because it illustrates my confusion in the simplest schematic I could find. We'...
243 views

### What Resistor to use between Source and an IC

I'm trying to make a clock, and as part of that I need to power some IC's. To give a specific example I'm looking at the TI SN74HC163 4 bit counter. After some searching around, I found myself ...
2k views

### When you connect two batteries in series, why doesn't the middle short?

When you connect two batteries in series, why doesn't the middle short? The connection between the positive terminal on one battery and the negative terminal on the other battery has no load, so ...
48 views

### Why does no current flow when GND of one battery is connected to VCC of other battery? [duplicate]

I have enough experience with electronics to design and solder working circuits. I never quite understood though why circuits must be closed for current to flow. I alway understood electrical current ...
57 views

### Infrared Receiver - Simple questions regarding data sheet and basic electronics

I've purchased a 36 kHz IR receiver (TSOP38436) but I'm still learning about electronics and I'm not sure how to connect this to my micro controller (Arduino). (Also, I'm using 36 kHz instead of the ...
185 views

### Does resistor placement change power dissipation in simple LED circuit?

Does the power dissipation in an LED and resistor change depending on the resistor placement? Let's assume the following: Supply Voltage: 3.3v (DC) LED Forward Voltage: 2.1v Resistor: 330 Ohm I ...
170 views

### Kirchhoff Voltage Law in a two port network

In a tutorial about h parameters of a two port network, I find the below snippet in the image unable to grasp. According to KVL, the total voltage in a loop is the algebraic sum of the individual ...
772 views

I'm trying to understand how the charging of a plate capacitor works which lead me to question my understanding of current flow. In many explanations, it is said that the voltage source pulls the ...
76 views

### How can I determine the output in this circuit? [closed]

I have such circuit: simulate this circuit – Schematic created using CircuitLab Vin is either equal to Vcc or to 0. How do I go about determining Vout?
184 views

### Finding phase shift between the voltage and current

I am trying to find the phase shift $\phi$ of this circuit. I am using the formula: $$\phi = arctan{\frac{X_{L}-X_{C}}{R}}$$ Substituting in the values: \phi = \arctan{\frac{2000\Omega-4000\...
44 views

### 2 Possible Currents and Vdrops from same Resistor: Which Will it Be? [Beginner]

simulate this circuit – Schematic created using CircuitLab Let's say I have a power supply that supplies 5v and 3A. If I add a 2 ohm resistor, it could do 2 different things. Realizing that ...
968 views

### How to determine the steady state voltage across two capacitors in parallel

Say we have two capacitors C1 and C2, initially isolated from each other and each having an initial voltage Vc1 and Vc2 respectively, where Vc1>Vc2. When suddenly connected to each other in parallel, ...
72 views

### Arduino pin connection basic

In the Arduino Uno's basic manual, connections for fading led are given. They have connected led on breadboard. The positive of led is connected through a resistor to the pin no 9 (pwm) and negative ...
69 views

### Basic circuit - valid pulldown

I am trying to create a circuit with multiple 5V logical control lines pulled down with 10K resistor. Is the below circuit the right answer? I can't help but feel like this will create a short ...
62 views

### How does a circuit regulate current in response to a lower voltage?

Brief background, I studied physics in college and am learning EE on-the-job through Art of Electronics and this wonderful website. So this is a follow up to a previous question I submitted here ...
70 views

### Basic questions on biasing

I have some trouble understanding a basic concept. Here is my question. This is from a document which can be found on the website, http://www.ti.com/lit/ug/tidu765/tidu765.pdf The text ...
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 ...
111 views

### Voltage Drop doubt

In an ideal circuit with just a battery short circuited, where there is no resistance in the wire, why is it necessary to have resistance along the way? I understand Ohm's Law, and that the current ...
163 views

### Why did Adafruit pick a 10K resistor for this phototransistor breakout?

Adafruit has an ALS-PT19 Analog Light Sensor Breakout. It looks like it has a 10K resistor on it: The ALS-PT19 datasheet says that resistor is to convert the output current of the transistor to ...
73 views

### How do I determine the capacitor to use when converting current to voltage?

I'm trying to figure out how to use an ALS-PT19-315C/L177/TR8 phototransistor (or something like it). The datasheet has this sample circuit for converting current to voltage so that I can measure it ...
61 views

### How do current and voltage relate to load?

I think I've lost the plot somewhat on how current and voltage relate to the load in a circuit and I'm hoping for some really basic level clarification. In fact, I'm not really sure how to ask the ...
60 views

### Why doesn't current leak to ground (DC)? [duplicate]

In the circuit shown below, I am considering ground to be ideal earth ground (stays at 0V no matter how much current it absorbs). It is my understanding that current flows when there is a potential ...
130 views

### Possible reasons for differences in voltage between garage opener circuit and Raspberry Pi

I am attempting to use my Raspberry Pi's GPIO to activate a garage door opener (specifically Craftsman 139.5364812). As far as I can tell, the garage door is operated by shorting two terminal screws ...
859 views

### A basic question about amps, watts, and charging batteries

Why do we speak of watts (and not amps) when we refer, for example, to the "7.5W Wireless Charger for iPhones," but when we talk about cord-based USB charging, the specs typically refer to amps (and ...
80 views

### monostable Eccles - Jordan multivibrator, theory

I’ve a few problems and questions to the principle of monostable multivibrator’s work. Basic schematic is as below: What is the reason for D1, C1, R3 elements at input? Why I can’t just tie a ...
145 views

### What is the purpose of extra parallel resistor R2

This probably is a very basic question. I looked at a real world device schematic - a "digital pushbutton" and can't figure out why R2 is necessary. This device is supposed to be connected to arduino....
3k views

### Confusion over the power wires of USB (GND and +5v)

I'm converting a battery powered device to be powered off a USB connection. I think I have everything figured out except one thing. I understand there is a GND wire inside the USB cable for power, ...
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, ...
153 views

### Can't understand a given answer about a 1st Kirchhoff's law question

I am currently studying the textbook "Lectures about the fundamentals of Electrical Engineering" by Adalbert Prechtl and after finishing the theory about Kirchhoff's law, I tried to solve some basic ...
817 views

### 741 Op. Amp.: Inverting input connected to output (pin 2 connected to pin 6). What does it mean?

simulate this circuit – Schematic created using CircuitLab I am a newbie electronics students. My question is, what does it mean (what happens) when you connect pin 2 to pin 6 on a 741 op. ...
49 views

### How can I solve for impedances if given RMS currents?

Given a very simple circuit such as this. If I where given the RMS values for the three currents, how could I go about solving R and Xl? (the resistor and inductor in paralell) I know I can not ...
367 views

### how to wire together multiple photoresistors to make one big sensor?

I'm using an esp32 dev board, and a bunch of 5v laser diode emitters pointed an equal number of photocell resistors across a plane. The goal is only to detect when any two or more beams break at the ...
81 views

### Bjt for trigger MOSFET

I my project MOSFET need 13 v 65% PWM to trigger but controller output is 5 volt then how can I amplify this in voltage
273 views

### Maximum output power of a PA

I was discussing with a friend about maximum output power of a (class A/B power) amplifier (for example if the device following the PA can only tolerate a certain amount of power). If the input power ...
69 views

### Source transformation violation

Using thevenins or norton theorem, we can easily find current through the resistor as 1 amps. But if we convert the current source to voltage source , current turns out to be zero amps . Why?
61 views

### I need help finding the equivalent resistance

Hello guys , i'm new in the amazing world of electronics , and im very confused with this circuit . Im supposed to find the Req (equivalent resistance , but dont know how in this specific circuit), ...
235 views

### Basic question about conduction current

Sorry for my english and long post again. After reading this article, I realized that my understanding seemed to be wrong. I thought that to create conduction current in some wire first we need a "...
218 views

### why does a fuse break when a wire is connected to ac socket directly

I connected ends of wire to ac hot and neutral points of ac outlet sockets - an electric fuse broke and power went off in my house. I understand this happened since there was closed circuit ...
3k views

### RS485 to RS232 conversion?

I need to connect a sensor that uses a RS485 transmission to RS232 or something I can read through the com ports on my data logger. I can't use usb ports or virtual com ports due to the program I am ...
243 views

### How do you model a “leaky inductor”?

My understanding is as follows: A voltage induces an electric field at a capacitor, which is measured in coulombs. If I wanted the capacitor to leak the charge exponentially, I could model that as a ...