# Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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### How do I use ideal MOSFET model in LTspice? or How do I set voltage in node without voltage source?

I want to simulate the principle of 1T1C DRAM cell. But if I model voltage source in Bit line, bit-line voltage is set by its input signal. So I want to seperate bit line, using ideal MOSFET component,...
1k views

### How is he not shocked? [closed]

I'm new to electronics, and I can't make sense of this video. At the 9:10 second mark, he holds a metal spoon across the ends of a wire that's carrying around 100 amps, and he's not harmed. Later the ...
• 51
137 views

### Confused about usage of Ohm's law & Kirchhoff's laws to solve a circuit

I'm solving this circuit using Ohm's law and Kirchhoff's laws: I solved the circuit correctly the second time. Equation A: $$I_1-I_0-6=0$$ Equation B: $$-120\ \mathrm{V}+I_0\cdot 10+I_1\cdot 50 = 0$$ ...
• 13
79 views

### Understanding reference levels in circuits

I understand that a zener diode uses its anode as a reference to limit the over-voltage levels that appear on its cathode. However, in the circuit shown below, I am confused about why the anode of the ...
• 117
2k views

### LED Fails to illuminate, what am I not seeing in my configuration(s)?

I'm working on a super simple circuit, I want to light the LED. Power Source 1: 5.5v from 9v battery through breadboard power supply module Power Source 2: 5.5v from lab bench PSU LED Info: Vf - 3v to ...
• 181
107 views

### Asymmetric LC tank with diodes

Is there a circuit that can produce an asymmetric wave, where some parameters of positive and negative half waves are different, such as voltage amplitude or time? Intuition says that we need a ...
3k views

### Why did current increase when voltage decreased?

I was taking a short course on home electronics (mostly just how to safely change sockets, switches, and bulbs) and the instructor told an anecdote about how when the energy company accidentally ...
• 151
188 views

### Can you explain why doesn't current always go through the first part of a parallel circuit (without water or heavy math)? [closed]

I have tried to understand this over and over. I don't understand how current ever makes it beyond one branch of a parallel circuit. I apologize for the circuit if it doesn't make sense. I simply do ...
331 views

### How does electricity transfer energy?

I am new to electronics and was just looking for some intuition behind how electrons give energy to components. I have been attempting to understand this under the condition of voltage being the ...
• 9
91 views

### Connected negative contacts of 2 supplies [duplicate]

When the negative contacts of 2 power supplies are connected with a wire they share the same base potential that can be associated as GND. But why does this happen? For me it's a bit magical that the ...
• 149
1 vote
59 views

### Mix of power supplies

I am struggling to understand what happens when two power supplies are connected: Both supplies build a whole circuit, the rest of the second supply is left out for simplification Both power supplies ...
• 149
1 vote
115 views

### Voltage distribution with two batteries [closed]

I have a question regarding a simple circuit of two batteries (9V) in series with a single resistor connected to the outer contacts to prevent a short. When I'm simulating this circuit, a current also ...
• 149
68 views

### Is passive sign convention the exact oposite of active sign convention?

I'm currently studying the fundamentals of electrical circuits. For my studies, I'm using the book "Fundamentals of Electric Circuits 5th ed." In the introduction chapter, section 1.5 Power ...
100 views

### Which is the correct flow of current in these following circuits for nodal analysis?

My professor told me one method, a well known and trusted youtuber told another method and our assignment solutions have another method for nodal analysis so I can't figure out which method is ...
94 views

### Step response v/s DC voltage

I have to find step response for this circuit considering my input as Vo and step for Vin( I am using Simulink for this) Firstly what i did was making this circuit (DC voltage is 1V) The response on ...
285 views

### Thevenin/voltage logic

So, I'm trying to find the Thévenin voltage of this circuit. I understand that the resistors (R+3R) by node a are irrelevant as there's no current running and thus no voltage drop. However, I'm a bit ...
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1 vote
117 views

### Confirming behavior of a diode in an open "circuit"

I have built the "circuit" illustrated below. Basically its a 5V supply with positive terminal connected to a schottky diode's cathode, multimeter in voltage measurement mode across the same ...
1 vote
146 views

### Why is this oscilating circuit not possible [closed]

In my mind, this circuit should oscillate because the transistor draws the entire power when turned on. This, in turn, should cause the base to turn off, opening it back up and continuing the cycle. I ...
1 vote
71 views

### Can a transistor replace a switch that closes ground to an input?

I've been browsing on Google for quite a bit now but couldn't find an answer. I have a remote that triggers the shutter of a digital camera. According to the schematics that I've found, the ...
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1 vote
63 views

### How to set current on a cvcc?

I got a cheapo cvcc off ebay. Setting volts is pretty easy. I just hook my multimeter leads to the output and twist. But, how do I set amps? I need something to dump the current in. What should I dump ...
74 views

### Questions about a CTAT circuit

Please refer to the following CTAT circuit source: https://wiki.analog.com/university/courses/electronics/text/chapter-14 The following notations are used: VR1 - voltage across resistor R1 VR2 - ...
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1 vote
71 views

### An active inductor connected to an inactive inductor in series

I am a grade 12th student studying about inductors and RLC circuits for the first time. While studying I got stuck with the idea of an active inductor being connected to an inactive inductor. ...
98 views

### How to read circuit diagram [closed]

This is a basic question but I am a little bit confused on how to interpret this diagram. What are the symbols that are present in this diagram? What happens when there is current running through the ...
• 13
96 views

### An old 9 V inverter circuit

I wanted to discuss and ask questions about an old inverter circuit I built 15 years ago when I was studying; the circuit was powered with an ordinary 9 V battery-Duracell type, and steps the AC ...
52 views

### Help On Dual Amplifier Design

I am pretty new to electronics and so far, have been teaching myself and designing things with the help of the internet. I made and designed a class-AB amplifier circuit that drives two 8-ohm speakers ...
85 views

### Choose the RLoad resistor for zener diode

I need to calculate the Rload resistor range for the operation in this case: I know that many times to calculate the Rseries but now he is given, how does my teacher expect me to calculate the RL? ...
• 411
214 views

### Where does the current applied to the gate of a transistor "go"?

In the following circuit, the LED lights up: I was afraid I'd misuse the transistor symbols, so I just drew a box to make sure I communicated the right thing. This is the transistor, G/D/S means Gate/...
• 143
99 views

### Why is my transistor is letting through current?

I'm working my way through the Arduino starter kit project book and am doing the first project involving a transistor (MOSFET). As far as I understand, what I've done is wired up a 9V battery, a ...
• 143
481 views

### Understanding how the input pins on my Arduino Uno read voltage

I recently bought an Arduino starter kit which comes with an Arduino Uno and some components. I know very little about electronics or physics. The Arduino has some analog-to-digital pins on it which ...
• 143
50 views

### If there is a ground potential (V = 0), is there a ground current?

Can current be defined with respect to some "ground current"? If so, how?
• 1,526
132 views

### Movement of charged particles in gasses or vacuum

Electrical current can be formed inside gasses and even inside vacuum under certain conditions. The charged particles that form the current there are positively and negatively charged ions and ...
1 vote
361 views

### Where does current go when current is flowing dividing between two branches, one with a diode, one with resistor?

This question applies to both images in circuit, but for sake of clarity lets focus on image (b). Assuming both diodes (D1, D2) are ON (forward bias) and assume both diodes are ideal diodes. I tried ...
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1 vote
531 views

### How do I calculate current flow through a capacitor?

Currently I've only worked out on the time constant and Vo(t). Time constant = RC = (4500 + 1500)×(10 μF) = 0.015 s = 15 ms Vo(t) = 24×(1500/{4500+1500)) I used the voltage divider rule in this case, ...
81 views

### Smartifying simple USB lamp with ESP8266 / Voltage regulation 3.3 V <-> 5 V

I am a complete beginner and my electrical knowledge back from school is basically non-existent anymore. I have discovered the ESPHome project and am amazed by its simplicity, so I wanted to turn a ...
1 vote
109 views

### Output current/voltage for PIC12F675

I want to get some clarification about output current and output voltage from a PIC12F675. As I read in datasheet, max. current for an output pin is 25 mA. Is it always 25 mA, or will it depend in ...
• 67
730 views

### Is there a simpler solution for this kind of priority switch? (a teaser for the holidays)

Somebody taught me this circuit in my childhood and I haven't forgotten it ever since. If you close SW1 first, Lamp1 will light at full brightness, then if you turn on SW2, both Lamp1 and Lamp2 will ...
• 53
359 views

### Connecting a capacitor to a voltage supply in series without a resistor

When connecting a capacitor directly to a voltage supply (without a resistor), is it correct to expect a surge in current at the instant when the capacitor and the battery are connected, then current ...
• 377
79 views

### Avoiding power drop in LED strip lights

I am wiring a van and will be putting in ~25-30 feet of LED (RGB+W) strip lighting. My main power supply is a 300 Ah, 12 V battery. I am familiar with LED strips, dividing and connecting them, but I ...
198 views

### Basic AC circuit analysis with wattmeter data

I am having trouble dealing with this exercise. The data given is: UG=90V, ω=190rad/s, V1=0V, V2=35V, W=900W Power factor=1. Being the power factor equal to 1, I can get the current intensity using ...
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923 views

### Mental model for non-real power

In Electroboom's "How to turn an LED On" video he mentions that (ideal) capacitors do not consume real power. I was trying to reason through this and would like to gauge the accuracy of my ...
47 views

### Representation of any signal using unit signal

I was introduced to the unit step signal and told that we can write any discontinuous signal in terms of the unit step signal to omit the discontinuity from the mathematical expression. So if we are ...
1 vote
351 views

### How do transformers comply with Ohm's law and KVL?

I understand how to use a transformer in practice, and I know that transformers obey the law of conservation of energy, but I'm confused as to how step-up and step-down transformers obey Ohm's law and ...
113 views

### Basic question about 3-phase motor in Y connection

I am a electrical technician but in school I dealt with mostly DC (electronics) stuff and programming and now at my work we do mostly 3 phase motors so I would like a better understanding of some ...
467 views

I am not the most knowledgeable when it comes to electricity, so apologies if my questions lacks necessary information that is needed to get a good answer. I work with 3 phase electric motors, and I ...
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77 views

### I have 3 questions about current source. I'm confused if the current source gives the final current in a mesh or do I still need to add/subtract

I made up this simple circuit to show my problem. The title says my problem and you can see the three questions in the picture. I need to resolve this doubt so that I can form equations correctly.
505 views

### Is there a need to ground an isolated electrical circuit? [duplicate]

It seems to me that every time there happens an electric shock through the contact with the ground, it happens because there is a difference of potentials between the contact point and the ground (for ...
960 views

### Problem with equivalent resistance

I have a problem determining equivalent resistance of this circuit. The previous assignment had the battery between C and 3R1 resistor, and i knew how to calculate the equivalent resistance. I ...
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2k views

### What is a multimeter at its core?

We know that, thanks to Ohm's Law: If you have an ammeter, you can put it in series with a resistor of known (usually large) value and now you have a voltmeter (after rescaling ofc). If you have a ...
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Today, in class, we were to analyze this circuit: simulate this circuit – Schematic created using CircuitLab And calculate $\alpha \in [0, 1]$ associated with R2 a potentiometer. I'm confused ...