# Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

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### Calculating for Load Resistance given a T network in between the source and the load

Problem: Calculate the value of load resistance (Rl) for which maximum transfer occurs. Attempt: What I know is that for the maximum transfer to occur, the load resistance must be equal to the source ...
729 views

### Understanding this circuit with op. amps

I'm studying electrical engineering and I've came to a problem, where I cannot proceed. It's a "simple" task, where we're talking about an inverting op.amp with 2 voltage sources, each 1V, while all ...
156 views

### Figuring out if an led strip/matrix has a short or not with a multimeter

I am relatively new to electrical work, mostly stay on the software side of things. I recently soldered header pins onto a few led matrixes I have. They are 3 wire leds (power, data, ground). I'm ...
122 views

### Basic question I would like to be solved

Can someone please solve this for me, telling me what's the right option and why? I will translate for you the question: "What is the reading shown by the voltimeter inserted in the circuit of figure ...
2k views

### NTC 5d thermistor and how to use it

I bought a random thermistor for a circuit I'm planning to build and it turned out to be a NTC 5D-15. I'm trying to build this test circuit: After doing a bit of research, that thermistor resistor ...
1k views

### Voltage across a resistor in RC discharging circuit?

Problem: An RC circuit has a time constant of 68 micro-seconds. The capacitor is charged to 14 V. How much is the voltage across a resistor after 136 micro-seconds of discharge? Attempt: What I know ...
709 views

### Current that flows through a 400 watts flat iron connected to a 220 volt power line

Problem: Find the current that flows through the filament of a 400 Watts flat iron connected to a 220 volt power line. Attempt: The only formula I could think of that will connect voltage and current ...
72 views

### Strange issue with custom 18650 tester

Ive made my own 18650 cell tester that: Fully charges -> fully drains -> partially charges It takes 4 cells, measured independently of each other. While testing the drain circuits (charging circuits ...
251 views

### Safely wiring AA batteries for consumer Arduino product

How do I safely wire AA batteries to improve an Arduino-like device lifetime? Discussion here in the Forum [1] and the Battery University [2] suggests that using parallel AA batteries could be ...
284 views

### Working out what happens to the brightness of a bulb in a simple circuit

I have been going through some past questions for my exam that is coming up this summer. I have come across this question which I originally deemed to be easy however the more I have looked over it ...
180 views

### What would be logic value of high impedance TTL output connected to LED

Suppose a TTL output in high impedance is connected to a LED, which is also connected to a resistor, which is then connected to ground. No circuit interferes between TTL output and LED, between LED ...
390 views

### How to make the output of a transistor the same as the input?

I'm new to circuits in general but have a basic understanding of it. However, it seems I can't wrap my head around the following issue: (I'm using Tinkercad Circuits for trying out different ...
176 views

### N Mosfet basics

Can somebody explain to me why this circuit will not work? It might be that IRF3205 isn't a great choice for an Arduino but it works for Adam Welch on youtube so it should be possible. Tried it even ...
311 views

### Basic AC circuit analysis w/ wattmeter

I am having trouble dealing with this exercise. The data given is: $U_G=110V, \: \omega=150rad/s, \: V_1=0V, \: V_2=5V, \: W=650W$ Power factor =1. Being the power factor equal to 1, I should be ...
136 views

### Why would this AND gate not work? [closed]

Why would this circuit not work as it is expected to work? The IC used in this is a 7408 AND gate.
54 views

### One PSU powering one high power device & one low power device

If one was to power a (potentially) multi-amp device and an arduino with an external LM7812 12v voltage regulator to a 19v laptop charger (in parallel), would the arduino be safe when the multi-amp ...
106 views

### Basic: Current flow and grounding

I have an elementary question about current flow: If I connect a simple 1.5 V battery to a hypothetical LED of 1.5 ohm and an ideal ammeter, the ammeter would show a current of 1 Ampere and the LED ...
88 views

### Super basic Q: How to regulate voltage in this basic circuit to avoid damaging the heating plate?

simulate this circuit – Schematic created using CircuitLab This is for a teen-level science fair type project. Materials include this 3V-12V generator and this 5V 1W heating plate Goal: 12V ...
146 views

### Determining the voltage of a network branch

[NOTE-This is a not a homework problem and i am not asking anyone to solve it] Recently I have been simulating some basic circuit analysis problems in a simulator to get a better feel of the topic....
1k views

### Reed switch melting closed in simple LED circuit — What resistor to use?

Made a simple circuit with a reed switch, wall power source and LED strip (for a bathroom occupied sign). Worked as I’d hoped at first. But, after a while, THE REED SWITCH MELTS CLOSED--leaving ...
852 views

### How do I find the equivalent resistance of a circuit with a node between each resistor?

I can't make out what's in series and what's in parallel in this circuit. The solution I've thought of so far is to consider R1 in series with R4 and R2 in series with R5. Then, (R1+R4), R3 and (R2+...
106 views

### What are important metrics of high voltage power lines? [closed]

Upfront: I am not an electrical engineer and therefore apologize upfront if I am asking a stupid question. TLDR; What are important / relevant metrics of high voltage power lines that can be ...
7k views

### Need some help building a TL072 preamp circuit

I have an early 70's Magnavox turntable/radio console that I want to be able to plug my smartphone into so that I can use it as an external speaker. I'm plugging into the Tape In input, which is an ...
56 views

### 6v switch to power something much larger [closed]

I feel like I'm making this more complicated than it has to be. If I have a 6v switch like this one, can I use it to turn on something like a 110v ~26A power supply? The current is far too high for ...
437 views

### Current Draw vs Voltage

How is it that by adding more components to a parallel circuit, the current at the root increases with no theoretical limit? Using the water flow analogy, you wouldn't find that the flow could ...
279 views

### Fan not working on motherboard even if same voltage works with batteries [closed]

First of all I want to mention that I have no knowledge electrical field, so please forgive me if I will not be explicitly enough or I lack some terms, but I know no one with knowledge about ...
89 views

### Help Using a MOSFET

I have an N-channel MOSFET, part number IXFH30N50P. I am trying to use it as a switch for a 320V 8100uF capacitor bank. My idea is that I would have a separate, small voltage source, like a battery, ...
276 views

### Is the FET gate resistance counted on the RC time constant?

As I understand, a logic "1" output to an input of another IC can be modeled like this : simulate this circuit – Schematic created using CircuitLab with C1 representing output capacitance, R1 ...
99 views

### Calculate voltage over resistor

I have a problem when calculating voltage over resistor because one method worked for one problem but not the next. I solved (b) like this: $$12-4=8V$$ $$8*\frac{60}{60+20}=6V$$ $$V2 = 6V+4V=10V$$ ...
453 views

### Can a short circuit damage nearby devices? [closed]

This happened yesterday and left me scratching my head. We had a badly built power extension cord in our office. Inside it has 3 wires - live, zero and ground (hope I got the terminology right). When ...
326 views

### LM317T outputs current on Adjust pin with nothing connected between adjust and Vout?

I have a LM317T-based simple circuit and I'm using a 12V battery to power it. I connected the Vin to + 12V and made a constant current circuit as shown here. Now, I'm using a variable resistor of 100k ...
891 views

### Confusion about what should be a simple resistor-divider circuit

I'm reverse engineering a circuit in some industrial equipment, and I came across some curious behavior of the input circuit... The circuit is pretty simple, it is a resistor divider with a capacitor ...
82 views

### Connecting capacitor to the ground and potentials question

I am a newbie trying to enter the world of electronics and currently struggling with getting a good grasp of basic concepts of electricity. I understand that electrons which usually produce the ...
230 views

### How to achieve desired output voltage and current draw from a hot shoe

I have very little knowledge of electronics, although I enjoy tinkering with basic electronics from time to time. If I have a battery of known voltage and I want it to light up a small 3mm led, I know ...
361 views

### Combine two circuits

I want to apologize in advance for any ignorance throughout this post, I'm not anywhere near an electrical engineer. Basically I have a consumer which requires 220v and is not operating all the time. ...
5k views

### How to determine a current is AC or DC by use of analog multimeter?

How can one determine a current is AC or DC by use of an analog multimeter? Or its workaround with rudimentary tools or equipment ?
7k views

### Why is current always measured in series with resistor and voltage is measured in parallel?

In electronics lab, while doing superposition theorem, we were asked to measure the current flowing through resistor and voltage across the resistor. As instructed, we measured the current by ...
6k views

### Resistor is always in parallel to a current source and is always in series with a voltage source, why? [closed]

I have a basic question on electronics. Why is it that typically a resistor is always in parallel to a current source and is always in series with a voltage source? As observed in Norton's and ...
1k views

### Confusion between average and rms calculation for power

I have a DC source where DC Voltage = Vdd and the current supplied by this source is rectified sine wave to a circuit. Now I would like to find the average power delivered by DC source. There are ...
894 views

### Looking for a formula for calculating maximum induced AC voltage in two air coils next to each other

I've got a question about electromagnetic induction. I've already done some research but I'm unable to find the easy solution. I want to calculate somehow maximum voltage peak that will be induced in ...
753 views

### Source follower basic question

I just want to clear my understanding about a basic source follower circuit. Following is the circuit Here is my question: Considering Vi > Vgs(th); Vo = Vi - Vgs. Also Vo = Id*Rs as shown in the ...
1k views

### Basic questions regarding Push Pull stage

I am confused as to how the following circuit will work(????) Lets assume that there is no AC signal and only a DC signal is applied. According to the books this is a voltage follower stage i.e Vo ...
84 views

### I need the explanation on a DMM instruction manual

It's HIOKI DT4211 digital MM In Electrical Characteristics section it states: Rated power voltage: 1.5 v DC x2, use LR6 AA Alkaline battery 2x 1.5v But then... in Accuracy Table section, it states: ...
1k views

### Time delayed deactivation of a circuit

In a simple electronic circuit with a momentary switched LED (or bulb, tube etc.); what can be done to trigger the LED for several seconds before proceeding to break the circuit? In other words; I ...
798 views

### Digital Rotary Encoder — Broken? Or am I misunderstanding how it works?

I apologize if this seems like a fundamental question, but I feel like I'm missing a fundamental understanding about digital rotary encoders, because none of my basic encoders are working as expected. ...
244 views

### How are resistor power dissipation calculations performed?

I'm designing a switching mode power supply to supply 150V at 10mA to a nixie tube that is rated for 150V and 3.5mA. The circuit diagram will be very similar to this design, with the main difference ...
4k views

### If Conventional Current is wrong, how can I trace the flow of current in a schematic?

If Conventional Current is backwards, how do I look at something like this schematic and trace the flow of current? I'd like to follow the design linearly from positive to negative. When the battery ...
86 views

### Is it really problem if 0,3 voltage more than required applied in digital multimeter?

Does it negatively affect if more 0,3v voltage than Power Supply (PS) required by general digital multimeter (DMM) supplied ?. I have a DMM with PS requirement of 2 x 1.5v AA battery and in hand is 2 ...