# Questions tagged [resistance]

A measure of how much a conductor opposes current flowing through it. It can also refer to a part of a circuit, which has a non-negligible resistance value.

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### Alternating current complex resistance

I am preparing for an exam and I am stuck on this task and cannot get any further. I would be very grateful for tips and advice. Thank you in advance. Here is the task: Two real coils connected in ...
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1 vote
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### Resistances to two batteries where the bat1_pos + bat1_neg = bat2_pos + bat2_neg? But, bat1_pos is shorter than bat2_pos

SOK makes a unit called "12-Slot Outdoor Insulated Battery Rack – Fits SOK & EG4 Batteries" In this configuration there are two batteries next to each other stacked six sets deep. Both ...
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### How to design digital rheostat that can handle 100 mA?

Specification: Bidirectional current Output current: 1 uA to 100 mA Terminals common-mode voltage: +/- 12V That would be 24 Meg to 240 Ohm if that is possible. Stability: +/- 1% if possible Bandwidth:...
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### Why do I have to increase the current by 2V when I am using a transistor?

I have a 3V 3W LED, which I would like to control with an ESP32. For controlling the LED, I have chosen a TP122 transistor. Here is my 'schematic': (The Arduino is an ESP in real life, and the 3 V ...
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### How do I create a circuit to reliably calculate a range of unknown resistances?

I'm designing a low power circuit which serves to determine the unknown resistance across a 16 channel sensor. So far the results are bit subpar. The resistances are a function of a different applied ...
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### Testing to find polarity of PCB power connector

I've got a PCB I ordered from China. It required a 5V input voltage through a barrel jack. The issue is there is no sign showing the polarity (positive or negative center) so I don't want to connect ...
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### Why is there a sudden drop at the rest initial point after discharging? (trying to find IR Drop of LIC)

I'm trying to get IR drop of one of my LIC cells. After discharge, at the initial point of rest, I believe there should be a sudden increase in the voltage due to resistance. Does anybody know why is ...
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### How to find current for Thevenin equivalent circuit

I'm trying to figure out how to calculate the Thevenin equivalent circuit for a voltage divider like the following one: I understand that V_th is obtained by opening the terminals of the output, so ...
1 vote
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### Soft-start circuit for highly resistive load - negating initial voltage spike

I am trying to design a soft-start circuit for one of my projects which has a relatively large resistive load (~1MOhm). I found the following example circuit from an answer for a previous post (12 V ...
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### LCR meter U1733C - R range mesurement

I have the LCR meter "U1733C" and I am little confused about the "R" scale. As I understand (the manual doesn't say it clear - maybe it is self-evident and I am missing something) ...
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### Resistance Vs Reactance Definition

I am trying to understand the practical distinction between resistance and reactance. As I understand from all what I read the resistance is responsible for the current flow and the reactance is ...
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### Find equivalent resistance of a resistor circuit [closed]

what is the process for finding the equivalent resistance of the following circuit?
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### Why does a line-tester glow more when I touch the steel door frame?

I reassembled my line tester, and it was then that I got to know how it actually works. I know that when someone touches the metal part at the top, the neon LED inside glows. However, I have seen that ...
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### Trying to understand (and mimic) the multimeter's interference with a circuit

I am trying to use a microcontroller to regulate the speed control of a sewing machine, rather than the foot pedal that normally serves this purpose. The pedal cord has 2 wires that connect it to the ...
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### Find R value from capcitor discharge plot obtained using scope

I'm using an oscilloscope with probes that are specified to have to have an input resistance of 10Mohms, I apply 5 volts (using power supply) in parallel to my capacitor and use the scope in parallel ...
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### Total Resistance

How can I calculate the total resistance in each circuit, assuming that every resistor has the same resistance? Are the diagonal resistors in parallel? I do not have any idea, so every kind of help ...
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### Adjusting underfloor heating thermistor resistance to match a different controller

I have DeviMat underfloor heating installed in my bathroom, presently matched to a Danfoss DeviReg "smart" thermostat. There's a matching Devi heating probe installed under the floor which I ...
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### MCAT resistor question

Example: Consider two resistors wired in parallel with R1 = 5Ω and R2 = 10Ω. If the voltage across them is 10 V, what is the current through each of the two resistors? Solution: First, the current ...
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### Why do I measure different resistances in the same wire at different current levels?

I've been doing some testing recently on the resistances of various pieces of aluminum for some applications. I've been measuring the resistances of these pieces by passing a constant current through ...
1 vote
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### How to find Thévenin voltage with dependent voltage source

I am not an electrical engineer, so I lack fundamentals. I was trying to solve for the Thévenin voltage, that is Vout at the open terminals A and B, but what makes it significantly difficult for me is ...
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### calculating total current consumption before and after voltage regulator

I have a simple circuit. IC1 is a standard 7805 voltage regulator. Let's assume the battery G1 is 10 volts and all LED's each have 1V for its voltage drop. Do I calculate total current consumption as ...
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### How do I get sheet resistance from my hall sensor model? Do I just put in that formula? If so, how do I put 'ln' and 'pi' in?

How can I achieve sheet resistance in my hall sensor model? How do I input that formula in to get that output graph? Any feedback helps, thank you. I am referencing from this paper. https://www.mdpi....
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### Best approach for heating small lengths of nichrome at 220 volt

I got a length of 5 meters of Nichrome wire from a toaster that works on 220 volts. Its rating is 800 watts and its specific resistance is 12 ohm/meter. For my small oven-project, I only need a half ...
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### Removing turns from a relay coil to make it work on a lower voltage?

I have a piece of machinery that was moved from a building with 240 V to a building with 208 V and all is well but the contactors don't seem to pull in all the way. Could I remove enough turns from ...
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### In Proteus 8 how do I know if current on a component is too high?

This kind of setup should at least warn me about the current on the LED being too high. When I'm going to build something in real life, how can I be sure I don't need resistors here and there? Maybe ...
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### Can we make 300 ohm 300 watt resistor from three 100 ohm 100 watt resistors?

We have three 100-ohm, 100-watt resistors, but we need a 300-ohm, 300-watt resistor. Can we create a combination to achieve this? We aim to dissipate 150 watts through the circuit. If I connect three ...
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### Why are current, voltage and resistance all low in this scenario?

My understanding here is that compared to the internal resistance of the source, the resistance of a human is very low so terminal pd is also low. Then if current chooses the path of least resistance ...
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Hello, I am trying to find out output resistance of opamp. Is the way that put the small signal model source at the output, set the voltage at operating point 0.9028V, and set the AC amplitude for 5mV....
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### Measuring the resistance of an LED -> getting conflicting values

I couldn't find the resistance values for an LED so I tried to measure it and ended up much more confused than before: I have a plain (red) LED and initially I used a multimeter to measure the ...
1 vote
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### Help verifying answers on solving $i$ using superposition method

The problem in question Need help on verifying answers.   For the first voltage source, I combined resistors that are in parallel with each other. i = 12 V / (1.714 ohms + 1.875 ohms) = - 3.343 ohms (...
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### Max voltage per pin when measuring differential voltage with MCP3422

Im measuring differential voltage over a 1 Ohm (shunt) resistor at max 1 Amp, load voltage is 12V DC using one of the channels on MCP3422. MCP3422 is powered from 3v3 DC. The datasheet https://ww1....
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### How to best relate a case temperature measurement with the actual junction temperature?

If I have 4W of power dissipated through a transistor (as derived from measured current and the datasheet's on-resistance) and I measure 40 deg. C on the case of the transistor, what is the best way ...
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### Two-point probe volume resistance how to measure without guard?

So I have measured the surface resistance of a highly insulative material using a Megger MIT 420/2 and a two-point probe. But how would I go about measuring volume resistance? The Megger has no guard ...
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### If i know a battery's internal resistance, how accurately can I predict its maximum current?

Is my thinking on the right track? Say I have a AA battery that the manufacturer claims has an internal resistance of 0.5 ohms. Can I say that the maximum current ... i=\frac{v}{R_I+R_L}=\frac{1.5}...
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### Equivalent resistance of a network

Determine the equivalent resistance across the terminals $a-b$. I placed a $1V$ battery across $a-b$ and then used mesh analysis on $4$ loops which resulted in using $4$ equations. But is it ...
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### How to do an electrical network analysis?

I'm preparing for an upcoming exam in electrical engineering and came across this task. My question is: Which method is best for this? I think the superposition principle would be very complex, right? ...
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### The resistance value for PWM circuit uses STM32F103C8T6 and MOSFET

I want to design a PWM circuit using STM32f103C8T6 and MOSFET as shown below. I use MOSFET IRF3708 because Gate-to-Source Voltage low. but low power. MOSFET IRF3205 has a large power but Gate-to-...
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### How to determine equivalent resistance between terminals?

What kind of symmetry I can use to get the result? I think I have to redraw a circuit, but how?
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### Heater circuit using series resistors

The subject seems to be very easy and simple but performing research and looking at the real devices I get more and more questions. Let's take this article as a basis. It has the following circuit: ...
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### Calculate resistance between 1 and 2

I am preparing for an electrical engineering exam coming up and I got stuck on task C, where you have to determine the resistance between 1 and 2. How do you do that exactly? I have already solved ...
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### GPIO voltage drop

I have the following problem. I have a 3 V line that comes from an electronic drums controller that goes into a pedal through a mono cable (TS). The tip has +3 V and the sleeve is GND 0 V. When I ...
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### Symbol of short circuit (or termination) with an Earth

Can someone explain to me why the symbol of the valve arrester has a short circuit, if it is already earth? I don't understand why it is depicted like this. Why does the valve arrester have the symbol ...
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### Can the formula for calculating the resistivity be used to know the length of a coil of wire?

I am bamboozled after I found that the length of a primary coil of a transformer that I wanted to recoil was approximately 870m. The wire used was about 0.4mm in diameter, the coil as taking a voltage ...
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### Dimmer + LED light bulb + resistor = Ohm's Law Broken

CIRCUIT: A 12 volt battery powers a dimmer. The output of the dimmer powers 4 LED light bulbs. They are all in parallel: 6W + 2W + 2W + 2W. The 6W bulb is a spotlight. The 2W light bulbs are under ...
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### Same power in the circuit comparison [closed]

I have 2 circuits with the same power (900W), could anyone please explain the big different between these two? Circuit one has 30V, 1 Ohm, 30A and 900W of power. Circuit 2 100V, 11 ohms, 9,09A, 900-...
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### Does the minimum value of the S11 (return loss curve) at the resonance frequency depend on the resistance of the antenna?

I was trying to fabricate a flexible NFC antenna. Initially, I fabricated my design on a copper PCB. It worked perfectly fine with my NFC chip and facilitated NFC communication. I observed its S11 ...
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### Art of Electronics - Confused about Zener Diode voltage formula

Working through Art of Electronics and the section on Zener diodes confuses me. There's another question about this section on the site (Art of Electronics - Zener Diode Example), but I'm still ...
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### Circuit current flow

I have a question which might be somewhat classed as newbie but I may have massively overlooked this concept and changes my understand greatly if true. Looking at the image, the voltmeter measuring ...
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### Power schematic questions

I received a guitar pedal in poor condition and looking to repair. Checking through the schematic, it appeared the electrolytic caps were installed backwards. All other picture I could find online ...
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### HOW TO FIGURE RESISTOR WATTAGE

I am trying to understand how to figure a resistors wattage based on label.