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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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1answer
40 views

Reading of megohm during ground check

During the check of pins on connector with a multi-meter, one of the pins that goes through the relay to provide ground signal, I am getting 8MOhm (8 megohm). I should not be getting anything on that ...
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23 views

Thermal resistance of Thermal Interface Material

Can anyone please give information how to calculate the thermal resistance of SIL PAD "TSP A2000" from make Berguist. from The data sheet its specified thinness is 0.254mm, Thermal conductivity (W/m-...
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Reducing the circuit

I am high school boy, our teacher gave us circuit and we have to find out the equivalent resistance. . Our professor gave us idea that we can solve this question either by either superposition ...
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101 views

How a circuit get short

I am a high school student learning about the circuit, and how the current choose the path with low resistance, I have seen circuits and how one of the resistance among the other resistance get short....
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Are these 2 resistors in parallel?

So I had a circuit to analyse and I needed to find the equivalent resistor and then I arrived to a confusion. Are R1 and R3 in parallel? Here is the circuit. simulate this circuit – Schematic ...
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lm35 Temperature Reading increasing with Hot-melt adhesive (Calculations check needed?)

I have one question with this topic: lm35 Temperature Readings are not right after sealing with Hot-melt adhesive (How mush has it Soldering max Temp toleration ?) it answered by this (Thanks from @...
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How to change resistance with buttons? [on hold]

For example, instead of using a sliding, rotating knob on a potentiometer, it uses buttons to add or subtract resistance. Is this possible? Would preferably like to avoid using micro-controllers to ...
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1answer
34 views

Cable length and voltage drop in offgrid solar installation

I have connected my Lithium-ion battery pack(11.1v 100ah ) with my Epever MPPT charge controller using 5M length of 8 AWG cable. when i put load which consume around 12A , the charger controller shows ...
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Calculate sheet resistance in finite element method

I have a simulation with several polygonial mesh cells (Voronoi-mesh) and their centers of gravity \$P_i\$, each with its own electrical potential. Every cell has the same height \$h\$ all over. How ...
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Find armature resistance on DC shunt generator

A DC self excited shunt generator has a field resistance of 160ohms generated emf is 420v and supplies a load of 55kw how would u go about calculating armature resistance when terminal voltage is 408v ...
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2answers
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Confused about Thevenin’s Theorem

I have a hard time trying to understand why Thevenin’s Theorem is the way it is. As per the diagram below, I understand why we take our “Thevenin resistance” that way. But as far as the voltage is ...
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36 views

Thevenin Resistance in a op amp circuit

I created this circuit and I am struggling on trying to figure out the Thevenin resistance for this circuit.
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Conductivity of liquids (3D resistor network)

Hi I'm an electrical engineer but have not seen this problem before. I'mn trying to measure/calculate the resistance of a liquid. Background: I'm working on an electronic device that can come in ...
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3answers
50 views

Is the maximum current a resistance can draw limited by the maximum current available (current rating) in the power supply?

Let's say I have a single phase power supply at 100 V and 10 amps at my wall outlet. If I were to connect a very low resistance element (say 0.1 ohms), using Ohm's law I could say the resistance draws ...
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1answer
82 views

How can a light bulb run on different voltages (USA and EU)?

There is a concept in EE I don't understand. In Europe we have a 230 V supply voltage and in the USA e.g. 120 V. Now the thing I don't understand, how can I use my charger( or a light bulb) in ...
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To evaluate equivalent resistance of the circuit by star delta method

How do I evaluate this circuit via star delta method?
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1answer
31 views

ajustable resistance and MP2307

i try to make a current 4.2v with the switching regulation methode as you can see in the attached picture. The problem is that when i ajuste the voltage manualy from the ajustable resistance to 4.5v ...
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Problem calculating fuses

I am calculating a fuse and I'm having a bit of trouble. I have a 12v 2A power supply that I want to protect, so my first thought was to place a fast 250v 2.5A fuse in series so it should blow if a ...
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1answer
55 views

Do transistors naturally have resistance on base, collector, and emitter?

I'm using a circuit simulation app called EveryCircuit, and for the npn transistor settings it has forward beta, reverse beta, base resistance, collector resistance, and emitter resistance. I'm a bit ...
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2answers
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Does a correctly sized resistor protect low voltage components from a high voltage source?

Let's say that I have a 37v DC source that I would like to reduce to 12v so it can run a 12v light bar (a string of 6 leds and I assume a resistor to limit the current). I measure the resistance of ...
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36 views

What is the Rseen from this node?

In the text book I am reading (CMOS Analog Circuit Design by Razavi) the author wrote that the Rseen from node N is (1/gm7), however when I derived it myself I found that the Rseen is ro4 // ro6 (...
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1answer
60 views

Calculating heat generated by resistance wire on 3 phase current

I am designing a heating element consisting of resistance wires coiled around a tube to heat water flowing in the tube. All three heating elements (loads) will have the same resistance and will be ...
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1answer
113 views

Low resistance digital potentiometer - alternatives?

I've done quite a bit of searching online and can't find a solution to this (probably trivial!) problem: I am looking to replace a resistive fuel level sensor in a car, with a solution which can be ...
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Voltage gradient in voltage difference across a resistor

If I have a voltage difference V from terminal 1 to terminal 2 of a resistor. I take an arbitrary point P along the resistor, between terminal 1 and terminal 2, and take terminal 1 as a voltage ...
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8answers
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Why do fuses burn at a specific current?

We usually specify the maximum current that a conductor (such as a fuse) can handle without burning. But doesn't the conductor really fail when a certain amount of energy/heat has been dissipated in ...
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3answers
157 views

How can I realize this nonlinear resistor?

I want to know if it's possible to realize a circuit described by the equation $$I = \sin(w V)$$ where \$I\$ is the current, \$V\$ the potential and \$w\$ a variable which characterizes the single ...
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106 views

What is the circuit formation in this electric blackbox?

It should be a simple question from my exercise book, but I could not find the solution for some reason. As illustrated, in an electric blackbox, there is one switch (k), one 3-volt battery, three 1-...
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3answers
132 views

Why does a pull down resistor eliminate floating input

Ever since I connected a button to an Arduino for the first time, I've wondered how does the resistor prevent floating input from happening? I've read several answers to similar questions, seen videos ...
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My ohmmeters don't behave as the book “make: electronics” describe

Here's the (low end) devices I own. One is an HoldPeak HP-90EPC, the other is an GBC KDM-110 I am following the book "Make: Electronics" by Charles Platt and I am at the very beginnings, where it ...
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2answers
63 views

Can a trim-pot wiper or contact point gets oxidized over time?

Can a trim-pot wiper or contact point gets oxidized over time? For example when a potential (high) current is flowing and the contact point of the wiper on the resistive element heats up a little. I ...
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2k views

Why does the cable resistance jump from a low value to high value at a particular frequency?

I am not well versed with transmission line theory so if you can redirect me to relevant material I'd be grateful. So I used Agilent 4294A to find resistance of a 2 metre long shielded twisted pair ...
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1answer
30 views

Velostat sensitivity to temperature

Velostat and some other type of conductive fabrics change resistivity based on pressure, but I did not found information about its sensitivity regarding the temperature. Is the velostat resistance ...
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3answers
126 views

What is initial contact resistance in relays?

I am reading datasheet of a relay. I see a term, initial contact resistance in relays. What is the definition of this parameter? Thanks.
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Best conductive ink mixture for potentiometers

Im 3d printing a model for a 2 axis potentiometer, and I need a carbon ink mixture that will hold up to the copper wiper, and produce around 10kOhm resistance in a line around 1mm*6mm. Searching ...
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1answer
89 views

Calculate resistance of an unknown resistor in a circuit

I am currently studying some old exams for the upcoming one and I got stuck on this question, I seem to get the right answer by eyeballing the circuit but I want to be able to calculate the value. ...
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2answers
90 views

In measuring relay contact resistance, should I use 4 wire measurement or calculate it using the voltage across the relay and current?

I'm reading mixed things online where a current from a typical ohmmeter is too low to accurately tell us the true resistance of the relay contacts. I've got a 30V 2.5A power supply, electronic load, ...
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2answers
89 views

Voltage spreading to resistors network

I want to model several electrodes (say 3) and GND on a resistive substrate. simulate this circuit – Schematic created using CircuitLab To characterise it, I apply a current on one electrode ...
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1answer
115 views

Using op-amps to read real-time resistance values over a wide range

Background I have been using a simple inverting op-amp circuit and Arduino to measure the resistance of a photoresistor (light 5k, dark 200M), like in the schematic below. This provides linear data ...
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1answer
96 views

Where did I miscalculate ohms law in my experiment?

I thought I finally had a grasp on how ohm's law works but when I set up an actual experiment, the numbers don't match up. To keep a long story short, I converted a computer power supply into a lab ...
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AC resistance of LVAC transmission line

I'm currently working on a project to determine the transmission losses in an LVAC line, as part of an off-grid distributed generation system. The manufacturer of the cable has given me a DC ...
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0answers
35 views

multiplexer resistance increasing is that means its dying? [closed]

I have a multiplexer 16 channels for arduino suddenly its stop working and when i measured this with multimeter each pin from mux produce 2k ohm, and when i measured this with arduino pin it measure ...
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1answer
65 views

How do I figure out the equivalent resistance of a network of resistors on a microcontroller?

I am trying to figure out what the equivalent resistance would be at a certain point in a resistor network given different conditions of the GPIO pins they are connected to. Configuration 1 is when ...
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2answers
505 views

Why does resistance reduce when a conductive fabric is stretched?

I just purchased some conductive fabric and noticed that stretching the fabric reduced its resistance. This seems counter-intuitive since stretching a wire leads to an increase in its resistance. I ...
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1answer
56 views

How to calculate equivalent resistance in mixed circuit?

I don't understand is this paralel or serie, can somebody help me?
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2answers
70 views

Resistance and wattage [closed]

I have a 6 Watt LED strip. When I turn it off it flickers briefly every 20 seconds or so. I placed a 20 Ohm, 1/4 Watt resistor in parallel across the connections to the LED strip and the flickering ...
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2answers
108 views

Why does a larger wire cross section mean less atom-electron collisions when there must be more atoms, too?

Regarding how resistance varies with diameter I've read this simple explanation on Quora: As electrons move across a wire, they constantly collide with atoms making up a wire. These collisions impede ...
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3answers
87 views

Voltage loss on DC circuits

I want to connect 4 bulbs in parallel. The bulbs need 12V DC and rated 18 watts. P=V*I, that means I=1.5 A on each bulb. From that the resistance of the bulbs are 8 Ohm (R=12/1.5). The circuit will ...
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1answer
41 views

Effective resistance of a NMOS

How do we calculate effective resistance of a NMOS, operating in linear region across drain and source?
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1answer
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What additional factors need to be considered when calculating voltage drop?

Considering the following formulas for voltage drop, what additional factors need to be included and how can resistance be derived to thoroughly calculate theoretical voltage drop for multiple ...
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Bad headphone driver resistance

I have a pair of ATH-M50 headphones where the right side has stopped working. I took them apart and measured the resistance at the L/R terminals on each driver. The good one measures about 35 ohms ...