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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58 views

Idea behind Thevenin equivalent circuit

As i know, we find a thevenin equivalent resistance by finding open-circuit voltage and short-circuit current and then divide these two. I have looked on wikipedia and other sources but could not find ...
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How do I measure the duration of transient from a transient analysis graph?

I've assembled the following circuit: And the following graph is the output: (Green: Voltage across C) (Red: Supply Voltage) How do I measure the transient duration from the graph? Is it the same as ...
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Generalized Power Equation, Ohm's Law and Ohm's Power Loss?

I'll try to state my questions precisely as I can. I'm a beginner in Electronics and since I have a background in Physical Chemistry and basic Calculus, the book Practical Electronis for Inventors, ...
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How to measure resistance without desoldering?

I am new to this forum, and have a question about a damaged drone flight controller. (Esc on aio fc) I have a problem with my fc. The problem is that a small component is gone; one of the components ...
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Finding Op-Amp Output Resistance using Datasheet

I'm using this TL071 op-amp datasheet and I am trying to find the op-amp output impedance on the datasheet so I can calculate the output impedance when used in amplifier/peak detector circuit. Do I ...
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Where does the input resistance formula of a BJT amplifier come from?

I just solved the (a) question of this problem from one of my past exams. And I am a bit confused on to why the solution is as follows: Rin = 100kΩ || Rib Rib = (rπ + (1 + β)Re) And the way Rib is ...
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How do I calculate load resistance?

I'm here with yet another problem. This time I can't figure out what the question wants. I've calculated the Thévenin equivalent, however I can't work out how I should calculate the RL. Is the load ...
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Finding the resistance of a resistor without multimeter

So this is a trivial but frustrating issue I’ve come across. I have two 5 band resistors and I am having a hard time differentiating the tolerance band. I don’t have a multimeter on me and I don’t ...
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Shunt resistor to measure voltage on the load resistance [closed]

I have to answer this question but I can't do it at all. Can somebody help me, please? The question is: "There is current control on the feature. Let the bus works on batteries with nominal voltage ...
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Why does current only choose path of least resistance sometimes

Say we have the following setup simulate this circuit – Schematic created using CircuitLab Input is pulled high and current flows through it as long as the switch is open. As soon as it closes ...
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1answer
32 views

How does BME280 measure air humidity?

I know that BME280 measures pressure using the piezoresistive effect, I suppose it uses the thermoresistive effect to measure the temperature. How about humidity? Any advice would be appreciated, even ...
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271 views

Why does AC input have a parallel resistor and capacitor?

Well, I am trying figure out a situation with images and a circuit diagram. I am checking all part looks normal, but if I insert this board on a machine the resistor is exploding and one leg of ...
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Heating Nichrome wire to 65°C

So I want to provide some heating to what will be like a fibreglass bucket and am contemplating adding some nichrome wire between a couple of the layers of fibreglass mat. I would ideally like to ...
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Getting thevenin equivalent when there's a current source only

I am stuck in finding the V-thevenin in this circuit. So what i did first is removed the current source and replaced it with an open circuit. After that i got the Resistance thevenin which is the ...
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why can i only know conductance and susceptance,not impedance from open-circuit test?

1.open-circuit test determine the electrical conductance and susceptance,not impedance 2.close-circuit test determine the impedance ,not electrical conductance and susceptance First,i want to ask ...
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How do I apply Thevenin theorem in this problem?

Can't find the answer to this question. Am I supposed to get the voltage in the 4 kilo ohm resistor? Really appreciate it if anyone can solve this one! Here's the circuit:
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Are the the 3 resistors in parallel or in series?

this might be the most stupid question on here...but are R1, R3, and R2 in series ? or R1 and R2 are parallel ? I'm fresh new into all this. Here's the circuit:
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Transmission line length with sag [migrated]

I have a straight-line distance of 250 Km between two towers and want to find the length of the transmission line that is between these two towers while accounting for the sag. The line should be ...
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Solid state switch with Terra-Ohm off-impedance

I am looking for a way to create an ultra-high impedance switch without mechanical components. The off-resistance should be around one Terra ohm for a signal range of 10V DC max. On the other hand, ...
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How can I get the total resistance in this question?

How do I get the total resistance here when there are two terminals A and B?
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108 views

How to calculate \$R_{\text{in}}\$ in this circuit?

I know for an ideal inverting op-amp, the equation for finding gain would be \$\frac{-R_1}{R_{\text{in}}}\$, but how can I find \$R_{\text{in}}\$ in this circuit?
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Is there an equation for the relationship between illuminance and the resistance of a light dependent resistor?

All I've seen on this is: R = A.Ea. where E – illumination (lux), R – resistance (ohms) and A, a – constants. The value of ‘a’ depends on the CdS used and on the manufacturing ...
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Gamecube controller hack with raspberry pi

Electrical noob here. I am trying to control a gamecube controller from a raspberry pi. Meaning: I want to have wires from the pi soldered onto the board of the gamecube contoller and emulate button ...
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iphone 6 plus - Is the resistor R0601 important?

What is the resistor R0601 important for? Can a iphone 6 plus work without it ? What is the meaning of the code (ZQ) in the iphone schematic? Thanks
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How do I calculate resistance when I have the voltage drop?

This is my circuit: 3 volts in with a 1k ohm resistor in series with the LDR. I have the voltage drop across the LDR but I need to find the resistance.
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Why is the resistance on my PCB low?

I am designing a PCB for a LED, photodetector (several different tried), TIA (OPA380), and linear regulator (LT3042 to reduce noise). It's on FR4 from OSHPark. When the LED is on the photodetector's ...
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Why can't i calculate the Inductive reactance in this way?

Question: \$V_1=40sin(1000t)\$,what is the value of Inductive reactance? Solution : \$Z=\frac{V_1}{I}=\frac{40}{8}=5\$,so \$5=\sqrt{R^2+X^2_L}=\sqrt{4^2+X^2_L}\$,so \$X_L=3\$ But i want to ask ...
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Output resistance of CE amplifier small signal model

I was studying input/output impedance of CE amplifier small signal model and I wanted to know why the output impedance (looking from the collector) is just Rc in parallel with dynamic output ...
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Equivalent resistance of unbalanced Wheatstone bridge and generalization

I was wondering what could be the simplest method to find out the equivalent or effective resistance of an unbalanced Wheatstone bridge (first figure) and if this method can be generalized further (...
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DVOM nonstop auto ranging resistance on 1 pin of potentiometer

I think this is a newbie question, but I was trying to measure a couple of pots with my new meter, and on one set of measurements (one set of pins) I'm just getting a nonstop auto ranging all over the ...
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62 views

DIY Spot welder power- limiting factor?

I'm trying to build a spot welder for spot welding 18650 battery packs but I can't get it to work (very weak welds). The goal is to be able to weld 0.3mm thickness steel strip (nickel plated steel ...
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31 views

Measuring conductance of the material used in fabricating Antenna

I have a composite polymer material with injected conductive particles inside it, making it a not-so-perfect conductor. I have also fabricated a simple dipole antenna using the wires made of the ...
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60 views

why is \$P^{max}_{R3}=\frac{V^2_{th}}{4R_{th}}\$,not \$P^{max}_{R3}=\frac{V^2_{th}}{R_{th}}\$,why should we have to multiply \$R_{th}\$ with \$4\$?

The question ask me the power that R3 consume,here is the schematic and my calculation simulate this circuit – Schematic created using CircuitLab My calculation: I modify the left part of the ...
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71 views

What is the Ohm measure value of this resistor?

Resistor Ohms Value? In diode mode test, it will show continuity or sound. is fused or blown. It is in the negative line of Electrolytic 400volts 22uf capacitor, such capacitor in direct after the ...
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Redrawing a wye circuit

Instead of using wye delta transformation I tried redrawing the following circuit but I do not understand where I made a mistake. The circuit appears to have the same voltage current relationships at ...
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188 views

Measuring very small changes in a low resistance circuit

I have a circuit where I am trying to detect when a systems resistance drops from ~5-20 mOhms to half or lower (~<1-10 mOhms) with a micro controller. my microcontroller can read between 0-3.3v ...
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57 views

What is the maximum resistance that is allowed when connecting two grounds in a 5V unit?

Say I have a 5V Arduino and I want to connect two grounds (I don't have another idea of anything else I would like to short). How good should the conductive between them be? For example if I want to ...
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47 views

Why does an oven plug burn out when all knobs are on full-setting?

I'm having serious trouble understanding this. If a component burns out when too much current is flowing through it, then how does turning on all stove-tops to their full setting burn out the oven's ...
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89 views

MOSFET small signal model output resistance

I am wondering what is the output resistance of the circuit below. I found that it depends on the gate voltage: $$ \begin{aligned} R_{out} &= \frac{V_{out}}{I_{out}} \end{aligned} $$ $$ \begin{...
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Rogue resistance between Vout and GND in LDO circuit

I'm currently developing a circuit as seen here:. I had some suggestions to check my Iout to ensure that I wasn't drawing so much current that I was causing an overheat. After a little checking I ...
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1answer
51 views

UWB circular antenna: input impedance (Zo= 50 Ω)

I'm having difficulty with the line input impedance of the circular planar antenna signal. Its impedance is 117 ohms and the correct is 50 ohms, I am not able to lower the value. I made modifications ...
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2answers
109 views

What value resistor to add, so my motor provides the correct amount of power?

Motor Specs & Circuit Diagram I'm an Aero student with virtually no electronics knowledge. I'm trying to figure out what value resistor to add to this circuit, so my motor provides the correct ...
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Measured Q factor of LC circuit does not correspond with calculated and simulated

Still having a problem with measured value of Q factor of parallel LC circuit. My measurememt setup looks like on the picture below. I use Function generator SFG-1003 and Oscilloscope Rohde-Schwarz ...
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3answers
155 views

How to calculate Resistor needed in PNP Transistor Circuit

I am trying to calculate the resistor value I need to achieve 35mA in my circuit. Vcc is 5V. Can someone explain the values I need to find in the datasheet as well as formula to use to find the ...
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We can ignore the wire resistance if the current delivered by the wire is low?

In this question asking about the Resistance of wire, the answer by user 比尔盖子 provided the following explanation for When Resistance Can be Ignored: Most of the time, resistance of a wire is too ...
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For the network shown in the figure, draw the corresponding Thévenin equivalent circuit and establish its parameters VT and RT

I can't find any examples online similar to this format, please help! Attempt: RT = (2*5)/(2+5) = 10/7 = 1.429 k-ohms VT = 8V + 8V = 16 V Do you ignore the center resistor and just add the voltages ...
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Will the resistance of the certain valued resistor decrease or increase at cryogenic temperature?

I tried to measure resistance of 332k Ω while dipping in liquid Nitrogen (cryogenic temperature) I got the resistance value near about 458k Ω, doesn't it contradicting "Resistance should increase and ...
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2answers
54 views

Finding small signal resistance for MOSFET

I need to find the small signal parameter \$r_{D1}\$. I understand I must draw the small signal equivalent first, but I do not know where to label this resistance, or what exactly it is equal to. Also ...
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Equations for a simplified transistor circuit

In the following circuit: I would like to greatly, greatly simplify how the components work just to be able to make a dumbed-down version of the equations. Let's assume the forward-voltage of the LED ...
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Fundamental Questions about Voltage and Resistance

I hope all is well. In this post, I’ve asked a couple of very fundamental questions regarding the topic of electrical engineering that my current education vaguely answered—and unsatisfactorily so ...

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