# Questions tagged [resistors]

A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently $I=\frac{V}{R}$)

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### LED downlight current (amp) usage

I need advice on how to build a battery powered light setup in my house with what I have. Please be kind as I am a DIY newbie when it comes to off-the-grid solutions. Equipment: 1 x 12volt 36Amp ...
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### I need help finding the power

I need help finding the power of the 1 ohm resistor in this circuit. Could you guys give any tips or even some clues to find it ? I've been trying for a while with Kirchhoff's circuit laws but ...
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### How do we find where the average voltage resistor load formula came from?

Applying the half wave rectifier. We have in series a source called $V_{in}$, a diode and the resistor load. To find the average resistor load we use this formula : $(V_{max} - 0.7) / \pi$ I ...
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### What resistor type is best for use as a heater?

I'm working on a design that requires I heat a bank of 18650 batteries during their operation. The plan is to mount the batteries along with large axial 2W resistors in to a PCB and using small ...
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### Equivalent circuits in case of equipotential nodes

I have the following basic questions about circuit theory. 1) Consider a generic circuit. Suppose that, because of symmetry or other reasons, we conclude that two nodes A and B of it have the same ...
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### How to get NTC resistor's temperature vs resistor curve?

I have a thermistor MF52203 whose rated resistance is 20k. However, the datasheet seems like not providing the temperature vs resistor curve. Without this curve, how can I get the corresponding ...
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### How to calculate voltage of these nodes

How exactly does one calculate the voltage of the marked nodes and arrive at the numbers in the picture (1.75 and 1.628)? I fail when trying. :( simulate this circuit – Schematic created using ...
11k views

### Basic diode question about voltage-drop

We have been begun studying diodes in electronics 1 and I have really basic question that may be really dumb but I cannot find an answer online. If a diode is in series with a resistor and a voltage ...
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### 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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### Finding value of resistor between two diodes

I'm using an Arduino and I have the following circuit: I couldn't find the symbol for analog signal, so the voltmeter represents a connection to the Arduino's analog input pin. How can I work out ...
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### Small glass component with three colored stripes:yellow,green,and orange.The center of the component is a small cylinder

Small glass component with a tiny cylindrical structure inside the glass packaging.The colored stripes cover it up.
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### Thermal Noise autocorrelation and time domain analysis

I have some doubts about the termal noise of a real resistor. The equivalent model of a noisy resistor is this one (here the reference): Here there is the model of a noisy resistive network: I ...
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### Alternative to cartridge heater for 10mm deep hole?

I am designing my own version of a heater block for a 3D printer hot end. I had originally intended to use a 40W cartridge heater but the shortest length available I can find is 20mm and the geometry ...
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### 0603 LED resistor values

I have two LEDs The first one is directly attached to 3V3 and the other one is attacked to the SCK line on AT Mega 328P Here's the datasheet for the led (I am using the same LED) http://www.image....
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### Identifying Value of Burnt 5-Band Resistor [duplicate]

I've been having trouble identifying the value of this resistor (see picture below) as the color codes in position does not make sense. It looks like a 5 band coded resistor. The 3rd band seems to be ...
1k views

### Why do I need 2 resistors to divide voltage?

I know someone else asked the same question, but I wasn't able to understand it. My question is, why do you need 2 resistors (1 to ground), to divide the voltage? Just 1 resistor would do the same ...
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I have a single 3.0 ohm sub-woofer and a 500W RMS amplifier. The speaker is designed to run as a pair or 1.5 ohm however I do not have the space. Is there any inexpensive solution?
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### Convention to label components in a circuit

Given an un-labeled schematic like the below, is there a convention on how to label the various components? For example, would the 'top-left' resistor be R1? Would the one to the right of it be R2, ...
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### Lowering resistance of potentiometer?

I saw a video where a person wired a resistor to the outer pins of a potentiometer to lower the resistance. Does this work? And if it does, can I still use the wiper and an outer pin with it lowered? ...
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### solving circuit using mesh equations

Im trying to solve this circuit.I think ive got something wrong because the results are a little different than what i was expecting.Any help would be very much apreciated.Ive got this so far. -20 + ...
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### Why do series resistors have a single current running through them?

In a circuit such as the following: The current is the same through all the resistors and is: ...
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### How to model a load as combination of RLC (resistance, inductance capacitance?)

I have a constant voltage DC power source and a load connected accross it. The load consists of various sensors, modems, some small actuators, and something else which I don't know (mostly resistive.)...
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### Can a USB power source run 4 IR LEDs in series without a resistor?

USB is 5V, and the voltage drop across the 5mm IR LEDs I'm gonna use is around 1.2V, if I connect 4 IR LEDs in series and perhaps more in parallel, do I still need a series resistor? Will cooling ...
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### Resistor without terminals?

I have two terminals which I will measure resistivity between. I will be manually touching the terminal pair to different value resistors. The terminal pair might look something like a 9v battery ...
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### Simple Transistor Resistor Amplifier Circuit Question

Can Someone Please Help Me On Solving this. I have tried and stuck..In a point that can I apply Kirchhoff's Voltage Law around R2,R4 loop. simulate this circuit – Schematic created using ...
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### How to solve a LED-resistor parallel with a resistor?

Hi there I am curious as to how you would solve this circuit to know voltage drops and currents. It came about from a previous question I had asked which showed my understanding was not quite what I ...
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### Confirmation on Diode in parallel with a Resistor

In a circuit with a resistor parallel to a diode/resistor, will the voltage across both resistors be the supply minus the 2v drop of the LED? Meaning you would calculate it still by using resistors ...
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### What does the arrow going through the battery symbol represent?

I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5 Resistance, Resistivity, and Conductivity presents the following image (without description)...
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### Controlled Temperature Coefficient of chip resistor

I am designing and experimenting with current source circuit using Op amp and transistor. As output current increases, the temperature rises which then makes the output current value to change for ...
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### Resistor causing problems when in series with LED

I am wanting to dim the light on my computers power light, its just a 5mm LED what i am guessing gets 5v from the motherboard to power it The problem I am having is that when adding a 100R resistor ...
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### Current going into the positive pole of a battery while discharging a capacitor

Please bear with me if this is a fundamental question. Let's suppose we have an RC circuit, charging a capacitor up to the voltage of a battery of 9V. The capacitor is currently at 9V, we switch the ...
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### How to determine if installed braking resistor is correctly sized

I have a braking resistor attached to a system with a large rotational inertia. Everything works fine in terms of startup, rundown and normal operation. I would, however, like to investigate whether I ...
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### Diffrence between cr0603 and r0603

I am shopping for parts on mouser and was wondering if someone knew the difference between cr0603 and r0603 concerning smd resistors. You see this one has code CR0603 https://www.mouser.ca/...
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### Help regarding Ac current limiting using resistor

I've 12v(Vrms) 1A AC transformer. I need to regulate it to 1to 4ma maximum output without having much voltage drop. Output load is an animal skin which has resistance in it. Can I just use a ...
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### Why is voltage drop independent of this 4 Ohm resistor?

I have this resistor which is connected to some battery (not very important). I don't understand why the total voltage is equal to the voltage drop over the 3 $\Omega$ and 2 $\Omega$ ...
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### What is the total resistance in this circuit?

simulate this circuit – Schematic created using CircuitLab The parallel bit is easy enough but that 150k ohm keeps bending me over. If you could tell me how you got the answer it would help my ...
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### JFET circuit solving

I want to find out the value of R2, R3, R4, R5. How can I solve it? anyone can help me? For JFET1 VGS=0v, VDS = 15v. For JFET2 VGS=1v, VDS = 18v.
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### Why does LED dim when adding second LED in parallel with a single resistor

If I have a led hooked up to a 12v DC supply with a single resistor it runs nicely as you would expect. If I add a second LED in parallel the brightness drops, slightly, the brightness on both is (to ...
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### Figure out the Resistance Value With Known Device Specs

I'm learning electronics and trying to find the right resistor value for my device: a Eachine Rotg01 Receiver. The specs ...
114 views

### LEDs in series without resistor

Say I have an ideal situation (good quality functioning power source and components) - 12V source and 3V (each) LEDs. Can I wire these 5 LEDs in series to the 12V source without a series resistor and ...
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### Position of the voltage source with parallel resistors

In the following circuit I want to calculate the current flowing through the voltage source (node A) simulate this circuit – Schematic created using CircuitLab If I use the KCL I get \\$I_A = ...
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### Power resistor dealing with quick high current surge

I am currently working on a circuit to deal with the high inrush current of high value capacitors. I'm calling this a 'capacitor adder' as the rest of the circuit (output load) is already powered ...
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### Why does a circuit with only reactive components have infinite Q factor?

So I came across the statement in my textbook. So I have been trying to understand why this is the case, however I just have not been able to understand
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### Fairy lights dimming over time

I have had this cheap set of fairy lights for a few years. Powered by 3xAA batteries. Recently when they are turned on they start bright as they always were then proceed to get dimmer and dimmer ...