# 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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182 views

### How does one know that the current is flowing downwards through the $8 \ \Omega$ resistor?

I'm currently studying the textbook Fundamentals of Electric Circuits, 7th edition, by Charles Alexander and Matthew Sadiku. Chapter 1.7 Problem Solving gives the following example: Example 1.10 ...
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### What is the difference between LDA 210 and LDA 212?

Do you see any difference between LDA210 and LDA212? Can it be that a factory produces the same product with different names? LDA210 datasheet: link LDA212 datasheet: link Official comparison ...
22 views

### Calculating the change in output voltage as temperature changes the control feedback resistance

I am trying to calculate the new output voltage when the temperature changes the resistance of the feedback network which sets the output voltage. I have this circuit using the MCP16311/2 buck ...
93 views

### How can I solve this opamp circuit?

I am designing an Analog Front-End circuit for an NTC Sensor which has 3 parts, the non inverting stage, the low pass filter, and goes to seeeduino. Basically the input voltage is 5Vcc and I need to ...
91 views

### Voltage issue on pull-up resistor

I have an I2C sensor circuit, 3.3V applied to SDA and SCL pin through 10k resistor. I2C communication is not working so I have measured the voltage drop across the 10k resistors. It drops 2.86V and ...
42 views

### SMPS power supply - fuse resistor calculation

I'm designing a TNY288-based SMPS. My transformer input inductance is 931μH. I'm using a 320V MOV and have a doubt about the fusible resistor calculation. The output load is 12W, the input capacitor ...
75 views

### What size does my resistor have to be for the IC input?

I am testing some logic gate ICs to include in future projects. However, even when both of my switches are off, my logic IC is still sending a logical HIGH to my LED. I think my problem is the same as ...
15 views

### Source Transformation Finding TEC

I have been trying to find the thevenin equivalent circuit with respect to nodes a and b using source transformation. I end up having this setup. What would possibly be the next step I should do? Can ...
52 views

### Resistor identification of crock pot

I'm having a problem with my crock-pot: the device turns on, but when selecting anything, it just turns off. Opened it up, and found the pictures below. I think resistor R49 is the problem - but since ...
37 views

### Are 4N35 optocoupler clamped at 22V?

I am trying to detect mains with an ESP32, for that I started testing this circuit: I bought a 4N35 optocoupler and 110kΩ resistors. My first test was using 2 resistors in serie, so R1 = 220kΩ The ...
53 views

### What is the difference between making a resistor based keypad and not using a resistor on arduino? [closed]

I've seen videos on youtube about how to emulate a keypad on arduino. Some of them includes a resistor while others do not. What are the difference between them and are there advantages in doing one ...
55 views

### My light-dependent resistor gives a fluctuating serial output

I'm a high school student trying to make a light tracking single axis solar panel. I am using an Arduino Uno rev3 board. When I first finished building it, the system failed to operate. I spent a few ...
573 views

I have 9 thermistors arranged in a grid, and I want to average the readings from these thermistors without code (that is, average them in a circuit rather than reading all the values into a ...
840 views

### Why does this resistor not exist?

I have a 5W 5-banded resistor that shouldn't exist according to the color code chart and I've never come across this before. The color bands are brown, green, silver, gold, black. Now looking at it in ...
70 views

### E Series: is there any place that explains it?

So I am doing a work on optimizing circuits, and I came to study the E series of components. I'm a bit confused and I cannot understand soem things: How do the tables of values (E3: 1.0, 2.2, 4.7) ...
78 views

### Parallel RC circuit differential equation for a mechanical engineer

For a mechanical engineering course in controls, I was asked to Write the differential equation, state equation, and transfer function for this circuit That's the full text of the problem, and the ...
163 views

### Resistor in my AC LED circuit gets fried

I have designed a dead simple LED circuit I calculated the required resistance to be (220-2)/0.02 = ~11k so I used 10k+1k resistors in series but for some reason, ...
51 views

### Reducing 12v to 5v with convertor

To start, I'm a complete layman on this topic. If I say something that sounds inaccurate please do correct me. I'm here to learn as much as I'm here to ask for help. I have a truck with aftermarket ...
96 views

### Can I reduce AC current to vent from from 3A to 2A?

I have a range/stove hood with a really strong and loud blower motor. It's so strong that when we moved into our small house, the inspector made me disable the highest 3 speeds/CFM fan levels (600CFM) ...
103 views

### Replace LED with resistor in Christmas light string

A rodent chewed up an LED socket on a 100 light, warm white 3.2 V light string. I want to replace the socket with a resistor to keep the string within its voltage and current parameters. What would be ...
69 views

### Looking for help identifying a resistor value

A resistor has burnt out in my heat sealer. Can anyone help confirm the type? From what I can find online it seems to be a 89G Ohm - is this correct? The body is 17 mm long.
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### Getting current and voltage on a resistor using simplification

I hope it's okay if I ask it here, but I've been playing with this current for quite some time now, and I've reached a dead end. I am supposed to find the amperage and voltage of a specific resistor (<...
202 views

### Resistive divider as resistors approach 0 ohms

Resistive divider when R1 = R2, split voltage in half because V = IR, and resistors in series add as Rtot = R1 + R2. It seems like this must break down as R1/2 approach 0 ohms. Anyone have a good ...
81 views

### How does a pull up resistor change a voltage divider calculation?

I am using this proximity sensor with a raspberry pi. the sensor outputs a 24V signal when triggered, which I need to step down to 3.3V using a voltage divider so as to not blow out the pi. The ...
985 views

### What are these components used for in the Arduino Nano?

What are the functions of the component(s) in the: red blue green circle? And what is a "+5V auto selector"? https://store.arduino.cc/products/arduino-nano
61 views

### Resistors max AC voltage datasheet

I want to make this circuit: Where Sens2 is mains (233VAC in Switzerland) I found this resistor that look perfect for the job: RND 155SP12 3W (datasheet). I don't understand what does max voltage ...
69 views

### What type of resistor is needed for 5V 2A power? [duplicate]

I am new to electrical engineering. I need to power a control board that requires a 5V power supply. The instructions specify "5V 2A or 4A". I have a USB port that specifies a "max of ...
82 views

### Easiest way to make a resistor [closed]

What do I need to make a resistor of about 10 kΩ? After I make it, how do I measure the resistance with this device:
220 views

### I'm new to circuit analysis and completely stumped on this circuit. Could someone please help me understand the steps to solve it? [closed]

I have to calculate the current and equivalent resistance but I don't even understand where to start. I'm not looking for a straight out answer I just want to know how I should go about solving it?
112 views

### Resistor between 74595 SRCLR and GND

What is the function of this resistor and is it okay with this value ? Rizki
2k views

### Why do resistors "draw" current? [closed]

I was looking at an explanation for why parallel resistors have less resistance: Resistors in Parallel One of the answers involved simulating parallel resistors as a black box and it made sense. If ...
24 views

### Converting Delta-Wye to Wye

To convert the delta part of this circuit to wye, is it correct to do (6-8i)/3 and then to combine the two wyes, as they are in parallel, do (6-8i)/3 // (4+3i). Then will this form one wye which is 2....
31 views

### Calculating capacitor voltage with initial conditions in an RC circuit

If the initial voltage of the capacitor at 0s is 20V, would the equation for the voltage of the capacitor at a specific time be; 60 + (20-60)e^(-t/RC) or would it be 80 - 60e^(-t/RC)
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### Identifying Parallel Resistors from Series

I have this circuit that I am analyzing, but I am a bit confused about how the resistors are connected here. One end of the 200 ohm resistor is connected to the 50 ohm resistor while the other end ...
94 views

### Buttons in parallel - short circuit? [closed]

I encountered a problem while trying to use 21 buttons at the same time. Initially, I did not take into consideration that they could be pressed all at once. And while measuring the resistance I ...
95 views

### Transistor resistor calculation help (design revision 1)

I posted my original design yesterday and got many comments about my errors. This is revision 1 of my design. I am now pretty sure I have the load resistors calculated correctly, but still unsure ...
92 views

### Why is my piezo buzzer emitting a clicking sound?

I'm trying to make a voltage controlled oscillator (VCO.) It works just fine, but my piezo buzzer keeps clicking in conjunction with the square wave the NE555P is producing, making a weird effect. Is ...
94 views

### Transistor Resistor Calculation

I am new to electronics so I'm not too sure about how I should be calculating the base resistor to use in this circuit. I think the load resistor is calculated correctly (data sheet at bottom for ...
63 views

### Resistor in series with Vcc [closed]

Suppose I have an IC where I connect a series resistor with Vcc and '+Vcc' supply pin of IC. Refer to the schematic above. Say the IC current consumption is in uA or few mA for a supply voltage of 3V, ...
50 views

### Protect high voltage little currents

Short question: Are there alternatives to very low currents fuses? I need something that breaks at about 6 mA. and I cannot find anything like that. Long question: I am trying to detect mains (230VAC) ...
148 views

### Why do two different approaches give different results about choosing resistances for voltage divider of emitter follower circuit?

I have read this page from the Practical Electronics for Inventors book. What I don't understand is about the calculation of R1 and R2. Approach 1: This approach is author's idea and the result is R1 =...
67 views

### Replacing 1k resistor [closed]

I just bought new soldering station, when I turn it on the solder some thing burned inside the soldering station. When I open the soldering station I found out that 1k resistor burned out. Do I ...
64 views

### How to solve this resistance calculation question:

I need help to solve this question, the first part was to solve for the missing currents which I have done, and the second part is to calculate each resistor value. On the left is the circuit given on ...
48 views

### Question regarding equivalent resistance

I am looking at an example in my text regarding Thevenin circuits and when they set the voltage source on the most left hand side to zero and solve for the equivalent resistance they get the following:...
72 views

### Sine wave signal lagging; potentiometer has inductance? [closed]

my sine wave at the midpoint of potentiometer is lagging by 74 degree when comparing to the input, and my potentiometer is 500Kohm. Is there a low inductance potentiometer? I do not know how to pick a ...
794 views

### Time constant of this circuit

Can someone tell me on why the time constant of the below circuit is not R2*C? simulate this circuit – Schematic created using CircuitLab My understanding is that, the Capacitor C1 is getting ...
47 views

### On what factors does the I2C pull up resistor values depend upon

I was reading this Article regarding the pull up resistor calculation. I understood that the value of the pull up resistors depend upon the currents, the supply voltage and the Logic Level voltages ...
66 views

### Variable resistance controlled by micro controller

I wish to remove 2 resistors in power supply unit and put variable resistors that would be controlled by my microcontroller. 1st resistor should be in range of 3000-6000 Ohm 2nd resistor should be in ...