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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Doubt regarding Combination of Cells

I was unsure of what the voltmeter would read: the terminal voltage of the top cell, or the voltage across the parallel combination of cells. I tried calculating both ways, but both give the same ...
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24 views

series termination resistors for SPI communication

I am designing a PCB where I have the PIC18F26J50 interfaced to the MRF89XAM9A through SPI. This would be an on-board communication. Do I need to add series termination resistors to match trace ...
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2answers
67 views

Replacing resistors with active load in active filter

I am building a low pass filter IC in 0.25 micron CMOS. My design requires 14 Mega-Ohm resistors. I want to replace them with an active load in order to save space. If possible I would like to use a ...
2
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2answers
97 views

Equivalent Resistance? [duplicate]

How do you find the equivalent resistance here? I tried using Kirchhoff's laws, but there is no cell given.
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3answers
101 views

How does adding two Resistors in Series contribute to the sum of its resistances

I would like to know why by adding two resistors in series we would get a sum of it's resistances.I know by Ohm's Law that since $$R=\frac {V}{I}$$ it's certain that you would attain the equation ...
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1answer
55 views

Why does USB signaling to microcontrollers need resistors

I'm currently trying to make a USB device with the ATMega16U2. On page 187 of the datasheet, there are unspecified resistors between the USB port and the pins of the microcontroller The Arduino Uno ...
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5answers
101 views

What is the role of resistor in this schematic?

I am a beginner in Electronics and I am not able to understand why do we need to put this resistor(Resistor which comes after the switch) in this schematic? Does it save IC from current? but how ? ...
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3answers
20 views

Current always goes to less resistance?

I read in a book that "Current always goes in the less resistance path". In a paralel circuit with 1k resistor to one side and 10k resistor to another side the current still goes in both sides. Why ...
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4answers
295 views

How can a resistor affect current AND potential at the same time?

Though the resistor is always introduced as one of the most simple components it is the one which makes least sense to me. Ohm's law defines the resistance as$$R = \frac{V}{I}$$ this means that the ...
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2answers
82 views

Calculating resistance of series/parallel circuit

If I have a configuration of 5 resistors as follows: simulate this circuit – Schematic created using CircuitLab How can I calculate the expected total resistance between A and B, given ...
2
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2answers
544 views

What's the difference of placing multiple resistors and one resistor for limiting the current of LEDs?

I'm looking at a diagram and wondering if I could use just one resistor to limit the current of the LEDs instead of multiple resistors so that the cathodes are all connected to the same resistor. ...
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1answer
61 views

Creating a raising edge to wake up the micro controller

Need help in understanding the following circuit. The documentation says the STM32 micro controller can be woken up by a raising edge. My interpretation is that the pull up resistor connected ...
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3answers
92 views

Custom Resistor

I need to build a resistor that will serve as a heat source to test the performance of a Peltier cell. I want the resistor to have a square plate geometry, of 40 mm × 40 mm and a height the shorter ...
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58 views

Find the output resistance?

I tried a lot to solve the value of Rout but failed.What is the value of Rout? This is what I did(shown below)
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1answer
77 views

Choice of heating element (power resistor)

Basically I need heating element which can heat up small volume of air (lets say shoes box size) up to about 60 C degrees. I am going to use 25 V source supply with 2 A current. What I thought about ...
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4answers
294 views

what could be the visualization equivalent of the resistors in series?

Why do resistors in series add-up? Is there any visualization equivalent of that? I have in mind electrons as cars driving on the highway, now a resistor could be a narrow spot (R1) where cars are ...
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2answers
38 views

Do I need a current limiting resistor for MAX383 digital logic?

I'm trying to control a MAX383 analog switch using a Raspberry Pi, through an optocoupler (Sharp PC817), to separate digital logic from the analog section. On the analog side, I will have a bipolar ...
0
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2answers
58 views

12 VDC LED strips get too hot [duplicate]

Package reads "2 8in 12vdc LED strips". Plugged into a car they get hot enough to melt. Plugged into a 12vdc 120mA transformer they work great. What resistor do I need to bring car amperage down to ...
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2answers
91 views

Purposely draining a battery by a resistor

I'm new to electronics and wiring, and wonder if a 15 ohm resistor will drain a 1.5v battery (specifically a Duracell Alkaline AA) in a reasonable amount of time to a super-intense white LED. Does ...
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2answers
104 views

Calculating resistor's value to use it with a LED

There's something about the LED formula that I don't understand. It says that if I have one LED with a forward voltage of 3V and a forward current of 20mA then if I want to drive my circuit with a 6V ...
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4answers
1k views

why is the time constant(RC) measured in seconds?

This is to fulfill my own curiosity as I haven't had much luck at finding the answer. I would be most grateful if someone could give me a solid answer or send me in the right direction. Thanks
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1answer
571 views

Why is this resistor connected between connector shield and ground?

I was looking over my raspberry pi model B and I noticed a resistor between the USB power connector shield and ground. I've noticed this on many PCB designs with much larger packaged resistors ...
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1answer
86 views

Resistor set up to drop to 12V for LEDs

I generally work with 12V standard and simple DC wiring. Awhile back I put a bunch of LED lights on a bicycle for a Youtube video, though I ran them off of a single 9V battery. I would like to run two ...
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3answers
341 views

Total resistance with resistors bridging two branches

I know how to calculate resistance in parallel and series connected resistors, and how to reduce most circuits to these, but I missed my lecture on cases where you can't just reduce the circuit to ...
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1answer
42 views

Inverting effect of resistance in an RC circuit

I have a question on basic electronics. I'm looking at a very simple CMOS RC Circuit around a Schmitt Inverter which creates square waves. Something like this. simulate this circuit – ...
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2answers
286 views

Another 'What is this component?' question

I have looked through all the other 'what is this component' questions and have not found my component. I am looking for the component in the red box. It is from a rectifier circuit off a 1973 9.8 hp ...
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2answers
100 views

LEDs, Voltage and Resistors

I noticed that a Christmas Light uses 20 LEDs in series parallel, operated by 2 AA batteries (3V) without a resistor. I thought you always need a resistor? Would it be possible to run them on 5V ...
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1answer
100 views

Can I overload resistors when they are in parallel?

I have 10 x 100 ohm, 1/4 watt resistors in parallel, to get a total resistance of 10 Ohms. I do not have a datasheet for these, so I cannot look up the maximum ratings or anything like that, so I ...
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4answers
111 views

How do current limiting resistors work between ICs?

In a simple battery+resistor circuit with a fixed voltage, the resistance of a series resistor determines the current flowing through it. But what happens if this resistor is placed between two ICs? ...
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1answer
125 views

Using a transistor as a heater

I have the task to build and control 35 heaters, 10 W each. I first thought about using power resistors (like in this datasheet) as heating devices, but they'd need high currents in order to get the ...
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1answer
298 views

Placement/Location of pull up / pull down resistor?

I have connected a microcontroller GPIO pin, which is intended to be an output, to a DC-DC converter's active high Enable input pin. Since this pin is active high, and because I do not want this ...
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2answers
85 views

Voltage Division Problem

Hello good EE samaritans, I currently taking MIT 6.002 course to get head start prior to starting EE next Fall. Right now, I am really struggling with this first lab. Problem: You have a 6-volt ...
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5answers
100 views

Circuit Simplification

Calculate the current shown by the ammeter. simulate this circuit – Schematic created using CircuitLab How do we solve this using delta-wye transformations?
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1answer
76 views

Connect 8 ohm speaker output to microphone input on another system

I see the question was answered in 2013, but in addition, Id like to ask the follow question(s); I have a significantly stronger speaker (output) than a computer speaker discussed in previous post. ...
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1answer
92 views

Can this be anything other than a resistor?

I have been messing with an old valve amp and have replaced the filter caps and a couple of resistors that were a little out of tolerance. The component in the picture does not look the same as any of ...
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3answers
104 views

What are the mechanisms at work in a pull-up or pull-down resistor circuits with a push-buttons and a GPIO?

I have a question regarding the GPIO (from a Arduino board for example). How does it work exactly when you use it as an input pin? What are the mechanisms at work when you use it in a pull-up and ...
2
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4answers
241 views

Find the resistor's value

I have bought some resistors and I am trying to find their value. The thing is that in class they taught us that you use the gold strip to find which is the right side at first and then you check the ...
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1answer
67 views

How to solve this circuit using mesh analysis? [closed]

simulate this circuit – Schematic created using CircuitLab How would I solve ...
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3answers
147 views

May I power atmega32a-pu microcontroller from AA batteries?

I need to provide +-4.5V to the microcontroller. That would be fine by having 4x rechargable batteries, but how is it with current? On each AA battery is written min.2550mAh. I am not sure but I think ...
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3answers
446 views

What does a resistor do?

Ok, very basic question here. I read lots of books, searched quite a bit, and every description I read seemed to talk about the flow of electrons and go too right away deep in theory for me to grasp ...
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3answers
1k views

LED strips: 46% resistive losses?

I recently bought these LED strips. They are supposed to run on 12V/72W and have 300 x the SMD 5050 LEDs on it. Schematic: simulate this circuit – Schematic created using CircuitLab The ...
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0answers
35 views

PNP collector voltage drop under fan load?

Im trying to build a circuit to drive a fan. Im following an example that i found online. R5 is a 10k thermistor R6 represents the fan to drive (starting resistance 70k). Its a 12v pc fan but it will ...
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3answers
138 views

What is the drawback of a high-value resistor for positive comparator feedback / hysteresis?

I'm building a simple circuit which has an LM211 comparator at its heart. The positive input is connected to a 10k-10k resistor divider across the supplies, stabilized by a 1uF capacitor. Hysteresis ...
0
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2answers
102 views

What is the need for a pull-down resistor in this schematic?

here at the second page: http://www.skyeinstruments.info/index_htm_files/W200P%20Windvane.pdf there is an external 470k resistor in parallel with the measuring device. it seems like the manufacturer ...
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1answer
69 views

Inductor held with hands

I have a fairly simple problem, but as I am a newbie in electrical circuits I was hoping someone might help me understand the principles of things. I have a circuit with an inductor of L = 0,102H a ...
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1answer
72 views

Why isn't this LM2917 circuit working to turn off a transistor?

It was suggested to me that I should post a new question (original question here: Minimal Hall effect sensor circuit to keep something off after certain RPM achieved). The below schematic is for ...
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2answers
87 views

What should be the value for the resistor for this circuit?

Sorry for this silly question but I am not from an electronics background. I am trying to build a very basic circuit with npn transistor to detect a certain water level. I am assuming the resistance ...
0
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2answers
84 views

How to find the expression for Vout?

I have that circuit and I need the equation of Vo, I've been told that I can solve it by the Kirchhoff method but I'm not sure. Is there a way that the expression looks like Vo=K(V2-V1) ?
2
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6answers
165 views

Is there a non recursive formula for mixed resistors?

In equivalent resistors in multiple parallel resistors, like this simulate this circuit – Schematic created using CircuitLab I need a formula for the equivalent resistance for the ...
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2answers
114 views

Calculate mosfet gate resistor?

I got this schematic : In the image you see; I'm driving two infrared leds at 40 Ma each one with a FDN327N Mosfet. Attached at D8 there is one of Teensy 3.1 digital output that has HIGH voltage ...