It's a measure of how much an 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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Simple Ohm's Law Question

Do I need a resistor if \$\frac{V}{I}=0\$? I am working on a simple circuit of an LED and a buzzer in series where the voltage drop would be 2 and 3 volts, so \$R=\frac{V}{I}=\frac{(5 - (3 + ...
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1answer
70 views

Resistance to use for a LED circuit

I have extracted a strip of 6 LEDs from a LED strip that has these caracteristics : LED Quantity 300leds Input Voltage 12V Power 72W/5M Cuttable Every 3LEDS Package 5 ...
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1answer
42 views

Is my circuit analysis correct in this problem?

This is the problem: My solution: I'm new the delta-to-y and y-to-delta transformation, it is obvious we need to use them. I got the same answer but I'm a bit skeptical about my solution. Is my ...
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2answers
47 views

Could we remove the resistor in parallel with voltage source or in series with current source?

Although this question have been asked. But I want to ask again. I still doubt about it. It is written in "Electric Circuits (9th Edition) by James W. Nilsson, Susan Riedel". And if we remove it, I ...
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4answers
53 views

How greatly can heat increase resistance?

A conductor has a resistance of 0.001 Ohms, at room temperature, by increasing the heat x100 degrees Celsius how greatly would that effect the conductor's resistance? I'm trying to find the ...
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1answer
60 views

Output resistance of Emitter Follower

I have to measure \$R_{in}\$, the input resistance seen by the signal. It was told me, that the quickest way is measuring the voltage gain using oscilloscope, insert a resistor before \$R_B\$, ...
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1answer
70 views

Continuous current capacity of this conductor?

How much current can a copper conductor that is 2 meters long, 0.003m thick, and 0.00045m wide continuously carry? Also, the resistance is about 0.02 Ohms.
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2answers
482 views

Can't find the equivalent resistance in this circuit

I'm trying to self-study this problem. This chapter explained the delta-to-y transformation but I can't seem to find one here. My best guess is that both resistors on the right are short-circuited ...
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0answers
52 views

How to know if a Resistor is bound or unbound by another Resistor? [closed]

I am new to Electric Circuits Analysis. And I am confused by some of the concepts of finding Equivalent Resistance of whole circuit. I am able to find simple or a little complex ones but I am totally ...
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2answers
32 views

Confusing Parallel/Series Arrangements in Application of Thévenin's Theorem

I'm learning from Paul Scherz's Practical Electronics for Inventors (2nd ed.) and I've become confused at what was I thought I was comfortable with: namely parallel and series resistors. The offending ...
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2answers
71 views

Internal resistance of signal source

It was told me that a signal sent to the circuit can be rapresented by \$V_{sig}\$ and \$R_{sig}\$, where \$R_{sig}\$ is the internal resistance of signal source. Now, let's consider that we have a ...
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1answer
49 views

Calculating the Output Resistance of a Widlar Current Source

I'm currently struggling to understand the small signal equivalent used in the following calculation: http://en.wikipedia.org/wiki/Widlar_current_source#Output_impedance My problem is: How come they ...
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3answers
146 views

How to detect a change in resistance?

I would like to have a circuit that can be controlled by two variable resistors, and it should use the value of the "most-recently-changed" resistor. How can I find out when one of the variable ...
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1answer
55 views

Minimum AWG of a battery wire

I have a 3.7V one-cell polymer battery 350mAh 25C. It's linked to a board over a 50mm wire. What would be a good AWG diameter to ensure a maximum voltage drop inferior to 2%?
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2answers
301 views

Trouble finding the R(equivalent) in this circuit

I started studying Electric Circuits one week ago so this material is new to me. I was trying to solve this problem from the book but I had some difficulty: My analysis: The equivalent resistance ...
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2answers
316 views

For the resistor circuit shown in the picture, what must be the missing resistance to give a total resistance of 252 ohms?

After my calculations, I keep getting 1100 ohms, but the back of the book is saying 85 ohms. 85 seems to fit in better with the other numbers, but I can only get 1100 to add up. Here's my ...
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1answer
35 views

Output impedance of a differential line receiver

Let's say I have an INA134 (http://www.ti.com/product/ina134) from Texas Instruments in my design. I want to take the output of that IC and feed it into a resistor network which can have a flexible ...
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1answer
40 views

Do Cable Connectors/Terminal Blocks impact power requirements?

I am planning on using a bunch of spare ego-T parts to build some mods and was thinking of hooking some AA battery block via some Cable Connectors/Terminal Blocks to an LED, Button and 510 Threaded ...
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2answers
97 views

What is the difference between the substitution principle and Thevenin theorem?

The substitution principle (as seen in this book; in italian, sorry) Let A and B be any two part of an electrical network with voltage and current sources and only resistances, connected by ...
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2answers
43 views

Max temperature of PTC heater, need tip

I have some difficulty reading specifications for PTC heaters, more specifically the ones on here. I understand that a PTC heater does not, inherently, rise above a specific temperature. In the ...
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1answer
57 views

Circuit breaker vs. electric heaters

Let's have a household with 230 Volt AC supply. What happens with the current if I start to gradually activate more and more (purely) resistive loads, like electric heaters and ovens? Because I=U/R, ...
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2answers
82 views

Heat output element

I'm building a little quiz game in Arduino and I already have it displaying a multiple choice question and people can answer by pressing pushbuttons. But anyways now I wanted to know if it's possible ...
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0answers
40 views

Analyse data discrepancies: Efficiency of wire vs current

Please help me explain why the efficiency of the wire does not follow a distinct path (ie R^2 value is low). Graph 1 Efficiency of wire vs current: http://postimg.org/image/p49bzm4ab/ Is is to do ...
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1answer
51 views

Explain this line of working when solving for the maximum power of a load resistor

Please, can you explain this line of working from the maximum power transfer theorem: For maximum power dissipation in the load, the condition given below must be satisfied $$\left. ...
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1answer
45 views

Inductor value given in OHM/Amp

I've been trying to figure out the inductance in Henries from a schematic of a Rabbit Microprocessor development board, however, instead of finding an inductance value over the components in question, ...
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3answers
58 views

Strength of a pulsed electromagnetic field

Forgive me if my question sounds a bit naive: I have built a coil (no solid core) out of an insulated copper wire, and I calculated that it has 8 ohms of resistance. I tried it and it gave me the ...
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2answers
119 views

Check my math: Calculating the size of extension cord needed

I think I've done this right, but I don't trust myself. Will you check my math and see if I'm right about this, or correct my error if I'm wrong? The facts I have a device (A Yamaha Stagepas 400i ...
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1answer
81 views

What is a 'normal' resistance level for a closed switch?

In a closed contact or a closed switch, theoretically, the resistance should be zero, but in actual measurements the resistance is very close to zero but not zero. So my question is: What is a ...
2
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2answers
164 views

High resistance voltage divider

I am trying to create simple variable voltage divider circuit, with several constraints that are causing me to look for alternative solution. Constraints: The input voltage is 1.5 V Maximum R1 is 5 ...
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1answer
89 views

Russian variable resistor datasheet

Can you please help me find datasheet for this 2.2 ohm variable resistor. I want to know if it can tolerate 20 amps. If you recognize the logo that would help a lot.
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2answers
98 views

Measuring current around 20 amps

I have an electrolyzer that works with car battery (12 volts DC) and draws current around 15 amps. I have a digital multimeter that can measure 10 amps at most. So how can I measure the current? Maybe ...
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3answers
119 views

Why is voltage higher at positive wire instead of negative wire in this example?

If electrons travel from "-" to "+" and voltage decrease going through resistor why is voltage higher at positive wire instead of negative wire?
2
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2answers
165 views

Compute for resistance (Resistance circuit)

Hi how do you solve this problem? I am confused. simulate this circuit – Schematic created using CircuitLab Find \$R_{AB}\$, \$R_{CD}\$, \$R_{EF}\$, \$R_{AE}\$ I came up with this: ...
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7answers
264 views

Understanding resistance in open and short circuits

I am continuing to try to learn a little about Electronics and I came across the following problem for which I am not sure I completely understand the calculations. In other parts of the book, they ...
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3answers
66 views

How to measure the resistance of digital potentiometer AD5241 in circuit when power on

I have designed a transimpedance amplifier including a digital potentiometer AD5241. The circuit is showed below. I want to test the AD5241 to make sure it works as designed. simulate this ...
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0answers
33 views

Solar charger under rapidly varying conditions/impendance

My solar equipment consists of: Solar panel capable of: 20V Peak / 3.6A Peak Li-Ion Battery pack: 8.7V, 9Ah, (2S3P setup) My solar charger setup consists of: 5A DC-DC BUCK converter (XL4015) ...
4
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6answers
239 views

Given a known power supply, what are safe ranges for the volts/amps/ohms of connected components? [duplicate]

I'm new to hardware and am coming from a software background. I have an SoC that will be powered by a supply generating 5V and 1A. I'm trying to figure out what are the safe ranges of volts/amps/ohms ...
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6answers
303 views

Why are resistor values constant in the face of changing voltage and current?

Small question, I see that resistors are labeled in certain increments (e.g 5, 10 50 Ohms), although a resistor outside of a circuit is completely without voltage and therefore current. Does this just ...
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3answers
104 views

Why doesn't linear resistance scale proportionally with the square of length?

I have an in depth question about basic proportionality of resistance. Why doesn't it scale with the square of length? I ask this because what is causing the potential difference on two leads is ...
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0answers
55 views

Inducing Eddy current in wet clothes

Is it possible to induce eddy current in wet clothes and dry them using the resistance heat generated? I don't want to connect any wires to the clothes.
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1answer
91 views

Understanding a power source's internal resistance?

I have a mechanical system that requires a certain amount of electrical power. Now, when I calculated everything I did not include the internal resistance. For example: I calculated that the ...
0
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2answers
86 views

Why can I put a resistor at either lead of this LED and still see its effects? [duplicate]

Just to add a little bit of context to the question, I am using an Arduino Uno and a breadboard. I have a 5V power source running to the positive (longer) lead of an LED (rated at about 2v and 20mA). ...
0
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6answers
95 views

How do I figure out the exact voltage and current needed for a part?

Whenever I look for parts in my local electronics store, I come across parts(e.g a speaker), that have just a power rating stated(e.g 2W). While I know how to calculate power,voltage, resistance etc, ...
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1answer
52 views

Proper resistor for simple circuit

I have a potentially stupid question, but I have no idea how to handle the problem. I want to use 9V battery with a diode that requires 5V. So I need a resistor. How do I find the resistance if (as ...
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2answers
58 views

Finding load resistance to achieve max power transfer

1) So, to find Thenevin equivalent resistance, R-Th, I disconnect R_L and disable the voltage source by shorting it out. ...
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3answers
107 views

Conductivity of plastic, wood and leakage current of laptops

Back around 2010, there were incidents where the surface of laptops have conducted 20-100V and have electrically shocked users. There is no doubt most of the newer laptops still conduct a continuous ...
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2answers
131 views

Using audio amplifier speaker output to drive an electromagnet

My first time here as a poster so forgive me if I make a misstep... I am building a coil (22swg enameled copper wire, about 500 ft), some 4in inner diameter of the bobbin, 1" wide, will have ~ 450 ...
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2answers
85 views

Use of inductors vs resistors

Why would we place an inductor in series with a lamp, rather than just a resistor? I'm sort of thinking it has something to do with being able to control voltage to the lamp, without effecting ...
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2answers
44 views

Non-parallel, non-sequential circuit

This is the circuit: I've simulated it and got a current of 30.76mA at the voltage source (5V). With this I've calculated the total resistance to be 162.5 Ohm. Each resistors is 100 Ohms big. But ...
0
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1answer
82 views

Two-port network: find fundamental parameters

What is the easiest method to find the ABCD parameters? I tried replacing the middle part of the circuit (R2,L,C) with an equivalent impedance and then finding U2 depending on U1, but it is very ...