Tagged Questions

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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2answers
105 views

Current capacity of wires

So this question stems from a previous question. Here Where from several tables one can see that the maximum current (Imax) is proportional to \$1/R\$ where \$R\$ is the resistance. (Or that ...
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1answer
43 views

Resistance and voltage drop conclusion [on hold]

Is it true that the higher the resistance the higher voltage would drop?
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1answer
22 views

How do I find the equivalent resistance using symmetry?

I know this could be solved using delta-to-y transformation, but I want to solve this using symmetry. Considering the middle line the symmetry axis this becomes: simulate this circuit ...
1
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2answers
84 views

How much current does a typical multimeter draw to measure resistance?

Assuming it's running on a 9V battery like most multimeters are, and the setting is on MegaOhms. How much current will be drawn from the internal battery?
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1answer
71 views

110v 220v do it work? [closed]

i bought hookah heater from amazon. this product link is ...
1
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1answer
33 views

definition of input/output resistance of a circuit

Is input resistance always a small signal parameter or is also defined for large signal model of any circuit? How do we model any circuit after we calculate its input/output resistances?
29
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6answers
3k views

Using a bottle of water as a resistor

Today, while drinking some water from a \$500mL\$ bottle, I started reading the info about the water and found out that the conductivity (\$\sigma\$) at \$25°\$C is \$147.9\mu S/cm\$. So it came to my ...
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2answers
58 views

Real equivalent of terminal resistance

I found in a book a scheme representing a terminal connection used in making an ammeter shunt (with the purpose of extending its measuring domain). I can't understand what the drawing at b) ...
0
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2answers
53 views

Are all solenoids waterproof?

I have an application where I need a solenoid to control a valve at the bottom of a tank. For unimportant reasons the valve needs to be inside the tank at the bottom. I was wondering are all ...
1
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0answers
69 views

High resistance (100Mohm) control using constant voltage or current source

I want to control resistance (100Mohm) programmatically. I found on this site that photoFET can solve this issue by sourcing constant current. From my understanding FET can give resistance control ...
0
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1answer
70 views

Thevenin's equivalent of Wheatstone bridge

I tried to calculate the Vos and Isc and both of them are zero..so the Thevenin's resistance is 0/0=undefined. How do I calculate the resistance when Vos/Isc fails,such like the Wheatstone ...
0
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1answer
73 views

Calculating total resistance for this circuit?

I'm very lost in my ECE class right now and I was hoping someone could help me out and explain what they're doing. I was asked to calculate the total resistance. After getting that, I was asked to ...
0
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2answers
58 views

Contactless electrical connection

I will have a carriage sliding over a round metal shaft and the linear bearings will not necessarily be conductive. I want to calculate the position of the carriage by measuring the resistance from of ...
2
votes
3answers
518 views

How do I find the resistance between three terminals?

I'm trying to self-study this problem and I found a bizarre problem with an unusual circuit. I have never faced this in all the problems that I have solved. What do they mean by finding the ...
0
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3answers
92 views

How to determine how much current and or voltage a given circuit “needs”?

My apologies in advance if I make any wrong assumptions. Say you have an outlet that is rated at 120V and 10A. My power adapter for my MacBook says it is rated at 16.5V and 3.65A max. How was it ...
0
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5answers
130 views

What would happen if an ideal voltage source was connected to an ideal wire?

I've seen it mentioned in discussion that an ideal wire doesn't exist (all wires have resistance), but even if it did, an ideal voltage source doesn't exist (all batteries have internal resistance); ...
0
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1answer
64 views

Calculating R with 2 resistors parallel

I've ran into a slight confusion. The equation for resistance in a parallel circuit should work for any number of resistors, I assumed. So when I'd have 2 resistors in parallel, total Rt would be: ...
1
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3answers
133 views

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
79 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 ...
0
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1answer
71 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 ...
0
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2answers
61 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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5answers
94 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 ...
1
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1answer
73 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\$, ...
3
votes
1answer
77 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.
4
votes
2answers
516 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 ...
0
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0answers
53 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
56 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 ...
0
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2answers
79 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 ...
1
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1answer
82 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 ...
0
votes
3answers
151 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 ...
1
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1answer
60 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%?
5
votes
2answers
322 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 ...
4
votes
2answers
333 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 ...
1
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1answer
38 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 ...
1
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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 ...
0
votes
2answers
111 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 ...
0
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2answers
48 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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votes
1answer
60 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
94 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 ...
1
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0answers
45 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 ...
0
votes
1answer
53 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. ...
3
votes
1answer
49 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, ...
0
votes
3answers
59 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 ...
2
votes
2answers
127 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 ...
0
votes
1answer
118 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
votes
2answers
180 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 ...
0
votes
1answer
93 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.
2
votes
2answers
114 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 ...
0
votes
3answers
125 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
votes
2answers
181 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: ...