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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1answer
29 views

Series Damping Resistor for Low-Speed USB

The USB 1.1 spec gives well-defined \$V/I\$ characteristics for full-speed output drivers, which can be used to find the series damping resistance, \$R_S\$. The low-speed output schematics also ...
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1answer
39 views

Input/output pin resistance for an AVR microcontroller

For example, when driving a logic-level MOSFET directly from a microcontroller, what is the smallest gate resistor that can be used? Specifically for AVR microcontrollers; i.e. this datasheet, the ...
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1answer
143 views

Maximizing force of magnetic mass accelerator

I am planning to build a coil gun to fire small neodymium magnets out of a pipe. For this I am planning to use a large 400 Farad 2.7 Volt capacitor. I am wondering how many coils of wire I should ...
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2answers
100 views

Regarding the design of a basic voltage divider

I've just entered the fabulous world of circuitry and was wondering about the design of voltage dividers. I understand their function and formula quit well, but was wondering about the actual ...
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0answers
40 views

Calculate a resistance - help with the signs

I have a problem with \$R_i\$, isn't it \$-\frac{v_i}{i}\$? My book report it in the solution as \$\frac{v_i}{i}\$ . Why? I know the question may seem trivial, but I'm a newbie to this field, so I'd ...
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3answers
335 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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0answers
51 views

MOSFET impedance scaling

Suppose I have two devices. Both devices have the same gate length \$L\$ but device A has a much smaller width \$W\$. Device A has \$R_{\text{on}} = 1K\$ and \$R_{\text{off}} = 100G\$. Device B has ...
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1answer
40 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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1answer
54 views

Whether Internal source resistance will have effect on the circuit

Calculate the voltage gain for the network of Fig. 3.12 if the source has an internal resistance of 100 in series with Vi.Vi=500mV,R= 1K ? For this problem I had tried a solution but I am not ...
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1answer
79 views

resistance measurement problem with digital multimeter

I accidentally caused a short circuit with DMM common lead while measuring 220 AC voltage. then when I tried to measure resistance it gives me a reading of 3500 ohm while there is no resistor ...
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2answers
84 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
97 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
54 views

Charge pump output resistance

I am designing (simulating in LTSpice and building on a breadboard) a charge pump to power my numitron tube. I need to get ~15-20 V out of 3.3 V. The circuit is as follows: simulate this ...
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2answers
69 views

How do we predict if power loss will increase or decrease in a DC circuit?

I want to know whether it is possible to predict if power loss will increase or decrease in a circuit with a fixed EMF, a fixed resistor in series and a variable resistor in series. If we change the ...
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2answers
143 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
44 views

Resistance and voltage drop conclusion [closed]

Is it true that the higher the resistance the higher voltage would drop?
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1answer
29 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 ...
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6answers
163 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
94 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
79 views

110v 220v do it work? [closed]

i bought hookah heater from amazon. this product link is ...
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1answer
38 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?
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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
61 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
54 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 ...
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0answers
73 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 ...
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1answer
105 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 ...
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1answer
78 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 ...
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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 ...
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3answers
535 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 ...
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3answers
101 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 ...
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5answers
132 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); ...
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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: ...
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3answers
142 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 + ...
1
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1answer
85 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
votes
1answer
74 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
72 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
102 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
78 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
82 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
526 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
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
74 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
90 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
123 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
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3answers
157 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
62 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
339 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
344 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
41 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 ...