# 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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### What kind of Relay Reacts to Ohms?

I need to connect a relay to my old truck to turn on the "soon to add" electric fans. The ECM has an engine coolant temperature sensor that uses the output resistance to determine coolant ...
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### Electron flow due to impedance?

In the basic electronics lecture today not only I but whole class became confused by an explanation of our teacher that in high impedance value electrons movement become easier while in low impedance ...
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### How to detect and identify multiple points of contact

I am looking for a way to detect & distinguish multiple points of contact from force or pressure. I have asked a related question at the URL listed below: How to encode a large number of digital ...
111 views

### Voltage distribution between components

I often see the same method for computing voltage distribution in electronic circuits implying components whose V-I curves are not trivial. For example, in a circuit implying a resistor and a LED ...
140 views

### What impedances do graphics cards expect on H-Sync and V-Sync for VGA monitors?

I have a graphics card for a laptop whose driver kills itself if it runs for longer than two minutes with no external monitor attached. To solve that, I decided to make a sort of dummy plug that would ...
143 views

### How to design voltage ladder on ADC for non linear purposes

I'm designing a 4-bit ADC for a project that receives a reference voltage that ranges from 1.0 to 1.25. The problem is, it's not a linear variation, as in 0001 can be 1.05V, 0010 1.1V but 0011 could ...
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### What is the origin of the “r” in resistance measurements? [duplicate]

In a post to the diyaudio forums, www.diyaudio.com/forums 67232, I see terminology that are likely to be measurements of resistance: "0r1", "1r0", and "10r". I am thinking the "r" there means a ...
151 views

### Working out thickness of a copper wire

This was one of the questions for the repetition paper before the test. "A lit light bulb has a resistance of 1320 Ω. It uses tungsten as a filament, and when hot, has a resistivity of 0.92 µΩm. ...
190 views

### How does this heavily oxidized copper-to-steel joint work in earthing?

Wikipedia article on grounding features this photo: Here's a close-up of the joint: Clearly the steel rod is heavily oxidized and the copper wire is oxidized. The clamp is coated with something ...
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### What's the input resistance of an opto-isolator?

I need to sense if a 48 volt power supply is supplying voltage or not, I plan on doing this with a opto-isolator and I am happy with the output circuit from isolator. Can I connect the input of the ...
2k views

### how to calculate total resistance in circuit with parallel and series resistors connected

A battery of EMF 8.0 V and internal resistance r = 1.0 – is connected to an external circuit as shown: I need to find out the total resistence and my problem is that I dont know which resistors ...
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### What easily acquirable material changes its resistance when heated?

I'm trying to build a Resistance Thermometer that varies current/voltage output when heated. It has to be DYI, I don't want to buy anything done, only something like a light bulb, and this has to be ...
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### Mathematical approch to measuring current, voltage and resistance of mixed series and parallel

If there is a circuit like the one below, where all resistors are 1k ohm, how does one determine the currents? The voltage sources are all 10 volts. The problem I am having is that I do not know if ...
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### How do construct a electrical resistance tomography apparatus

Im interested in constructing an electrical resistive tomography setup to image underground structures. While I somewhat understand the principle, I have found limited information on design and ...
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### Does a resistor in an AC circuit produce the same heat as in a DC circuit?

Does a 1k ohm resistor produce the same heat in a AC circuit which has an rms voltage of 10 volts (60 hz.) as it would in a 10 volt DC circuit?
1k views

### Why do diodes have a voltage drop?

Is resistance what makes a diode have a voltage drop? Or is it impedence? If it is electrical energy being converted to light, please tell me what this effect is called.
733 views

### Why does water short out PCBs? (i.e. Why doesn't electricity follow the path of least resistance?)

If copper is more conductive than water (at any reasonable PH), submerging copper electronic circuits in should have no effect, as the electricity should continue to follow the path of least ...
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### Building a pocket theremin

I'm putting together a kind-of sort-of theremin (this one in particular http://www.popsci.com/diy/article/2008-04/build-pocket-theremin-cheap) and I'm looking to make a bit of a change to it. What I ...
590 views

### Resistance to Digital converter

I am trying to make a digital ohmmeter on a parallel port interface that can measure resistance with at least 95% accuracy. I have tried a 555 timer monostable assembly which generates a pulse with ...
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### why there is resistance present between Power supply terminals even in off condition?

I wanted to know why there is preasence of resistance between poer supply terminals even when power supply is in off condition? Thanks Mayuresh
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### Wye-delta transform derivation

I have been reading about the Delta-Wye and Wye-Delta transforms for resistors, and I was curious as to how the equations for the Delta-Wye and Wye-Delta transforms are formed. I managed to isolate ...
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### Z-parameters. Is Z12*Z21 always greater or equal zero if a circuit has only resistors? [duplicate]

Possible Duplicate: Is equivalent resistance always lower if we add a resistor to a passive electronic circuit? Since my last question was probably badly formed and misunderstood this is a ...
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### Is equivalent resistance always lower if we add a resistor to a passive electronic circuit?

How to prove that equivalent resistance of any passive network is always lower (or equal) if we add a resistor between arbitrary two nodes? Note that this is not necessarily a parallel circuit, 2 ...
325 views

### Would a 100k ohm resistor or motor emit more heat

Would a 100k ohm resistor produce more heat than a motor that had the same resistance? +|---------(100k ohms)---------|- +|---------(100k motor)--------|- Both circuits have the same amount of ...
503 views

### AC and DC Resistance [closed]

I have a few questions regarding my task of calculating AC and DC resistances: If a cylindrical conductor is made of two different materials, would the conductor's effective resistance be the ...
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### Need to know the exact values for sense resistor, resistors in op-amp and power supplies

I am computer scientist and I don't know much about electronics. In my master work, I have to design a circuit that measure the energy consumption of receiving single tweet from mobile ...
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### Can you pass resistance through analog mux?

I have a digital potentiometer that I want to calibrate by sending in my commands and then measuring what the actual resistance is. However, the resistance from the digital pot is (obviously) ...
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### More than 2 resistors in parallel

Most people know the formula for the total resistance of parallel resistors: $\dfrac{1}{R_t} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + {}...{} + \dfrac{1}{R_n}$ If there are only 2 resistors, that can ...
2k views

### Potential difference across one resistor with and without a known current?

Okay imagine you have a voltage supply of 10V and one Resistor of 5 Ohms. Now find the current : I=5/10 = 0.5A So potential difference across that resistor : V=IR=10V .. which proves this statement ...
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### What is the equivalent thevenin resistance of a digital output port on an Arduino Uno R3

How would I determine the thevenin equivalent resistance?
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### Find total resistance

The book (Principles of Electric Circuits by Thomas Floyd 9th edition, International edition) says it's 1.955k Ω... When I calculate I get (R1 || R2) + (R3 || R4) + R5 = 3.38k Ω... Thanks for any ...
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### Impedance of 4 conductor system spaced horizontally apart

I have 4 cylindrical conductors spaced equally and horizontally apart. How can I calculate the magnitude of Impedance (Z) using the Skin effect and Proximity effect? I'm looking for an equation that ...
1k views

### Why are lightbulbs considered resistive load?

A lightbulb (a plain old incandescent lamp) is typically brought up as an example of resistive load. Yet the filament is actually made of several feet of very thin wire cleverly coiled to form a ...
1k views

### Driving LEDs at long distance

I'm looking to drive 52 LEDs (datasheet), around a large inflatable tent. The LEDs have a forward voltage of 3.3V, at a maximum of 20mA. I'm thinking of using the NXP SAA1064 I²C 16-channel LED ...
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### Is there an out-of-the-box solution for measuring low resistances?

I have a microprocessor project where I need to measure resistances between .1ohm and anywhere above 10ohm and I need to do it about 1000 times per second. Guessing from the number of tutorials I've ...
697 views

### Is this resistor needed in this opamp circuit?

I'm looking at the datasheet of the MCP6241. There's this schematic: The op-amp has a input bias current of 1 pA, and $10^{ 13}\Omega$ input impedance. Is resistor Rz still needed then?
943 views

### Help with understanding Current, Voltage and Resistance

Is my analogy correct: With a highway as an example, would Resistance (ohms) be the number for lanes in one direction Current (amps) be the density of cars on the road Voltage (volt) be the speed ...
388 views

### How can I meet these PCB design conductivity/isolation requirements?

The specifications required are as follows: The resistance between ground pins on a connector and the case (chassis) ground should be less than 3 Ohms. The resistance between any other signal on the ...
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### Why do batteries not last as long in a cold environment?

I know that batteries don't lase as long when they are used in a cold environment, but why is that? For normal conductors resistance decreases as temperature goes down, so shouldn't the internal ...
3k views

### How to calculate current and voltage draw of a single resistor circuit?

If I have a single 270 ohm resistor connected in a circuit to a 3.3V 50mA power supply, how can I measure the voltage and current for the resistor? I'm familiar with Ohm's law V=IR, where V is the ...
508 views

### How does audio get transmitted from my iPod to speakers?

I need some help understanding a simple concept. I understand that my iPod/any other audio device sends electrical signals to my speakers/headphones. From my research so far, an analog signal is ...
140 views

### what is the resistance of hydrogen?

If I were to connect a bettery to the two sides of a container that contain only hydrogen gas, and its not dense (it's pressure is one atmosphere), what would it's resistance over the length of the ...
796 views

### Requirement to display 3 mm LED by 220 V AC supply

I want to power a single 3 mm LED by a 220V AC source. For this I think I need one LED, one resistor and one capacitor. I don't know the needed resistor value and circuit diagram. The circuit also ...
536 views

### Calculating Rout of a bjt while using correct RL

I'm studying the notes of my professor of electronics, and I'm noticing an inconsistency of $R_{L}\:$ compared to what I've seen around in books and on the web. Here's what is considered ...
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### How do different kinds of motors behave electrically under operation?

This is sort of a follow-up to this topic: Overclocking my toothbrush I have since measured some numbers with my DMM. Remember this is a tiny brushed DC motor in a \$5 toothbrush that I am driving ...
409 views

### Electronically switched decade resistance box design

I'd like to design a decade resistance box that uses a microcontroller to control the resistance. Would it be possible to switch between different valued resistors using transistors? (or another ...
195 views

### Designing a water boiler?

I know this is very basic, sorry. But what material do I need to have enough resistance to boil water with the 120V household outlet? Thank you
261 views

### Understanding electric power

While in a mood to purchase a Peltier strip, I visited the amazon page which stated the specs of a Peltier thermoelectric cooler, one stated 12 V and 92 W and other one stated 12 V and some 77 W. As ...