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.
0
votes
2answers
177 views
basic math question about voltage, ohms, resistance
total n00b here. After working on several projects by copy & paste from other people's schematics and code, I'm finally digging in and learning some of the math to know what I'm doing.
If I have ...
3
votes
1answer
48 views
calculating resistance for LED strips to use as parking lamps and turn signals
I'm installing LED strips in my car's tail lamps to convert it from conventional bulbs to LEDs. I have a understanding of what I'm doing but not the complete knowledge to make the circuit work ...
3
votes
1answer
117 views
At what frequency will the reactance of a 1μF capacitor equal to the resistance of a 2kΩ resistor?
Here is my work:
\$ R = 2000 \Omega\$
\$ X_L = 2 \pi f L = 2 \pi (1 \mu F) f = 6.28\mu F(f)\$
\$f = \dfrac{2000 \Omega}{6.28 \mu F} = 318.471MHz \$
Does this look right to everyone?
1
vote
2answers
63 views
how many resistance do i need to safe the LED of PC814?
if i have a input of 5v (arduino HIGH) on the LED of a PC814, how is the value of the resistance that i must use before that, so i don't burn the led?
...
3
votes
1answer
37 views
Replicate thermistor behavior for second sensor
I'm working with an R/C electric motor that has a 10K thermistor sensor built into it, which is connected to a speed control that has basic thermal protection. I would like to build a secondary sensor ...
1
vote
2answers
303 views
Hardware to Detect EMG or Skin Resistance
I have been given assignment to design a device that can detect emg signal of Skin Resistance change while moving
fingers.
actually i need to track finger movements using some hardware containing ...
4
votes
1answer
92 views
Measuring very small changes in resistor network using current source
I am trying measure a very small change in resistance (approximately .400 Ohms), due to the the effects of connecting a large resistance in parallel with a network of smaller resistors essentially ...
1
vote
3answers
103 views
Selectable Voltage Divider Optimal Switching Point
I've built a circuit to measure an unknown resistance (over a large range) which is basically the following:
simulate this circuit – Schematic created using CircuitLab
Range_Select_1 and ...
1
vote
2answers
94 views
Is is possible to produce a resistance that represents the average of two thermistors?
For example, if I want to connect 2 thermistors to a thermostat in a circuit and then return the average resistance between the two of them to the thermostat's ADC.
-1
votes
2answers
90 views
Calculating equivalent resistance [duplicate]
How do I calculate the equivalent resistance between A and B?
1
vote
2answers
118 views
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 ...
8
votes
5answers
556 views
Resistors with ends of the same colour
I know the values of resistors if they are gold-colored at the end. When both ends are the same, such as brown-o-p-brown and red-x-y-z-red, I am in problems. How to know which side has the last colour ...
0
votes
2answers
119 views
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 ...
4
votes
3answers
188 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 ...
2
votes
1answer
64 views
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 ...
5
votes
2answers
88 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 ...
3
votes
2answers
92 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 ...
0
votes
2answers
111 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 ...
4
votes
1answer
101 views
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 ...
6
votes
2answers
133 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. ...
0
votes
1answer
137 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 ...
1
vote
1answer
86 views
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 ...
-6
votes
2answers
149 views
Battery with most mAh that outputs between 1 and 1.5v? [closed]
I am looking for a rechargeable battery between 1 and 1.5 volts that can provide this voltage for the longest amount of time (most mAh). Any suggestions? Thanks.
-2
votes
5answers
517 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 ...
3
votes
3answers
154 views
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 ...
3
votes
2answers
142 views
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 ...
1
vote
0answers
50 views
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 ...
1
vote
3answers
216 views
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?
6
votes
3answers
352 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.
4
votes
4answers
7k views
How do I calculate the resistor value for a simple LED circuit?
I have a simple circuit:
The max rating (current) of the LED is 30mA.
How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 ...
16
votes
4answers
538 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 ...
1
vote
1answer
84 views
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 ...
4
votes
1answer
446 views
How to test internal resistance on small lithium polymer cell?
I'm coming from a computer science background, and will be writing some software to automate battery testing. I have background in math, but little to none in physics or electronics. Please consider ...
-6
votes
1answer
97 views
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
2
votes
1answer
286 views
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 ...
0
votes
6answers
354 views
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 ...
-1
votes
1answer
135 views
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 ...
4
votes
6answers
276 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 ...
4
votes
4answers
1k views
Precise Resistance Measurement Techniques
This question is inspired by some basic questions on resistors I've read here lately.
What's the most accurate/precise technique for measuring the value of a resistor you can think of? What level of ...
-3
votes
1answer
332 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 ...
1
vote
1answer
110 views
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 ...
4
votes
1answer
97 views
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) ...
9
votes
1answer
995 views
How do you calculate the noise of an op-amp circuit?
I think I know how to do this, but you can find a lot of different instructions and calculators online that contradict each other. I have yet to find a clear, concise procedure for calculating the ...
4
votes
4answers
276 views
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 ...
0
votes
2answers
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 ...
2
votes
2answers
181 views
What is the equivalent thevenin resistance of a digital output port on an Arduino Uno R3
How would I determine the thevenin equivalent resistance?
1
vote
1answer
64 views
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 ...
3
votes
1answer
142 views
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 ...
17
votes
2answers
927 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 ...
4
votes
4answers
773 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 ...
