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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37 views

Voltage Divider, increasing resistor value for solar tracker

I am working on a solar tracking device based on arduino and I am using LDR's (Light Dependent Resistors) as voltage dividers. The wiring is similar to this: The problem I am facing is that the ...
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2answers
55 views

Working out current, voltage and resistance in a Bridge circuit?

This community is so helpful, my thanks go out to any comment I got with helpful advice. Here's another homework problem. I've tried working most of it out, but I have a feeling that I'll have to ...
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4answers
116 views

How would you solve this resistive network?

simulate this circuit – Schematic created using CircuitLab I'm not really sure how to solve this. I can't see any series or parallel connections. I need to find the Total resistance, V1 ...
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4answers
48 views

What is equivalent Resistor different Resistors put them in series or in parallel if they have a different wattage and different resistance?

What is equivalent Resistor of two this different Resistor put them in series or in parallel if they have a different wattage and different resistance? In practice somtimes we have a resistor with ...
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1answer
42 views

Controlling an electric water heater

I'm trying to control the temperature of water heated electrically. On devices sold commercially I see that temperature is not being controlled, and the heating elements are either turned on or off ...
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2answers
119 views

16 segment LED sparkfun resistor help

I am quite new to this and am struggling to read through the data sheets of the Sparkfun 16 segment display, datasheet here. I have managed to get all of the LEDs wired up through a LED driver, with ...
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2answers
66 views

The purpose of voltage-dividers in op-amp feedback?

simulate this circuit – Schematic created using CircuitLab So, here we have a typical op-amp with negative feedback. The non-inverting input is at virtual-ground, and if the input is ...
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1answer
41 views

What is variable resistors? [closed]

What is the role of variable resistors in the electric circuit? Please give an example of electric circuit for variable resistors.
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1answer
43 views

Detect open or closed circuit via USB sensor

I have a relay which I need to detect the state of (similar to this question but no current flow) and would like know what the easiest method would be to detect the state via USB and Raspberry-pi. I ...
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2answers
80 views

Why is inductor completely canceling out current?

I used this calculator to determine that my hand-turned inductor has an inductance of approx. .5 uH. simulate this circuit – Schematic created using CircuitLab When I measure this ...
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3answers
94 views

Measuring the inductance of a coil?

I have a hand-wound coil I'm using in an LC Tank circuit. Using my multi-meter, I found out that the coil is drawing .6mA at 9v. Using Ohm's Law... $$R = V/I$$ $$R = 9/.0006$$ $$R = 15kΩ$$ Is there ...
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2answers
90 views

Voltage drop through a resistor using Ohm's Law?

I'm having a very hard time comprehending basic Ohm's Law. I was recently watching a video on the operation and use of Operational Amplifiers, and was completely lost because I couldn't understand ...
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4answers
72 views

Calculation of the input resistance of an op amp circuit

After I calculated that $$v_s=v_u\left(\frac{R_1}{R_1+R_2}\right)$$ I have to calculate the resistance seen by the voltage generator \$v_s\$. My book, without any calculation, says it is: ...
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3answers
209 views

Can I use a 5% tolerance resistor instead of a 10% tolerance resistor?

can I use a 5% tolerance resistor instead of a 10% tolerance resistor? It is for an organ from the 60's. All resistors stated in Schematics are 10% 1/2 watt. But I can't find a 6.8k 1/2watt 10% ...
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2answers
65 views

wire gauge for solderless lithium batteries in series?

I am making a prototype lithium battery of 2kw / 40 amps. it's 8p14s, and every bank of 8 parallel is joined with copper sheet in solderless contacts. I have bought some 0.1mm thick copper sheet and ...
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0answers
58 views

Hissing noise coming from light fixture [migrated]

I have a light fixture in my bedroom with three 60 watt LEDs in it. I can hear a loud hissing noise coming from each light. I'm almost positive it's because there is just too much power flowing into ...
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3answers
63 views

Is it reasonable for a potentiometer to have a minimum of 1.3Ω?

I purchased a 25Ω linear potentiometer, and found that the minimum resistance is 1.3Ω 0.9Ω. I expected that the minimum would be closer to 0Ω. Is this typical? Should I return the potentiometer as ...
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0answers
42 views

How can I add a resistor in parallel to a rheostat while keeping it linear?

I have a 25Ω linear potentiometer wired as a rheostat. I would like a range closer to 5Ω, so I added two 10Ω resistors in parallel. This gives me a range of 0 to 4.16Ω which is just fine, but the ...
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3answers
1k views

Powering a device by USB?

I would like to power a device via the 5V USB port on a computer, because I will also be communicating with the computer via the USB data cables. I know that USB ports provide 5V, but from what I've ...
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1answer
72 views

Maximum Amperage AA Battery

I have a simple question. How many amperes can an AA battery draw? I'm studying electronics and looking at the Ohms law: V=IR and taking as an example a 1.5V AA alkaline battery, and considering the ...
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2answers
112 views

Is there a way to measure three discrete resistances simultaneously?

I'm working on a test box for fencing body cords. These cords are always 3 wires, and will plug into a box that I'm still designing. The test box I currently use connects to a multimeter and has a ...
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1answer
45 views

Filtering noise off of PWM signal

I am trying to measure the resistance of a nichrome wire that has a PWM (1000Hz and different duty cycles between 0 and 100%) voltage applied to it from a 5.0V regulator. The setup I have in mind ...
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2answers
43 views

e12-table - replace resistors

Is this the table of 12 resistor series? 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 http://sv.wikipedia.org/wiki/E12_%28resistorserie%29 And if I have a resistor of let say 1670 ohm - how do I ...
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2answers
129 views

Trouble converting 12VDC incandescent to LED: lack of resistance

I'm converting two, independent, incandescent bulbs (OEM 212-2) fixtures to use LEDs for automotive map reading. Each incandescent bulb (12-volt/system) measures 1.5 ohms with a meter; however, there ...
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1answer
65 views

Is there a way to find this resistance? [duplicate]

I have done thevenin analysis on a larger circuit and have gotten the result below. I need to find the value of RL. Would I use thevenin again? But that would give me the same result because I would ...
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2answers
77 views

Grounding a wire using a chunk of metal?

So I've made a complex LED grid and it works but has ghosting in some of the rows. I've given up trying to work out the reason why, but have noticed that when I touch the SCLK wire, or connect the ...
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1answer
65 views

Voltage used up by a transistor and shift registers

i am on a project 8x8x8 LED cube and I am stuck on the value of register i should use. Talking about single layer I am using 2N5296 transistor for common cathode and 8 shift registers for controlling ...
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0answers
36 views

fuse metal alloy with high springiness?

Is there a fuse alloy that would have the same springiness as this except with a little wire that comes out and that plugs into something, so that it could be machined and pressed from one single ...
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2answers
46 views

Potentiometer with No Minimum Resistance

I'm looking to create a variable current regulator with the LM317 using 1-turn pots. I know that I am going to need to have a resistance of 1.25 Ohms to have a current of 1A, which I want to be my ...
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1answer
21 views

Max Voltage of Electrical Stimulator for Cardiac Tissue Bioreactor

I'm designing a bioreactor that will electrically and mechanically stimulate cells in media in an incubator. I'm using monophasic, square waveforms and have a max stimulation level of 12V/cm, else ...
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1answer
48 views

How does switch interfacing work?

This is a basic question, but I don't have a background in electronics so I find it difficult to wrap my head around the concept of how current flows. I have chosen this simple example of interfacing ...
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1answer
67 views

Measure inductor coil's resistance using multimeter

simulate this circuit – Schematic created using CircuitLab Above is the set-up of my simple experiment to determine the inductance of an inductor. The voltage across resistor R (5 ohms) ...
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1answer
58 views

What determines the amount of power sent to a device?

I have various devices that draw amount different amounts of power from a micro power connector. If I have a 240V socket plugged into a device which draws 4W of power, does this mean that the power ...
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0answers
42 views

modeling AC resistance proximity and skin effect using LTSPICE

I'm designing an air-core loop receiving antenna from <1Hz - 50kHz. Is there a way to approximately model the skin/proximity effect using lumped circuit parameters in SPICE software? I think you ...
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2answers
258 views

How do I work out what resistor to use?

I am trying to work out what resistor to use in a circuit. The circuit is a series circuit. The power to the circuit is 5.5V, with a switch, which connects to a GPIO pin on the RasberryPi. I believe ...
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0answers
56 views

How does temperature affect the performance of an SMPS?

I have an SMPS (laptop AC adapter) rated for 180 W that is presently operating at capacity. The output seems to be limited by internal resistance, but I can't really tell. I'm trying to get it ...
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0answers
59 views

Mosfet small signal input resistance from source

Considering the T model of MOSFET for small signals I want to obtain the input resistance from source to gate. simulate this circuit – Schematic created using CircuitLab The current ...
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0answers
44 views

Is the armature resistance of a DC motor the sum of the resistance of each winding?

I am aware of a number of methods of measuring the armature resistance of a DC motor including locking the rotor, giving a fraction of the rated voltage, measuring the current and calculating the ...
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2answers
89 views

Output Voltage Swing vs. Load Resistance of an Op Amp

What does the "Output Voltage Swing vs. Load Resistance" signify? Lets say I want to get a gain of 400 from an op-amp. I can use any one of the following combination Gain = -(R2/R1) Case 1: R2 = 400 ...
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1answer
43 views

electret microphone dynamic impedence

how much is the dynamic impedance/resistance seen from a electret microphone? I am trying to design a microphone preamp and need to know seen resistance in small signal from the signal source ...
3
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4answers
493 views

Formula to find out the resistance per meter of a specific gauge of wire if I already know the resistance of a different gauge of wire per meter?

So if I know a 30 gauge wire's resistance at 1 meter, how can I figure out the resistance of a 29 gauge wire at 1 meter long of the same material? Or 5 gauge, or any other gauge? I need a formula, not ...
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1answer
201 views

Does the MOSFET Rds(on) value really matter?

I am using MOSFETs in the ubiquitous RAMPS 1.4 Arduino shield for 3D printing use. The MOSFETs switch the voltage to the heated bed and the hotend (where the filament comes out). I need to replace ...
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2answers
51 views

Finding input resistance for this circuit

How do I find the input resistance for this circuit. I think it should be infinite but not able to analyse properly. Thanks.
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2answers
93 views

Voltage vs current vs resistance - did I understand them right?

I'm currently getting started to learn about electrical engineering, and I'm having some difficulty separating voltage from current. I have seen a couple of times that a battery is compared to two ...
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1answer
110 views

IRF540 power Mosfet 12 volt motor gate resistance

I have a IRF540 power Mosfet driving a 12 volt motor. Currently I am using a 100 ohm gate input resistor, It is working fine. What I want is the maximum gate resistor value that I can use and still ...
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1answer
90 views

How to create a simple circuit with your body

I recently visited a museum with my son, and we both enjoyed an exhibit where there was a partially completed circuit that was completed when you touched the two end points or joined hands and each ...
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5answers
141 views

The path of least resistance

i always knew that current will take all paths, even the other post on this forum said so, but i was doing this RC circuit today where the resistor and the capacitor are wired in parallel, i was told ...
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3answers
96 views

Calculating voltage in diode circiut

Could you explain to me why U_out is -4,4V and only 3rd diode is open in the following example? Given that R is 10kOhm. My physics resistant brain tell me that voltage at each anode is is 10,15 and ...
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1answer
91 views

What is the equivalent resistance in this part of the circuit?

I broke the circuit down into as basic as I can take it, and I know what X and Y are, but I can't figure out the equivalent resistance of the circuit in the middle. It seems to me like the current ...
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2answers
87 views

Resistance as a function of base voltage in a transistor

In this very interesting introductive video https://www.youtube.com/watch?v=CkX8SkTgB0g, I learned that a transistor is basically nothing more than a resistor whose value changes accordingly to what's ...