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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6
votes
1answer
516 views

What does “OC” mean?

My Bluegiga WT-32 manual ("Stereo CODEC ADC characteristics" table) says: Allowed Load --> Resistive, min.:16(8)Ω , max.: OC What does OC mean in this case?
0
votes
0answers
46 views

Minimum AC voltage that causes nerve damage?

What is the minimum AC(50-60Hz) voltage that can do harm/nerve damage? I know that a few hundred volts (even 100?) has been documented to cause nerve damage that resembles a crush injury. I also know ...
0
votes
2answers
52 views

What is the strain gauge resistance variation of a 3-wire loadcell?

A 3-wire loadcell have two strain gages with a no load resistance of R. When a load is applied, the resistance of one strain gauge will change to R+dR and the other will change to R-dR (because one ...
-1
votes
0answers
50 views

Stable current?

A large conductor that carries massive amounts of current at extremely low resistance(micro-ohms), now back EMF is induced that is really large. Let assume V = 0.2 volts and -V = 100 volts, and I ...
1
vote
2answers
61 views

Why do you need a thicker wire when wire length increases?

Question: So far I've found that the thickness of the wire influences the resistance. A thicker wire has less resistance. Also, the length of a wire has a linear correlation with the resistance. 2x ...
-1
votes
2answers
71 views

If resistance is very high?

$$ V = IR $$ If there is a conductor with very low resistance, moving in a magnetic field, will it induce low EMF = IR? And a high current? Im confused at that point... Lets assume a conductor ...
0
votes
4answers
112 views

How does a potentiometer work?

A lot of places where I've read explanations about potentiometers either go into so much detail or they're so superficial that I don't understand the actual concept behind it. How would you easily ...
1
vote
1answer
46 views

Minimum electrical resistivity of contact material for human protection from lightning

The context of the question is camping and sleeping outdoors in the unprotected elements. If you’re sleeping in a tent close to the ground, and lightning directly strikes your tent or the vicinity ...
0
votes
1answer
38 views

Is the Delay in Strain Data Due to Capacitance?

I have designed a sensor board which gives a strain o/p based on wheatstone bridge principle(change in stress is measured through change in resistance). But the starting value is not at zero level,it ...
4
votes
6answers
1k views

Over 10,000 amps?

Is it possible to have a 5 meter wire that has 10,000 amps or more current flowing? I assume this can be done with a step-down transformer and the voltage could be 2V and lower... I assume that most ...
2
votes
3answers
195 views

Input resistance of a transistor circuit

I have a question from the razavi's microelectronics book: I'm puzzled because in the solution provided, the first line states that: "We know that the input resistance Rin = R1||R2||\$r_π\$." ...
3
votes
1answer
80 views

Use water as a conductor for a circuit powered by 1.5v battery

I've tried to create this quite simple circuit. V1: 1.5 v (AA battery) LAMP1: 1.5 v, 0.2 a (E10 incandescent light bulb) "Salt water": 10 ml regular water + 1 g salt When I connect the wires ...
-3
votes
1answer
59 views

Circuit design for variable number of leds [closed]

I am very new to this field and turned onto it by adruino and raspberry pi. So for my next project I am looking to create, I wanna have 6 leds (20mA 3v) in a line. Now depending on my output from ...
2
votes
2answers
48 views

Can I use a higher ohm resistance relay?

I'd like to build the circuit detailed here, which calls for a 12V DC 260Ω resistance relay: Looking at some relays, what consequence would using a 400Ω relay have? Would I be able to use one ...
1
vote
1answer
37 views

Impedance measurements of Nano-Materials using Hioki 3532-50 LCR HiTESTER [closed]

I have been using Hioki 3532-50 LCR HiTESTER (manual) to measure the impedance, Parallel capacitance and phase angel of nano-materials at different temperatures from ambient to 1150 °C. Lately I have ...
5
votes
6answers
825 views

What is the function of the resistor in the below circuit?

What is the function of the resistor R13 in this circuit?
0
votes
2answers
88 views

At what resistance do I not see a voltage drop across a resistor?

If I have a circuit like this and measure the voltage drop across the resistor I get a value, regardless of what resistor I use: However, if I stick a piece of wood in there instead of the resistor ...
0
votes
3answers
83 views

Why are the Resistance/Resistivity Equations Formulated as they are?

The equation for temperature dependence on resistivity: $$ \rho(dT) = \rho(0)(1+\alpha dT) $$ where \$dT\$ is change in temperature from some reference and \$rho\$ is resistivity. This leads to ...
1
vote
1answer
39 views

Interfacing GPIO pins between a uC and RS-485 tranceiver

uC: EM357 datasheet RS-485 IC: sp3078e datasheet Two input pins on the sp3078e need to go high at the same time when I'm sending bytes. I'm using a single output pin on the EM357 to drive both of ...
0
votes
3answers
71 views

Resistance calculation [duplicate]

Are these resistors in parallel? A question is asked to find the equivalent resistance between X1 and X2; to my knowledge, these resistors are like parallel connections. But the choices are given ...
1
vote
2answers
92 views

Find total resistance of this circuit

I want to find the total resistance between A and B. This is a HOTS mcq, which has the following options: A: 45\$\Omega\$ B: 15\$\Omega\$ C: 5\$\Omega\$ D: 22.5\$\Omega\$ A book says that the ...
0
votes
2answers
98 views

Can I use a diode to block current?

I am building a circuit from a 4.2 volt battery and I cannot use resistors to lower the current, and I cannot calculate the load resistance but I want to protect the switch from over current, and ...
-1
votes
1answer
90 views

How to choose the right transistor for a circuit and its associated resistor? [closed]

Please bear with me. It's easier asking you guys opinion than to Google. Especially choosing the right resistor when working with Arduino boards and transistors for relays.
2
votes
5answers
2k views

Is Ohm's Law violating itself?

Consider the following circuit... simulate this circuit – Schematic created using CircuitLab Now suppose the resistor has infinite resistance. Then obviously the current through the ...
2
votes
2answers
93 views

Reducing voltage for solid state relay

I have a solid state relay which wants a 1.25-2.5V "activation" input, but my output from the micro controller is 5V. Is it possible to use a zener diode for this? Or do I need a buck converter? I ...
4
votes
7answers
209 views

Resistance of a semiconductor diode

When we calculate the dynamic resistance \$r=(\frac{dv}{dI})\$, for any n-p junction, how is it different from the normal resistance \$R=\frac VI\$? Does the equation for the voltage drop (The fermi ...
0
votes
1answer
87 views

For a low pass filter, derivephase of the transfer function, Vout/Vin

simulate this circuit – Schematic created using CircuitLab I have calculated the magnitude: \$ ||H(j\omega)|| = \dfrac{1}{\sqrt{1 + {(RC\omega)}^2}} \$
0
votes
5answers
305 views

Does an ATX PSU's PS_ON Signal Require Resistance

As the title suggests; when connecting the PS_On signal directly to ground in order to switch on an ATX PSU, is there a required amount of resistance? - To try to clarify my particular problem; I ...
0
votes
5answers
212 views

What is more accurate definition of Ohm's law?

What is more accurate definition of Ohm's law and resistance? is it $$R=\frac {V}{I}$$ or $$R=\frac{dV}{dI}$$ This is doubt that developed in my mind during a class where professor derived power ...
1
vote
2answers
120 views

inverted photocell (novice question)? [duplicate]

I'm a terribe novice when it comes to electronics and I've got a question: I have a simple circuit including a photocell that regulates current (I hope this terminology is correct). It works as it ...
2
votes
2answers
174 views

Can I use lower gauge wire for short runs of longer high amp circuits?

This question is probably more of a "please explain whatever concept I'm missing." But I'll start with my specific question. I'm building an electric brewery and am using a 5500W 240V (23A) heating ...
0
votes
1answer
159 views

Driving High Power LEDs with this circuit

I've just completed building this circuit (thanks alexan), times 3 for each RGB channel. R1 = 4.7k R2 = 1K R3 = 10K Q1 = BD140 Q2 = BD139 This circuit is used to power 4x20mA RGB LEDs in ...
2
votes
1answer
66 views

Resistor values for LED

I'm reading this datasheet: http://www.jaycar.co.nz/products_uploaded/ZD0012%20-%20AL-50-30RGBC-C-004.pdf The Preferred Value Series Resistor on this page recommends 510/470/470 Ohms for 12VDC which ...
0
votes
2answers
157 views

Why do measurements displayed in multimeter inconsistently vary by factors of 1000 depending on range?

For my science fair project, I am measuring the resistance of a 100 foot piece of 32 gauge Nichrome wire. Using a Innova 3300 digital multimeter, I get the following results for each resistance range ...
1
vote
1answer
112 views

joule heating - transmitting power at higher voltages reduces resistive loss?

electrical engineering hopeful here. Can someone explain with math how transmitting power at higher voltages reduces resistive loss? I know Joule's Law Power is proportional to (I^2)*R lets say ...
2
votes
1answer
95 views

In a non auto-ranging digital multimeter, what do the increasing numbers in the Ohm section represent?

For my science fair project I am measuring the resistance of nichrome wires under different conditions. I am using an Innova 3300 digital multimeter to measure the resistance. Other websites have told ...
3
votes
3answers
226 views

What is the purpose of a voltage divider in a flex sensor?

I've been following this flex-sensor-arduino tutorial on setting up a simple flex sensor with Arduino, and I got confused on this part: The flex sensor changes its resistance when flexed so we can ...
0
votes
1answer
106 views

Do we include the voltage drop across a diode when calculating the current through the diode, taking into account breakdown has occured?

So, am doing this question paper for my electronics, and I stumble across a question that asks me to calculate the current through a diode, with a breakdown voltage of 1.7, an Imax current of 20ma, ...
-1
votes
2answers
106 views

Voltage and resistance problem [closed]

I have an LED that uses 1.5 volts and a current of about 0.25 milliamps. I have a battery that has an EMF of 1.5 volts. Initially I connected the battery to the LED directly thinking that it was the ...
2
votes
8answers
402 views

Understanding Electrical Engineering with Analogies

Understanding concepts with analogies help can be a useful technique and hopefully this will help me better understand electricity and Electrical Engineering better. Lets start with a simple water ...
1
vote
4answers
196 views

Why is the series resistor getting hot in this LED driving circuit?

I am trying to create the circuit below but then the resistor is getting too hot. I think is has something to do with my power source 15V, 8A. My resistor is 51 ohms, 1/4W. Any comment please... ...
0
votes
0answers
77 views

Is it possible to count human with low current?

Please look at this project http://big.dk/#projects-vvv Description says "A single person can activate the beating heart, but joining hands with others will make the heart beat even faster to create ...
0
votes
3answers
195 views

How to measure a resistance very accurately?

How can I measure a resistance very accurately more than a multimeter (ohmmeter)? For our measurement we are using resistances with values such as 300.8974083. But the instrumentation is very old ...
0
votes
2answers
121 views

Series - Parallel Resistor Calculations

Hi, I would be very grateful if anyone could shed some light on the below diagram as I'm trying to calculate the total resistance between A and B in this series parallel configuration. 10 and 20 ...
-1
votes
1answer
84 views

Measuring input resistance to a MOSFET/BJT amplifier

How would one go about measuring the resistance of a Emitter follower in PSPICE?
5
votes
2answers
278 views

What is negative Resistance

I have heard some people talk a bit about negative resistance, but I have never really understood it. What is negative resistance?
3
votes
2answers
96 views

Telegrapher's equations

Something about the derivation of Telegrapher's equation is really bugging me. When deriving the Telgrapher's equations for a transmission line using a model as shown above, why do we only use a ...
-6
votes
3answers
231 views

What is Kirchhoff's voltage law all about?

what is the Kirchhoff voltage law ? isnt it the sum of potential drops as we move along a circuit till the same point should be zero it is simply energy conservation law that when the battery ...
3
votes
3answers
306 views

Simple measurment of resistance with microcontroller

What is a simple way to measure resistance (in this case 0-100 kOhm) using micro-controller (I'm using STM32, it has 12-bit ADC, timer, but no comparator). I want it simple (not too many components) ...
7
votes
1answer
214 views

What mechanism happens inside a resistor for potential drop and constant current?

What process happens inside the resistor just after being connected to a battery? I am trying to get a picture of it. On applying a potential difference, the electric field it generates pushes the ...