# Questions tagged [ohms-law]

A well known relationship that describes the relationship between Voltage and current through a device's resistance expressed mathematically as V= IR. This formula says that voltage across the device is equal to the current through the device multiplied by the resistance.

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### Why would venting an engine create a negative amperage on a generator?

I'm writing simulation software for a civilian helicopter. The helicopter has two engines and two generators. Normally, we calculate the amperage reading of a generator through Ohms. I = W / V. ...
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### Quick Question about ohms law and resistors

This may have been asked before, but I'm currently I'm an argument about whether or not passing 12v through a .1 ohm resistor would result in 120 amps due to Ohm's Law. (I=V/R) Providing that the ...
1k views

### Parallel circuit-find value of resistor [closed]

I have a parallel circuit with 7.5 ohms as total resistance,75 volts, with 2 resistors. R1=10ohms,R2 is unknown. How can I find the value of R2?
2k views

### What would be the effective resistance in this circuit?

How would one go about calculating the resistance between points A and B on the following circuit: This is for Higher Secondary level. The person who needs to solve this understands these basic rules:...
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### Why is the resistance of the circuits input voltage not taken into account when calculating overall resistance of the circuit?

When calculating the resistance in a circuit, one uses Ohm's Law i.e. V = IR with resistors in the circuit. But why is the resistance of the inputs not taken into account? For example, if one has ...
135 views

### Induced voltage of an inductor with a hollow core: can it produce current? [closed]

Hello I'm trying to understand a concept here: if I have a coil wound around a tube, with liquid flowing through the tube, will the electrical flux generated by the coil be enough to perform ...
129 views

### Solving for current through a wire

This is a pretty simple question really and I'll feel embarrassed when I get the solution but its bugging me for now. The goal is to solve for I going from left to right. No values given for any of ...
212 views

### Algorithm for “short-circuit” current draw

Alrighty let's pretend that the circuit contains no resistance other than the battery internal resistance and the wire's resistance itself, Would this be a correct algorithm? (Using OHM'S law) ...
214 views

### Claulating the resistance for the IR Flame Photodiode sensor

Hi I wish to make a IR Flame sensor. I have made a schematic as below. But I could not determine the values for R(x) & Rpot(y). I have tried x = 10K, y=10K , x=1K , y=10K,etc (randomly). But I ...
122 views

### How does Power over Ethernet combine cores to send power over longer distances

Sorry if this is too n00b a question, I'm struggling to wrap my mind around basic EE terms for my project. In my application I run 20 watts over a single AWG-24 wire at 5 volts. This works fine if ...
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### Can a battery produce more amperes as per Ohm's law?

Ohm's law says I = V/R. So let's say I take a 9V battery and attach 1Ω resistance across the terminals. So the current running across will be 9A. But the battery rating says only 500mAh. So are ...
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### Is current/resistance a parabola? (For lack of a better word)

So it occurred to me today that is resistance is the load that draws current, but also the thing that limits it, wouldn't a graph of current to resistance increase, but then decrease?
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### Why lights dim when the AC compressor switches on

If two points in circuit are not connected there is supposed to unlimited resistance between them. So when the compressor is added to circuit it is either very high resistance or very low. In either ...
4k views

### How to calculate the maximum cable length of fire detection loop

I have been tasked with writing a software to calculate the maximum cable length of the fire detection loop, I am not a electrical engineer myself and therefore I am struggling with some of the ...
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### What is kU (V/V)

I have following task I know it's probably really simple (just simple Ohm's law), but I have no clue what kU is. Could anyone explain it to me in the simplest way possible.
827 views

### How to apply Ohm's Law correctly to a circuit?

Ohm's law continually confuses me in my attempts to use it. Right now I'm trying to supply a maximum of 800 mA by 1.5 V from a 5V source. Does that mean that I need a 1.875 Ohm resistor ...
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### led lights resistor

I recently installed an H7 Led Headlight kit 12V/25W in place of a standard halogen 55w bulb. Lights are great, but they flash periodically during can-bus Cold/Warm checks to see if a bulb is out. I ...
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### How did scientists deal with electronics' problems before Kirchhoff and Ohm's laws?

Both physicists developed really powerful laws which still nowadays rule the electronic behavior of circuits. These help us every day to solve problems, calculate circuit variables… but how did ...
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### Volts for power supply, and ohms and watts for the resistor [duplicate]

I'm very new on this for this has never been taught in my school. I have ten 5mm blue LEDs. Each led has 3.4V and 30mA max current. The only thing I know is that I have 34V for my LEDs. The power ...
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### How does an MCU pin detect a voltage?

If I have an MCU pin connected in between 2 resistors (a voltage divider) how does the MCU ...
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### Calculating for current in a single transistor amplifier(almost common collector?)

I was given this circuit for a practice test during one of my classes, but we were never shown how to actually solve it. It's just been bugging me so I wanted to know how others solved for all the ...
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### Why is the calculated current with P=VI and R=V/I not equal?

I'm just starting to learn electronics. I thought I'd start with a simple project of attaching a speaker to a Raspberry Pi (it supplies 3.3V). The speaker I've picked is an 8Ω 0.5W speaker. Now as I ...
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### Sparkfun using 500Ω resistor on circuit with 9V battery and 2V/0.018A LED

A Sparkfun tutorial explaining voltage, current and resistance shows a simple circuit where a LED is powered by a DC source (9V battery). The LED is a red 2V/0.018A LED. The tutorial explains that ...
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### Can anyone explain the ohm's law apply here?

What i am seeking is to explain why the relationship here is not V2/R2 instead it's given as (V1-V2)/R2
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### How is open-circuit voltage calculated?

I'm pretty new to circuits and I only know basic rule from Ohm's law that U=I*R. I quite don't understand how was following formula for Ui created: Why are there only two resistances in numerator? ...
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### Maximum Sound out of a Speaker

I am new to electronics, so please excuse the noob question. I have an 8 ohm 1/4W speaker. I would like to get the loudest sound out of it that I can. Based on my understanding, which may be ...
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### Improve input audio signals to car audio system

I am helping a friend to solve a low and not so clear sound to his car's audiosystem, when using aux-input in particular. He is getting great signals from CD or Radio, but when he feeds the ...
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### Calculating Necessary Resistance In Current Source Circuit

I have a problem where I must calculate the resistance required in R3 to have 1A flowing through the two 9.7V sources in the image below (i.e. Charging the batteries at a rate of 1A). I have ...
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### How can I calculate current(I) when I don't know voltage drop

So everyone knows Ohms law ($I=\frac{V}{R}$) . Let's say I have a 9V battery and a LED. Furthermore the LED only needs 1.9v so the voltage drop of my resistor would be: $9-1.9 = 7.1\mathrm{V}$ ...
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### Ohm's law to calculate voltage [closed]

I know this is a bad idea in practice, I'm more concerned with the theory. How would you use ohm's law to solve this problem. Given V = IR I have a 12v 10amp DC power supply. I want the output ...
568 views

### Simple KVL Problem Not So Simple

We're only a week in to the first EE class here at Uni and I'm already stumped. I can build a power supply in my sleep but anything theory-related turns me upside down. Now, I've done KVL on the ...
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### Thevenin's equivalent exercise

I have this exercise of a Thevenin's equivalent that really got me confused with it's usage of a transistor and was wondering if I could get some help with understanding how to solve this particular ...
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### Simple circuit with transistor using Raspberry Pi

I'm trying to use a Raspberry Pi to control a set of 4 LEDs. I'd like to control the LEDs in software by using a ...
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### Calculate total impedance in RLC circuit with L and C parallel

I am trying to find the total impedance of this circuit but im not getting the right answer. According to my notes the total impedance is 1002 Ω, -86.6°. This is the method i tried: I got Xc = 111....
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### Lithium-ion battery Internal resistance myth

I am making a battery tester, lithium ion battery for particular. and I want to measure the internal resistance, but after testing few cells, I am skeptical for my results, since most of them, new or ...
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### Resistor and voltage of a circuit

I'm a beginner in electronics and I was studying when I had a question, how to calculate the voltage after passing by a resistor. Ex: there is a circuit of 10mA with a 5V voltage, what is the voltage ...
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### Why does voltage split when an additional resistor is added?

When you have one resistor in a series circuit, the amount of voltage taken up by that resistor is 100%. Adding another resistor (same Ohms) makes that voltage drop 50%. Why, since only current should ...
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### How to find the power dissapation of a resistor

I am attempting to repair a circuit (DC-AC inverter) and have incountered a resistor with discolouration. The measurements indicte a resistance of 1.5Mohms or usually OL leading me to belive the ...
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### What damage can 1500V cause to a circuit? [closed]

I'm working on a device that has a supply of 220 V. The output has an LED at the end of a fibre-optic cable coming from the device in question. If, for some reason, a tremendous amount of voltage ...
270 views

### Voltage Divider producing unexpected voltage

I am attempting to create a voltage divider that create 4.5 volts from a 9v battery. Using the voltage divider equation 4.7k / (4.7k + 4.7k) ) * 9v = 4.5v, I ...
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### How to find the current in a complex circuit with nodal voltage sources?

This is circuit. Not sure how to get V, and find current. Any help?
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### Measurement of power dissipation in a resistance

In the above figure (step up transformer), We can calculate $V_s$ using $\frac{V_s}{V_p}=\frac{N_s}{N_p}$ and $V_s=50 V$ So, power dissipated in the resistance, $P=\frac{V_s^2}{R}=2500 W$ (...
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### What is the difference between Ohmic and Non-ohmic devices? [closed]

Besides the fact that one does not following Ohm's law, are there any other differences between these conductors?
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### How do I solve this electrical circuit?

The voltage across R is Vr. I want to plot I vs Vr on a graph. Given I = 6k mA. Now, my question is this: wont I vary with varying V1? Did I copy something wrong, or is there a way to plot this?
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### Switch mode PSU minimum load

Alright, I know I am going to get a lot of flak for this, but let me reassure you that I have already spent the last few days reading on Google while going back and forth from the bench to test ...
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### How to calculate the base-current of this transistor?

Newbie in eelctronics here. How would you calculate the current trought the base of the first transistor? simulate this circuit – Schematic created using CircuitLab follow-up question: What is ...
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### how to determine resistor value calculation for common anode 7-segment display multiplexed

Resistor is required to limit the current flow through the LED since otherwise so much current will pass through that power dissipation shall destroy the LED in less than a second. For nonmultiplexed ...
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### Power calculation and Ohm's Law for Reactance

Hi I have the following question: V = 120V, I = 10 A, I lags V by 60degrees simulate this circuit – Schematic created using CircuitLab The load consists of a resistor and an inductor in ...
I have this easy schematic Next to this is stated that: $$Vb = \frac{Z_{in1}e_{b}}{R_{B}+Z_{in1}}$$ non Latex-version of the formula: Vb = (eb*Zin1)/(Rb+Zin1) I would like to know from where this ...