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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7answers
1k views

How do batteries connected in parallel give more current than batteries connected in series?

Let's say we have three 1V batteries and we're connecting them to a 1Ω resistor. Connected in series, the voltage is 3V and since the resistance is 1Ω, that means that from Ohm's law, the current ...
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4answers
399 views

How does electrical power relate to Ohm's law?

I have some difficulty grasping these concepts. Let's say, for example, a power source of 10W operating at 5V is connected to a load of 0.5 ohms. According to Ohm's law, it is expected that a current ...
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3answers
5k views

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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3answers
622 views

Are \$\frac{1}{4}\$watt 4x\$\Omega\$ Resistor and \$\frac{1}{2}\$watt x\$\Omega\$ Resistor equivalent?

We know Ohm`s law: $$\Omega = \frac{V}{I}$$ $$W=\frac{A}{t} \space\space\space\space\space\space V = \frac{A}{q} \space\space\space\space\space\space I = \frac{q}{t} \space\space\space =>\space\...
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1answer
645 views

Does a semiconductor follow Ohm's law?

Ohm's law is valid for metals, but is it valid for semiconductors? Does it work there? I am not talking about a PN junction here. If I have a block of silicon and pass voltage across it, will I ...
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4answers
348 views

Is Ohm's Law always exactly true even at the microscopic level?

My probability textbook introduction just mentioned that Ohm's Law is not always precisely true at the microscopic level. How is this possible? What is causing this to happen?
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4k views

Calculate expected voltage around a resistor [duplicate]

It's been a few years since I first studied the Ohm's law at school. Now I'm really getting into electronics, and I must admit a part of it still puzzles me. I know this is kind of a strange question,...
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3answers
498 views

Why isn't Ohm's law working for this simple circuit?

I have a 70W 12V-500V DC power converter, and something in these pictures is not adding up. I run the 500V output through a high-voltage 332kΩ resistor. Now, using the left multimeter I ...
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2answers
675 views

Trying to understand why power equation and ohm's law equation aren't agreeing

Hobbyist EE-in-training here. I've been doing some simple problems to reinforce my knowledge of ohm's law and I've run into a snag - A stereo speaker has a resistance of 8.00 Ω. When it is ...
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2answers
298 views

Basic Circuit Analysis using Kirchhoff and Ohm's Laws

So I'm in an introductory circuit analysis class where all we have learned so far are Kirchhoff's and Ohm's Law. I am practicing how to solve these circuits, but for some reason I can't understand ...
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5answers
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Can I use V=IR in the analysis of AC circuits?

My textbooks usually just assert this relation so I don't really know when it doesn't apply. EDIT: Reflecting on this question, I wanted to clarify that I wanted to know if Ohm's Law is valid for ...
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2answers
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Maximum power for Arduino Monster Moto Shield

I'm reading the specs for the SparkFun Monster Moto shield which specifies that Max Voltage is 16V Maximum Current 30A Given Ohm's law, does that mean that the maximum power is 480 watts? That seems ...
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3answers
204 views

How to calculate current on different resistors

I hope this is not a wrong place to ask. I've just started studying electrical engineering and I have (a newbie) question and would really appreciate it if you guys could help me. So I have this ...
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1answer
3k views

why ohmic losses increase with resistance?

Electrical newbie here. I'm trying to get understanding how is resistance involved with power dissipation (ohmic losses, eg. heating). Primarily I'm looking at Electromagnet coil, it says the losses ...
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1answer
3k views

How do I pick the right resistor for an optoisolator given a desired current?

This is a follow up to this question, but isn't specific to the other one. This is both an ohm's law question and a 'how does one interpret data sheets' question. I want to minimize the current I ...
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1answer
311 views

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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1answer
6k views

Design of a nichrome heating element - achieving predetermined power dissipation

I want to make a nichrome heating element with 1500 watts of heat being produced while running on 120v AC. This will be part of a air heater as a fan drives air over a circular coil of nichrome wire. ...
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2answers
784 views

What determines a load's current requirements?

Apologies if this question has been asked before. I'm sure it has but hard to find as wording of question may not bring up the duplicate question. Let us say we have a 10 ohm resistor as a load. ...
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6answers
526 views

What is the voltage potential of ground during a short

During a short, is it possible for the voltage potential of the ground to change? Say for example, we short a 9V battery, how does the ground stay at 0V and not become 9V?
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3answers
542 views

Finding the current flowing in parallel circuit

Lets say we have a circuit with a voltage source and a 5 ohm resistor. The voltage source is 20 v and so the current flowing is 4 amperes (according to ohms law). Now, we add a short wire in parallel ...
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4answers
393 views

Circuits explained without analogies [closed]

So, I am trying to fully understand circuits without the use of analogies like "voltage is like a waterfall" or "a battery is like a pump," since I've heard that those analogies break down when we get ...
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3answers
240 views

Reading datasheets and applying Ohm's Law

I have a CPLD that wants +3.3v and has a maximum allowable current per pin of 8ma. I need to supply a clock signal. The oscillator I selected accepts 5v and outputs 5v-ish levels. I'm finding it ...
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6answers
2k views

General definiton of Ohm's law

There has been some disagreement lately on whether a diode follows Ohm's law or not: Does a diode really follow Ohm's Law? Specifically things like However, the truth is the resistance of a ...
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2answers
3k views

Why doesn't current increases when the voltage is increased

When connecting two batteries in series the voltage is increased. For example: Connecting two 5V batteries in series will produce 10V voltage but the current will be the same. According to Ohm's Law <...
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2answers
750 views

Finding node voltage of a “Y” resistor network

I am trying to find the voltage at NODE1. My initial approach was to find the current starting from the \$15\$V source then going through \$R_1\$ and \$R_3\$ to ground. Then calculating the current ...
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1answer
128 views

Weird Voltage measurement problem

I have a DC/DC converter outputting 5.18 VDC @ 25% load (1 Ohm resistor). If I measure the voltage at the green nodes it fails out of tolerance, if I measure the voltage at the red nodes (before the ...
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2answers
96 views

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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3answers
7k views

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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2answers
389 views

Understanding Ohm and Kirchhoff [closed]

I'm a computer programmer by trade who has taken an interest in Arduino with the hopes of eventually producing a particular hardware project that has captured my hobby/side-business interest. I ...
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3answers
2k views

If the voltage at ground is 0, why is there current flow?

From what I understand, voltage is required to motivate electrons to flow through a circuit. With KVL we have that the voltage will essentially be depleted at the return point (ground). So, if this is ...
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1answer
879 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 ...
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2answers
260 views

LED Blinking after replace

For clear any mistake, the question is: Why the LED started to blink after being replaced? The goal was to replace the blue leds with red leds, after replacing the leds one of them started to blink, ...
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1answer
164 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 ...
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2answers
5k views

A christmas light bulb question

This may look like a homework, but it's not. Actually it is related to Christmas. My Chrismas lights in front of the house are constructed from segments. Each segment consists of 16 incandescent light ...
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3answers
105 views

Finding the voltage of a circuit composed of a series and parallel?

I was watching a youtube tutorial to understand calculations using ohm's law and I thought I had it down when I ran into this problem: I was asked to find the voltage at points A and B. I was also ...
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2answers
11k views

Creating a specific volt/current “test load”

Working on a complex power supply, but to test its limits I would like to create a set of test loads of specific voltage/current. There are several devices for creating a set load, but they seem to ...
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2answers
158 views

How can I find the voltage across R4?

I am trying to find the voltage across R4 in the following circuit: It confuses me that there are 2 voltage sources. I am not sure how to approach it, so I tried this: First, I use Kirchoff's ...
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4answers
171 views

If amps and volts can vary independently, how does Ohm's law actually work?

This is a very basic question as I'm just starting to get into things, but I've hit a roadblock with comprehending the definition of voltage as it relates to the relationship defined in Ohm's law. It ...
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2answers
137 views

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 ...
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1answer
492 views

Simulation measured voltage not matching calculations

Ok, so I have the following circuit: click here for simulation The source voltage is 5V. The voltage measured between A and B is 2.44V, which differs from what I get by calculating that same ...
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1answer
257 views

Understanding current readings from a multimeter

If you couldn't guess, I'm new to electronics. So, I've just received my 3V air pump, it didn't come with any specs, so I'm trying to figure everything out. I hooked it up to a DC variable power ...
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3answers
7k views

Voltage drop measurement result doesn't match my theoretical calculation

I have a \$1.5\Omega\$ resistor and \$8.84V\$ battery. My multimeter tip's resistance is \$0.3\Omega\$. I've tried to compare the calculated voltage drop (which is \$8.84V\$) with the measured value. ...
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1answer
105 views

Induction heater requirements

I am working on determining the specs needed for an induction heater I plan on buying or building. However, I’m having trouble calculating the potential current draw and wattage needed for my ...
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2answers
51 views

Can a power supply be too powerful for a device assuming that the power supply is at operating voltage of the device? [duplicate]

Let’s say a device’s operating voltage is 5V and maximum current that it can draw is 5A. Is it possible for a 5V power supply to have very low internal resistance such that a device that operates at ...
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1answer
2k views

How many watts does tweeter needs

I have a speaker with the following specs: Max. power - 600W Impedance - 4~8 Ohm Freq. response - 45Hz-20KHz Sensitivity - 98dB/W/M The tweeter of the right speaker is not working so i want to ...
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4answers
139 views

How is it possible to have high voltage that is safe?

I am aware that current is very dangerous and only 0.2 amps is enough to stop a heart. However I always see that high voltage is dangerous. Tasers produce a high voltage but since there is low current ...
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2answers
291 views

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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1answer
984 views

Convert transformer resistance data from Watts to Ohm

Short version: How can I convert transformer resistance values from Watts to Ohms? Long version: In PSS/E, transformer resistance can be entered as either per unit values (system base or transformer ...
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1answer
140 views

Understanding Ohm's law(?) for transmission lines

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 ...
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2answers
164 views

Determine supply voltage for led from current limiting resistor

Everyone knows how to calculate the resistance of a current limiting resistor for a LED but is it possible to go the other way? (aka determine the supply voltage from the resistor's value) I ask ...