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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Verilog-A Current/Voltage/Power Inconsistency

I'm simulating a phase change material in Verilog-A and need to calculate the power across the material. The material is a resistor, so it satisfies Ohm's Law. Therefore, P = IV = (I^2)R = (V^2)/R ...
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1answer
132 views

Do I understand Ohm's law correctly?

I was reading a bachelor's thesis and it mentioned some technical details of a heated plate. Part of the technical details: MK2b Dual Power Technical Details [7] ...  Power Input: 12V or ...
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1answer
641 views

What can cause a resistor to become non-ohmic?

Can anyone help me find some causes as to why a resistor may become non-ohmic? Thanks in advance.
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1k views

What is the Danger in Plugging an 4 Ohm Speaker into an 8 Ohm Amplifier?

I know it is a commonplace warning not to plug in a 4 ohm speaker to an amplifier rated for 8 ohms. I am wondering what is the actual danger that is presented by doing this in an electrical sense. ...
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1answer
21 views

Power up a motor/pump

I have a pump (6-12V 4-5W) that i want to power up with a generator (9V 1.5A). I've calculate the current needed with : I = 5W/8V = 0.55A. Next i've calculated the resistance needed : R = 9V / 0.55A =...
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3answers
4k views

Max Voltage for Speaker of Given Power Rating

I have been looking into the design of loudspeaker drivers and would like to know how to determine the maximum voltage which can be delivered to a given speaker. From Ohm's law we know that P = V^2 / ...
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1answer
1k 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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1answer
67 views

What is the current flowing through the resistor in this circuit?

I have to find the current flowing through the resistor connecting node a to d. I know it's a current divider problem, but I'm having a hard time finding the correct expression. I presume R5 is ...
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7answers
5k views

Ohm's law doesn't seem to be working for this electric motor

I'm a beginner in this field so please forgive me if I'm confusing with my question. There is a component that I can't understand with Ohm's law which is a washing machine drain pump. Washing machine ...
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6answers
264 views

Smallest possible resistance (highest current) [duplicate]

I'm new to electronics and I've been familiarizing myself with some basic formulas, specifically Ohm's law. It seems to imply that if resistance is smaller than 1, let's say 0.00001 Ohm, then I can ...
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1answer
65 views

What’s wrong with my resistance calculations?

I was trying to use ohms law, and there is something I don’t understand. There is a blender that uses 240v at 0.25 A. 240 / 0.25 = 960 ohms However, when I tested the appliance with a multimetre, it ...
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6answers
344 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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4answers
86 views

High voltage, low current and vice versa

Can someone please explain to me in simple terms how is it possible to have high voltage and low current and low voltage and high current and what actually does harm to human body. Here is what I don'...
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4answers
123 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
94 views

resistance and current [closed]

I struggle to understand how if I increase the resistance in a circuit, it requires less current, based of ohms law.
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4answers
243 views

What is voltage exactly? [duplicate]

First, let me start off by saying that I have read the answers to this question (which is the same as mine), but the answers basically explain the different ways voltage is created or compare it to ...
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4answers
1k views

Why are voltage and current directly proportional? [closed]

So, I thought I had an understanding of Ohm's law, but after thinking deeply about it, the direct proportionality between voltage and current doesn't make a lot of intuitive sense to me. So, when I ...
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3answers
189 views

Is it possible voltage without current and opposite [closed]

I got really surprised by seeing this possibilities from a power, energy calibrator is it really injecting it by violating the laws what we use in practice? See the photos? If anyone knows it please ...
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5answers
260 views

Beginner Question about the logic behind Ohm's Law?

In all the physics i learned and practiced many subjects But understanding Ohm's law used to be a big problem for me... Here is what i mean : We have a 5 volt battery. And a 3 volt/ 20 mA led. So ...
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18answers
23k views

How do I prove to my physics teacher that adding a battery in parallel doesn't double the current?

simulate this circuit – Schematic created using CircuitLab My physics teacher said that the current through the resistor is 4A because each battery has a current of 2A if hooked up to the ...
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3answers
826 views

With parallel termination of a transmission line, why does the receiver see the full voltage?

With parallel termination of a transmission line, the line characteristic impedance \$Z0\$ is matched with the pull-down resistance \$Rt\$. But, in that case, shouldn't the receiver see half of the ...
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4answers
359 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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1answer
262 views

UJT Negative Resistance and Ohm's Law

A Unijunction Transistor has a negative resistance region where voltage drops with an increase in current. This was explained to me as a situation where "Ohm's Law is broken". This doesn't sit well ...
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3answers
256 views

Resistance in Ohm's law

Hello everybody I have a question about resistance in Ohm's law, according to the formula "I = U/R" the less resistance you have, the more current you got and accordingly the more power you drain. So ...
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2answers
3k views

How a DC motor works when connected to a power supply but no resistor?

I connected a 12V DC motor to a battery of 12V only. The motor rotated perfectly fine. But my question is that if you don't have a resistor attached to the circuit, as per theory the current is ...
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3answers
2k views

Amps / current doesnt add up to the expected figure - Ohm's law failure on my part!

Can anyone offer suggestions as to where I am going wrong please? In my circuit (diagram below) the system voltage is 12.03 V and the lamp resistance is 2.9 ohms (measured with power disconnected ...
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1answer
52 views

Creating a small range, small baseline varying resistor

I am doing a design project on making a passive varying resistor device. I have a flex sensor that increases in resistance when you bend it. It has a 10k ohm nominal resistance and increase to 110k ...
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2answers
157 views

Finding the value of a specific resistor

Let say you have a network of resistors. All resistors have values but one of them is labeled "R" Given the value of a total voltage and a total current, find the value of R. My head start would be ...
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1answer
73 views

Power adapter giving a specified current [duplicate]

I often see power adapters indicating 5V 900mA (or) 5V 1000mA or sometimes 5V 3.4 A. Obviously they are converting current coming from 220V/110V source to 5V DC using some step down converter. But how ...
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5answers
168 views

Ohms law and voltage

So Ohm's law says I=V/R pretty simple, say I had a 5 volt source and a load I wanted to limit to 20 mA, so I would use a 250 ohm resistor which would limit the current to 20 mA at 5 volts. (I'm ...
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1answer
57 views

Wattage of DC device is not equal to AC [closed]

I have a led driver (LPC-20-700) that is 30V and 700mA, which makes it 21W. I run 10 leds (≈ 2.8V drop) in series with it and it is an constant current device. If I plug my multimeter between, I do ...
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3answers
1k views

Why is my circuit's current far lower than expected with 2.6v / 220Ohm / and LED?

I have a very simple circuit which I have measured the current to be only 3mA but should be in the range of 18mA. I have a simple circuit using 2 AA batteries (NiMH) at 1.3V each in series for a total ...
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4answers
619 views

led resistor calculation, and resistor wattage?

I know this has been asked time and time again but bear with me as I am struggling to understand, so say I have this simple circuit here with 120v (dc for simplicity) as the input voltage and I have ...
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6answers
2k views

How do resistors limit current for an LED? [closed]

If I have an LED with Vf = 2.1V and I = 20mA, Ohm's Law says I should have a resistor in series at a value of R = 145Ω, if the voltage supply is Vs = 5V. However, I believe can put a higher valued ...
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2answers
163 views

Calculating resistance when ohm law has no response

I have a 3v DC source and a 3v light emitted diode, i want power this led with just 5 mA . There is a formula : R = V/I But in my case V is 0 V[source] - V[LED] = 0 So R is 0 always!!! How can i ...
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2answers
1k views

Does resistance of carbon brushes in DC Motors decreases after couple of uses?

I know that after couple of uses DC Motors we should replace carbon brush because the physical size of carbon brush will be reduced and it can not do its job! But let me ask my 3 main questions.... ...
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1answer
114 views

Add a LED and a resistor to a working circuit

We found, with my 6 y.o. kid, a 9V battery and an old CPU fan power supply fan, and we were happy to see the following circuit 1. working. Then he asked: "Can we add a switch and a LED?" For sure we ...
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2answers
86 views

How do voltages at outputs drop as current increases?

As I looked at some 74xxTxx ICs, such as this simple NAND gate, I noticed that the minimum \$V_{OH}\$ decrease as current flowing from the outputs increase. But, from my understanding of Ohm's law, \$...
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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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12answers
11k views

Does a diode really follow Ohm's Law?

Does a diode really follow Ohm's Law? Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the ...
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1answer
59 views

Is my wire rated at a high enough current?

I am in the process of planning a speaker build. I am making sure my current wiring is up to the demands of a new system. The amplifier is a CV 1800, which can put out 9.5 amps at 4 ohms in stereo (...
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2answers
2k 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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0answers
96 views

Solving a circuit with node voltage method

I have the following circuit: Knowns: Iz = 80 mA R1 = 100 Ohms R2 = 150 Ohms R3 = 220 Ohms R4 = 330 Ohms R5 = 100 Ohms As I understand Gi stand for the current source internal conductivity, but ...
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1answer
8k views

Joule–Lenz Law.. Forgotten history? [closed]

We are all, or should be, extremely familiar with this graphic. It is course the magic triangle used to represent Ohm's Law. We should all also be very familiar with the similar power triangle. ...
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3answers
2k views

Do I need a resistor between my battery and servo?

I'm trying to better understand Ohm's law as it relates to general microelectronics projects by taking a simple project I'm working on now. I have a 9V battery powering a small tower pro sg90 servo. ...
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3answers
183 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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7answers
9k views

How can 4 resistors of 30ohms each be connected so you end up with a resistance of 18ohms?

An association of 4 resistors of 30ohms each, how can one assemble them so you get a resistance equivalent of 18ohms?
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1answer
79 views

Using Nodal Analysis Method

Question: I had solved easier circuits problem using nodal analysis but this one it has supernodes on nodes 2 and 3 which I find it difficult solving. thus I need help as I am trying my very best to ...
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1answer
143 views

Why the resistors needs higher Ampers if the Total current is 4 Ampers?

I have a question about the circuit as shown up. My question is if the total current is 4 Amperes, why do the resistors need a higher current? Am I missing something? If that so, what it is?
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3answers
1k 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 ...