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 constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship:
I
=
V
R
,
{\displaystyle I={\frac {V}{R}},}
where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current. If the resistance is not constant, the previous equation cannot be called Ohm's law, but it can still be used as a definition of static/DC resistance. Ohm's law is an empirical relation which accurately describes the conductivity of the vast majority of electrically conductive materials over many orders of magnitude of current. However some materials do not obey Ohm's law, these are called non-ohmic.
The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. Ohm explained his experimental results by a slightly more complex equation than the modern form above (see § History below).
In physics, the term Ohm's law is also used to refer to various generalizations of the law; for example the vector form of the law used in electromagnetics and material science:
J
=
σ
E
,
{\displaystyle \mathbf {J} =\sigma \mathbf {E} ,}
where J is the current density at a given location in a resistive material, E is the electric field at that location, and σ (sigma) is a material-dependent parameter called the conductivity. This reformulation of Ohm's law is due to Gustav Kirchhoff.
I'm using a four-probe system (nextron) to measure the voltage between the two points of my sample. Sample has a cylindrical shape and it's placed on its base inside the instrument. The probes are placed on its upper surface (the base of the cylinder).
From the voltage measured, I'd like to...
I know that Ohm's Law gives me the answer of 0.25 A but what I don't understand is how is it ok to use Ohm's Law when I know that the lamp doesn't obey the law? I know that as the current is increased through the lamp, the resistance increases due to temperature rise which, I am told, makes it...
Ohm's law states that current is inversely proportional to resistance, but on the quantum level, why does that actually slow the current down for the whole circuit? In all of the basic explanations, it talks about how the more densely packed matter in the resistor creates more collisions and...
TL;DR Summary: Ohms Law Source Voltage DC series Circuit
Hello,
I'm trying to figure out how to determine source voltage of a DC series circuit. The only information given is
Resistor 1 = 12ohm
Resistor 2 = 9ohm
Resistor 3 = 3ohm
And the voltage drop across R1 is 6V.
The answer is 12V...
I am currently self-learning Ohm’s Law. My current approach is researching Ohm’s law and using multiple sources of information to gather relevant details about Ohm’s Law, like who discovered the laws and what the laws explain, and its concepts, like Voltage and Current.
This approach is making...
I am having problems understanding point (b) so I would like to know if my reasoning in that part is correct and/or how to think about that part because I don't see how to justify the assumption ##v_y=0\ m/s##. Thanks.
I set up the ##xyz## coordinates system in the usual way with ##xy## in the...
Does Ohm’s Law, V = IR work for light bulbs? It appears not to from my simple experiment below.
In the figure below, I measured the resistance of a lightbulb and found that resistance to be 2.6 ohms.
However, when I connect this lightbulb into the circuit where I measure the voltage across...
Hello,
I need help with making sure I am using instrumentation error analysis correctly through an experiment in which I verify Ohm’s Law for a simple circuit. I do have a few questions below. I calculated and measured the error two different ways and did not get the same error by both methods...
Hello. I need help arriving to the answers to the following question above.
You will find the circuit attached
for Number 1 I though that crrent would be maximum when resistance is replaced with a wire but I couldn't get a an expression for ut.
as for question number 2 I tried applying node...
Voltage SI unit = Volts
Current SI unit = Ampere
Resistance SI unit = Ohm
Ohm's law : V=IR
Did Georg Ohm (German), Ampere (French) & Volta (Italian) collaborated when Ohm came out with this electricity equation with units for voltage, current & resistance as per their surnames?
Credit goes to...
This the answer key::
im confused because it say "how much energy has been dissipated after 5s". So shouldn't you be looking at the ground after 5 sec.
but apparently the solution look at it before 5 sec, am I missing anything, can someone explain
Hİ :) as you know potential difference in point A to B is equal to the battery's voltage and point A's current is equal to point B's current.So current is I=Q/t , there should be equal charge passing through at same time so how could there be potential difference when there is equal amount of...
Hello, I wonder if you could give me some advice to how solve this question. What I was thinking to solve it was to determine J by using Ohms law, ## \vec J = \sigma_{\alpha} \vec E ## I already determined the E field for for the sphere, I got it from a) ("a)" was to determined all the bound...
Hi there!
I have resolve this basic circuit, but, i have a little questions about.
The first circuit its:
The diode in all voltaje cases act like a switch, so, the courrent of all components and voltage of the resistance its zero. I graph the curve according my interpretation. My question its...
Hey all. This is about Ohm's Law (and specifically resistance). When you plot the change in current vs the change in voltage you should get a linear trend line (providing it is from an ohmic device). The gradient should be the resistance. My questions is why does the gradient value need to be...
Conceptually I have never really understood Ohm's law, other than using it in calculations. My brain just cannot understand why this equation works.
I was wondering if there is some sort of gravity equivalent to perhaps conceptualise it a bit better.
Voltage: would be the acceleration due to...
This problem is trivial, but I cannot make sense of my answer (I am not even going to bother with the cost calculation.
First, I used P=IV with P=15 MW and V=120 V to find I=125 kA
So far so good. Then I calculated the resistance per meter as R=\rho\ell/A=(1.68\times 10^8\Omega\cdot...
I know there is a serial and parallel circuit
I know R1 = 2k, R3 = 1k and i know Vout which is 1V. And i know 5V is coming from supply. I need to calculate the size of resistor R2.
I can calculate :
1) IR1 = 5-1V/2000ohms = 2mA
2) UR1 = 0,002A*2000ohms=4V voltage drop on R1
How do i go on...
Hi,
I have measured a set of V-I values, and I have to provide the value of the resistance. I have used ac and dc current.
The circuit was quite simple:
power supply -> ammeter -> resistance -> [power supply]
wave generator -> ammeter -> resistance -> [wave generator]
Voltage was measured...
[Moved to homework, so no template]
Summary:: trying to figure out physics for current and having issues. keep getting something that does not make sense.
working on this issue, and i think i have to find ttl resistance, to find current using ohms law. looking at the circuit attached there is...
Hello everyone new here :)
I've recently enrolled myself in a computer technician course and I've encountered a few (basic) electrical sums.
I have absolutely no electrical background, and the course mentioned no requirement of such, but I'm already being presented with work I have no idea of...
Homework Statement
Please help me answer thew question in the image.[/B]
Homework Equations
Current Density J=conductivity X Electric field[/B]
The Attempt at a Solution
As the current density depends on the conductivity of the material through which the electrons constitutuing it are...
Hey guys, I have tried and tried to find a start to this problem with no success. My book may have the answer but unfortunately I must be not realizing it. So hopefully I just need a different perspective. Typically I would find the equivalent resistance of the circuit and then begin to...
If we had a parallel circuit with a voltage of V between the beginning and end, and the circuit has a resistance R, then the current given by ohms law is I = V/R.
What does this mean? The current is not the same throughout the whole circuit. Where is the current equal to this value?
Homework Statement
I am not sure how to calculate the resistance of the circuit and each resistor using voltage and current. I know how to work the resistance out in series and parallel but am 100% how to work it out in combined.
Homework Equations
R=V/I, 1/Rt=1/R1+1/R2
The Attempt at a...
Hi all! Wanted to know if this is along the right lines, or if I'm missing anything... Any help is greatly appreciated :)
1. Homework Statement
Explain the connection between a graph of potential difference versus current, and Ohm’s law.
Homework Equations
slope = rise/run
V=IR
R=V/I
The...
Homework Statement
Homework Equations
No current enters of leaves Opamp Terminals
The Attempt at a Solution
Red line is current path.
Inverting terminal of Opamp -1 is at ground due to virtual ground concept, so Current = 2/1 = 2mA.
This current goes through feedback path and then right...
How is motor speed regulated (lets say a PM DC motor)? Is the voltage kept constant, and current increased/decreased, or is current kept same and voltage increased/decreased or both? What about torque and speed? Will giving a motor too much voltage or current damage it? I'm trying to...
initially my attachment/picture has been cut off that link http://sun.stanford.edu/~sasha/PHYS780/PLASMA_PHYSICS/phys780_2014_l13.pdf page 6
Also I would like to put into words that divergence of current density is accepted as 0 in continuous loop( no capacitors exist...). But if you look at...
Homework Statement
Homework EquationsThe Attempt at a Solution
I believe none of the options are correct .
Option c) would have been correct if E represented peak voltage , I represented peak current and Z is used instead of R .
But I suppose the question is considering E to be E(t) and I...
Homework Statement
Hi,
So I'm just curious whether or not the following statement is correct for the circuit shown. It's part of a bigger problem involving OP-AMPS, the part of the circuit shown is the upper loop connecting from the inverting to the output.
I was just having some doubts in...
I’ve looked at the answers given to the previous times this question has been asked, but I still don’t seem to understand how this holds in the case of a closed circuit. Here’s an explanation given before:
“Think of the wire as a horizontal cylinder. If you apply an electric field pointing to...
I don't understand how this is possible.
This is a rather large transformer in a stereo system amplifier. The transformer is a simple step-down with 120V mains primary to a center-tapped secondary providing both 38V and 76V.
According to ohm's law, at 120V this thing should draw about 85 amps...
Do alternators obey Ohm’s law? The alternator output voltage is proportional to the rotor excitation current. When reducing rotor excitation, the output voltage drops and the load resistance stays constant. Can why still use ohm law to determine the output current.
Example alternator 480 v / 4...
Homework Statement
In Fig. 26-5, how large must R be if the potential drop from A to B is 12 V?
(The figure has been pasted into the attached file).
The answer to this problem is 3.0 ohms. I keep trying to solve this problem but I get a wrong answer. The answer I get from my calculations does...
1. The problem statement, all variables and given/known d
Hi have this problem but I don't know how to represent, however I've tried.
The problem says: You are designing an electric grill and you have to choose a resistance circuit between the circuits shown the figure. Consider that every...
Homework Statement
A potential difference V is connected across a device with resistance R, causing current i through the device. Rank the following variations according to the change in the rate at which electrical energy is converted to thermal energy due to the resistance, greatest change...
Homework Statement
The question reads:
The following graph shows the relationship between voltage V and current I, through a particular electrical component. (The line in graph is straight, not showing properly in the photo)
What is the electrical resistance of this component when the...
Why is the equation Power Loss = I^2*R rather than Power Loss = V*I?
What I mean is why use I/R to represent V?
Also if Power Loss is equivalent to V*R, doesn't step up transformers which creating higher voltage also cause Power Loss to increase which contradicts to textbooks stating that power...
Hello,one thing really confuses me ,in an open circuit the value of resistance is 0 and so due to v=iR the voltage also becomes 0 but my question is how can a current flow in a circuit where there is no voltage Difference? Please help.
Shafia.
I have a 2 AMP regulated DC power supply, with variable voltage 3 - 12 v. If in a small circuit, i.e, small copper wire with 1 ohm resistor. Why am i not getting at max Amps?
I have a question regarding the voltage of two different circuits. In the first circuit there is a 75 volt battery with just one 4 ohm resistor. In a separate second circuit there is a 75 volt battery again, but this time there is a 4 ohm resistor and 9 ohm resistor in series. My question is...
Simple premise: take ohms law with a purely resistive ac circuit. 1 volt through in series with a 2 ohm resistor, I have 0.5 amps of current. I want to maintain constant power. In practice, "how low can I go" with the voltage to increase the current? There's probably many variables I'm missing...
Hello.
Resistive Ohm's law is famously known as V = IR. We can derive its microscopic version as being followed.
V = El, where E and l are, respectively, an electric field and a resistive load length over which a voltage drop V is developed.
I = JS, J and S are a current density and a...
Homework Statement
The following circuit is given.
I intend to calculate the current in every resistor (every quantity except i1, i2, i3, is known).
My textbook states that ℰ3-ℰ1 = (R1+R2+R3+R4+2r)*i, but I think it should be -ℰ3+ℰ1 on the left-hand side, since the current enters the negative...
According to Ohm's law, "Physical conditions remaining the same, the electric current flowing through a conductor is directly proportional to the potential difference across the two ends of the conductor"
I have two conceptual queries:
FIRST
When the ends of the conductor are not connected to...