An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In a electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.The SI unit of electric current is the ampere, or amp, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit Electric current is measured using a device called an ammeter.Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conductors, they cause Joule heating, which creates light in incandescent light bulbs. Time-varying currents emit electromagnetic waves, which are used in telecommunications to broadcast information.
How would you unify the two Lagrangians you see in electrodynamics?
Namely the field Lagrangian:
Lem = -1/4 Fμν Fμν - Aμ Jμ
and the particle Lagrangian:
Lp = -m/γ - q Aμ vμ
The latter here gives you the Lorentz force equation.
fμ = q Fμν vν
It seems the terms - q Aμ vμ and - Aμ Jμ account for...
Hello ,
I was looking into current density analysis of a PCB that handles distribution of AC power . from ansys and cadence sites , i realized by current density they refer to DC IR drop that is a pure ohmic analysis that doesn't take into consideration the AC effects . And in order to take this...
Hi! I'm trying to understand electromagnetism. So I had a question: if we place a bar magnets on the low friction surface near vertical wire, then switch on the current, what will happen? As I been told they will align with the magnetic lines, and then nothing will happen. I also suggest that...
I shorted the inductor and performed mesh analysis. The solutions to the linear system were done using a calculator. The book says that the value for i2(0-) should be 15 mA but I'm getting -2mA. What am I doing wrong? I'm completely confused. Maybe mesh isn't the most efficient way to find I2...
Yeah so I'm confused about this circuit because it has an overlapping path. My guess is that the current doesn't flow in one of the two paths in the middle but I don't have a good reason for it (I don't know why). I suppose there is symmetry but I haven't been able to find good videos on...
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...
I have to prove three equations above.
For first two equations, I've been thought and made reasonable answer by using a definition of the electricfield.
However, for third, I can't use a definition of a magnetic field due to the cross product
Like J_2 X J_1 X (r_2 - r_1).
I think three of 'em...
So basically we can have a constant current but i don't understand this circuit.
for example: i can have the Ia what ever I want with current divider rule: Ia = Iq * R2/R3. So Ia is proportional to the ratio of R2/R3.
And if i give a resistor at the collector terminal, if i change it between...
I honestly have such a dumb question- it says “a pitch angle” but cannot find that in relation to a helix. It is not defined in the textbook. Looking on google I found a helix angle, but is that different than the pitch angle? Can anyone draw me a picture of where the pitch angle is?
I assumed...
There is a type of fusion pinch concept where instead of imploding a metallic liner filled with gas fuel mixture they have a chamber with a central electrode and outer electrode , filling the chamber with gas and then a arc discharge is initiated and this discharge drives the gas like a piston...
I am not an educated man, so please try to answer in Layman's terms.
It makes no sense to me. How and Electrical circuit that has X amount of current flowing through it, and X amount of current being used by a Device. I.e. a Washing Machine, Light bulb etc. have the same current flowing out of...
My wife read an article last night about an outbreak of hemorrhagic fever in rabbits, and it has been passing through populations throughout the US. So, I decided to look into it and came across a wildlifehealth.org. There is a lot of nasty stuff out there.
Detection of High Pathogenic Avian...
I did a kvl loop and got V + 5Io - 15 Io = 0
So, V = 10Io
Then, substituted dq/dt for Io and q/c for V
I get to dq/dt - 50000q = 0
solving this equation i get q = C x e^50000q (c for constant)
my Io = dq/dt
so Io now is 50,000Ce^50000q
now my Q(0) is 3 x 10^-5
So my Io (0) should be...
Hi, I have the following question from an old City & Guilds paper:
A resistive load rated at 65 W, 110 V is to be used on a 230 V, 50 Hz supply.
Calculate
(a) current in the load
(b) voltage drop needed across a pure inductor connected in series with the load
(c) inductance of this...
Hi,
I need to calculate the temperature of a wire, due electric current passing through, and I have no idea how to do that. I need it for a device that I want assemble.
I'm using one single thread (strand) of speaker cable, like you can see in this picture:
Again, Just a single thread that...
Many years I read a lay person friendly article on Horava Lifshitz gravity. https://www.scientificamerican.com/article/splitting-time-from-space-evidence/
Im curious to know how has this theory developed? Is it taken seriously? What are the outstanding problems ? Have there been any impressive...
If I want to carry 10 A through an 8 AWG wire, I understand that there will be a specific magnetic field around the wire which will decrease as I move outward from the wire radially. Let's consider the center of that wire as coordinates (x,y)=(0,0). An object located at (0,10) would see a...
Summary:: So the question is, what do I need to do on clamp 'ab', so that the total current only goes through the Inductor L1.
I know the must be a second inductor parallel to the capacitor C1, but i don't know why.
Can someone please explain.
I also included the german question under the picture.
Hello,
I was reflecting on the functioning of a balanced Wheatstone bridge circuit:
Point C and D are at the same electric potential V (zero potential difference). Even if they are connected by an ideal zero resistance wire, current will not split at either node C or D to flow through that...
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I'm trying to model common mode current with LTSpice, but there is a problem with my simulation. Someone else tried on an other software and got the expected result, but I can't explain why. When going through the capacitor, square signals should become pulses, but that's not the case...
Hello!
I've obtained common mode choke from detached pieces, so I don't know anything about them, exept for their inductance/resistance.
I'd like to know how could I determine the rated current of these coilsthank you in advance for your help
In a normal circuit it's easy enough to visualize the path electrons take through a wire. Even considering leakage current in a capacitor, it's easy enough to visualize a large parallel resistance that current "leaks" through. Is there such a way to visualize corona discharge? I get that it...
The resistors are all in series , with exception of R, so I added them together and then used the current divider equation to solve for R, and I got 720 ohms. The textbook says R should be 30 ohms. I’m completely lost.
Hi,
I was trying to read about the current produced by a dynamo in my physics books but I can't find any reference.
I have a rotor rotating at a certain speed, air flow and with a certain inertia, but how can i find the power produced and related current and tension?
I'm an EE with only a surface knowledge of solid state. I know this forum is mostly for students but I don't know where else to find a lot of physicists. Also, please forgive me if this is a dumb question.
For a circuit I want to build, I need a transistor that can conduct > 10,000 A, but does...
To my understanding, current density is simply the current flowing through the alkaline electrolyzer divided by the area (the units for current density are A/m^2). But what would the area be in this situation? Is it the area of the electrodes or maybe the area of the electrolyte solution or...
e=QxV
t=Q/I
p=(QxV)/(Q/I)
=V/I
The expression I came up with for a) is the potential difference divided by current to get power but I have no idea if that is even right if someone could just prompt me in the right direction that would be greatly appreciated
I am not sure if I should use the word 'current' or 'charge' but my question is whether, in a typical U.S. residential 120/240 split phase system, is the local transformer always the source to which current (charge?) must return? Or can it bypass and go direct to other PoCo elements/generators...
I check the datasheet of LM 319 high speed comparator online. I was wondering if LM 319 can accept negative supply voltage(-10V) and its possible to produce a 10V to -10V square wave which oscillates along origin rather than just 10V to 0v as shown below.
I read that "the azimuthal drift is compromized because the typical life expectancy of ring current particles is only hours to days and thus of the same order of magnitude as the drift period". But, if it is so, why relevant current exist? How could we armonize the fact that the azimuthal drift...
Hello!
I'm currently working on a project which aims to study common mode current filters. What I'd like to know is how can I generate enough common mode current in order to be able to make experiment on my filter ( its efficiency to reduce it for example)
I have some constraints:
-the current...
Hi, there. I am interested in quantum gravity. But I am not sure how to find review papers about its recent developments. I tried "quantum gravity" on google scholar. But I could not find a suitable review other than that about loop quantum gravity. I am not sure what are the other approaches to...
Hi all, my work is shown on the attached image. The boxed equation is what I get to but I do not understand how to go from there to what the book has. I am guessing that the problem arises when trying to solve the cross product. I understand that I will need to find the value of the sine of the...
I am trying to understand the current path for corona. Assuming the corona appears on the high voltage electrode, how are the electrons actually flowing? I understand that with flashover a low resistance current path is created as the air is ionized but what is happening with corona?
So for the first question it is very straight forward. The magnetic field is going through the loop, increasing the flux through the loop. The induced current must flow clockwise in order to generate a field that goes through the loop in a downward direction to oppose the change.The second...
Without mathematical formulas, but only with a "Physical intuitive meaning", why if at t=0, I have a charged capacitor, and I connect it through a wire ,forming a closed path, to a inductor the current increasing with time and his derivative decreasing?
To me seems like the inductor oppose "to...
As per ohms law the current is generated based on voltage and resistance V=IR. So if 5v and 1k resistor the current 5mA flows in resistor. But if I take a current source, can I pump any amount of current to resistor? So, current drawn is not characteristic of resistor?
I used the above equation, and started with getting the cross product of dl and r, which was equal to 0.00195i+0.00365k. From there, I divided each component by the magnitude of radius cubed (0.827^3). I then multiplied by I and u naught(u_0=4pi*10^-7), and then divided by 4pi. The answer I got...
I have a graph of mean signal (per pixel) vs exposure time (sec) for 8 different dark frames. I am being asked to find the bias in ADUs/pixel and the dark current in ADUs/sec/pixel and I am very confused on how I could get it. I know that the average of all of the mean signals is a rough guide...
I was following this problem up until they say we can they state I3= I1-I2. I understand why we can say that but I don't see how I can use that to get the system of equation in terms of I1 and I2 at the bottom. Could someone show me how this was done?
The answer from my teacher is two of these photovoltaic cells are connected in parallel. I can understand the parallel connection will produce same e.m.f but I don't understand why the total current will be greater than ##I##.
I imagined one of the cell connected to a lamp. The current through...
I started a project, and where I thought I has a potentiometer position feedback, best I can tell I have an eddy current position sensor, which I'm absolutely not familiar with
The application is a diesel engine injector pump (retrofitting to a different engine, it was from a Komatsu V12, no, I...
Somehow this answer is incorrect , but i realize that even numbers are hipothetical , 45 coulumbs is too much charge , what is wrong in my calculations?
Hello,
I have used an edge current of 10 A through a 0,45 cm (lenght) wire inside an air sphere. The thing is that, according with Ampere law, the magnetic field (B) produced at a 1 mm of distance from the wire shall be 0,002 T, and I am obtaining much higher values in this simulation (around...
Hi,I have found in my textbook the formulas for both current and voltage and I have no idea if they are right or wrong. Can someone help me with these formulas?
v=v0cos(wt)
i=i0cos(wt)
Is this correct? In google when I search for the answers I get something else:
v=v0sin(wt)
i=i0sin(wt)
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...