What is Electric current: Definition and 172 Discussions
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.
Hi
For measuring the casimir effect in a experiment, two conducting plates are set up parallel to each other. As far as I know, in all experiments so far there was always a small electric current induced in both plates.
So my question is: Why is this electric current necessary in such an...
given a electrical network (in the picture)
i asked to find all the current in each resistor.
so for the start i found the RT,i got RT=3.5-ohm (i did it with the Y-delta transform).
then i calculate IT and i got IT=2A.
all i know is R1=2A.
but my problem is how to find the others current...
Hello.
I have attached a file containing a detailed question regarding the definition of the electric current. I'll be glad if someone can help me clarify this issue.
Thanks :redface:
Homework Statement
The model for the resistivity of metals can be described differently by adding the scattering term into the electron equation of motion.
mx'' + (2m/t)x' = qE
Where x is a mean quantity.
DC conductivity is found by considering the steady state when E is constant. Show...
Here's my question. On a closed circuit, you have the electrons of the conductor being pushed-pulled around the circuit from the negative end of the battery to the positive end.
So what happens to the electrons when they reach the positive end of the battery?
In order for the electrons to...
Electric current...
Homework Statement
When a steady current passes through a cylindrical conductor , is there an electric field inside the conductor?
Homework Equations
The Attempt at a Solution
How do i approach this...? I mean i know -E.dx = dV in electrostatics...So going by...
I am having difficulty ascertaining the difference between an electrostatic charge present on the surface of a conductor and the flow of an electron current (or holes, if you prefer) along the surface of a conductor with respect to their effects on the electron density of states (and, more...
Hello fellow PFers,
I'm having some trouble visualizing electric fields along an electric current. Assuming that charge flows from high to low potential, and since electric field lines point from high to low potential, does that mean the electric field is always in the direction of the...
Homework Statement
In the circuit below, find
(1) The total current in the circuit
(2) The battery voltage E
(3) The power loss in the 20ohms resistor
Homework Equations
V=IR
The Attempt at a Solution
I=I1+I2
V=30I1 and V=40I2
30I1 = 40I2
or
V-30I1 = V-40I2
I have a question which is driving me nuts. I have, in all probability, got the wrong end of the stick somewhere, and if so I would be really grateful if someone could pinpoint my confusion.
One reads in introductory Physics books that an electric current IS moving electrons.
But I have...
I'm unsure how to know how much current splits into which wire. So, let's say one wire with 10ma splits into two. On one of the wires there are two resistors each with 10k ohm and on the other wire three resistors each with 10k ohm. Does the current just split in two? Does the amount of...
Homework Statement
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The Attempt at a Solution
1) Ummm ... well ...no idea :-p
2) I guess no. Because if a capacitor is connected with battery, work done by batery is QE (EMF) but thermal energy is just QE/2. Rest QE/2energy is stored in capacitor.
3) Same as (2)
4) i =...
Some websites say electrons in a wire are charge carriers.
I need to know: Charge, electric current, are the electrons from the battery chemical reaction or also the delocalized electrons in the wire, all attracted to the positive terminal of the battery?
Thanks
Hello,
Can anyone explain to me what wire guages are? It just says its a measurement of how large a wire is and how much electric current in can safley handle. Can anyone give more insight? Also, if I want to power something that requires 100watts what size of a gauge should i use and why...
Why is the electric current in the opposite direction of the flow of electrons?
One may say: "Oh, because the electric current represents the flow of positive charges"...
Okay, but why don't the theory use the electric current representing the flow of negative charges?
I heard from a...
Homework Statement
See attachment pls.
for a) I really need to know if this is right(well I know its right but it may not be what they want??).
for b) i need some pointers for (ii) and (iii)
very grateful if you would check a) and i) too... thanks to all future helpers
Homework...
A professor of mine was talking about the electric current. He said electric current is not exactly the flow of electrons through a conductor. He said the flow of electrons is low but energy is propagated through the conductor somehow, when a electric current is present.
I always thought the...
Homework Statement
Consider the electric circuit shown in the figure. Assume that V = 10.4 V, R1 = R2 = R3 = R4 = R5 = 3.00 Ohm. What is the electric current flowing through resistor R2? I couldn't upload the figure, but you can find it on my cramster.com post...
The ampere is that constant current which , if maintained in two straight parallel
conductors of infinite length, of negligible
circular cross-section, and placed 1 metre apart in vacuum, would produce between
these conductors a force equal to 2 × 10 ^{–7} Newton per...
In quantum mechanics, particles also behave as waves with complex phases. By the de Broglie hypothesis, we see that
Vp=w/k=E/p
Does have relation Volt with momentum or wavnumber(2Pi/wavelenght) ?
and current with phase velocity ?
Ive posted this a while back but never had a reply,
How does one determine the heat generated from a current? I have found several sources that refer to using "the length of a wire" but how would you calculate it for an aqueous material, or for all intensive purposes a "really large" battery...
Hi, I need some clarification regarding electric current and why charge flows in a conductor when connected to an EMF source.
I was under the impression the EMF source (battery) produced electrons which were 'ejected' into the conductor, these electrons would then flow around the circuit...
I'm confused by the definition of electric current. It is commonly defined as the time rate of change of charge (I=dQ/dt). However, considering a wire with a steady flow of electrons (a constant, non-zero current), wouldn't the number of charges entering a certain section of the wire equal the...
we know that electric current result of motion of electrons through aconductor
and resistance result of electron's collisions with matter's nuclei resulting in heating material
my question is what is the effect of positive electric field of nuclei at the motion of negative electrons ...
Which of the following would be considered a current?
a negative ions flowing in a liquid
b electrons moving in a vacuum
c positive ions flowing in a liquid
d electrons moving in a wire
e ions moving in a vacuum
I presume all of these would be electric currents after reading this...
Homework Statement
Two wires are connected to a conducting sphere of radius 7.75 cm, which is initially uncharged. One wire carries a current of 3.47 μA into the sphere, and another wire carries a current of 1.26 μA out of the sphere. How long does it take to to produce an electric potential...
Suppose we have an electrically insulated box in a room, and the potential difference between the box and the room is given by V_1=V_{Box1}-V_{room}.
Now suppose we inject the box with X amps of current, for t seconds. The new voltage is now given by V_2=V_{Box2}-V_{room}
By how much does the...
Homework Statement
If 3.32 kg of gold is deposited on the negative electrode of an electrolytic cell in a period of 10.98 h, what is the current in the cell in this period?Assume that each gold ion car ries one elementary unit of positive charge.
Homework Equations
i don't know what...
what will be the effect on photoelectric current if the intensity and frequency of incident photons are increased simultaneously. ? Will the current remain almost same? if so , why?
Let's say you have a square plate with a voltage applied across two opposite corners, connected by the hypotenuse.
Presumably, the electric current density distribution throughout the plate would be such that it would follow the path of minimal resistance, i.e. through the hypotenuse.
If...
If electric current is stated in Wikipedia:
"Electric power occurs when the electrical charge is transferred. Power is defined as charge per unit time. The charged particles are usually electrons, but can also be ions."
Does anyone have an example of such currents, the ions then? Would be...
Two long straight wires are suspended vertically the wires are connected in series and a current from a battery is maintained in them. What happens to the wires? What happens if the battery is replaced by an a-c source.
This is a crude schematic of the circuit.
----|i|i----
|...
1)I do understand why current must be same at all points in series as charge is conserved.
BUT, If a current, say 'I' is created in a loop, then why, exactly, do we say that the current in a part or element of the wire is the same, that is, 'I'?? Why is current independent of the length of wire...
Homework Statement
Find the total electric charge of all the electrons in a 50kg sample of water
Homework Equations
a conversion factor
The Attempt at a Solution
I need the atomic # and the atomic mass but it is water. If I had those two i could solve the problem. How do i get...
Okay, I know what current is. It's Q/t. But why should I know what the current is? What makes current so important besides the fact that it's a factor in voltage, power, resistance, etc?
Sorry for the plethora of electricity topics I have created. :-p
I'm trying to clear up my picture of basic electricity and electronics. I've looked at some other posts that ask what is voltage, but have come away with questions in my mind. Here are some thoughts I'm throwing out there in the area of current energy, speed, and force.
I feel there are some...
Okay, I have another question. I understand about protons and electrons I think. When a proton doesn't have enough electrons around it, that's considered a positive charge, correct? And when a proton has too many electrons, that's a negative charge, correct? And like charges repel, and opposite...
Homework Statement
A battery with emf, E, and internal resistance, r, is connected to a variable resistance, R, at points X and Y, as shown above on the left. Varying R changes, both the current I and the terminal voltage Vxy. The quantities I and Vxy are measured for several values of R...
Homework Statement
a) The potential difference in a simple circuit is 13 V and the resistance is 3 . What current I flows in the circuit? Answer in units of A.
(I got I = 4.333 which is correct)
b) How many electrons pass a given point in the circuit in 7 min?
Homework Equations...
We know that the electrical current is scalar. Also we know that a scalar hasn't got a direction but electric current has got a direction. I've confused! Please help me..
Homework Statement
An isolated conducting sphere has a 10 cm radius. One wire carries a current of 1.000 002 0 A into it. Another wire carries a current of 1.000 000 0 A out of it. How long would it take for the sphere to increase in potential by 1200 V?
Homework Equations
n/a
The...
Why doesn't electric current flow in a circuit when a capacitor is fully charged?
I mean there is still the battery making the E field, why is it unable to move the electrons of the wire of the circuit?
Homework Statement
A circular pan of radius b has a plastic bottom and metallic side wall of height h. It is filled with a solution of resistivity p. A metal disk of radius a and height h is placed at the center of the pan. The side and disk are perfect conductors. what's the resistance...
http://img.photobucket.com/albums/v84/Mittpuff/Picture015.jpg
Above is a battery connected through a circuit. We have to find the Total Resistance (R t) by solving in terms of R.
I'm really confused because I'm not sure what's parallel or in series.
Please, help!
Homework Statement
A power station delivers 620kW of power at 12,000 V to a factory through wires with total resistance 3.0 ohms. How much less power is wasted if the electricity is delivered at 50,000V rather than 12,000V?
b]2. Homework Equations [/b]
P=IV=I^2R=V^2/R V=IR
The...
are these different quantum mechanically?
I thought they were the same since probability current density obeys the continuity equation as the electric current density must also.
prob. current density: ~ psi* grad psi - psi grad psi*
electric current density ~ <psi| p |psi>
are they the...
[SOLVED] Electric Current
Homework Statement
"A power plant produces 1000 MW to supply a city 40km away. Current flows from the power plant on a single wire of resistance .050\Omega/km[/tex], through the city, and returns via the ground, assumed to have negligible resistance. At the power...
I am very new to physics. I am searching for a way to boil water to create steam and use that steam to power a turbine and therefore create energy.
I surmize that water can be boiled if enough electric current is passed through it.
My question is how do I determine how much current to pass...