Questions tagged [electric-current]

A measure of the rate at which electric charge is transported (especially through a circuit), it has units of charge/time.

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Why is it that potential difference decreases in thermistor when temperature of circuit is increased?

Why is it that potential difference decreases in thermistor when temperature of circuit is increased? From my understanding when temperature increases, there are more free electrons ($n$) so according ...
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40 views

What will happen if an ideal current source is connected to a isolated resistance?

I know that ideal current source is a theoretical thing. But when it comes to solve problems we have to consider these scenarios. Now suppose an ideal current source is connected with an isolated ...
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Classical Explanation for Electron-Ion collisions

Classically, electrons collide with other electrons and massive (by comparison), stationary positive ions as they conduct down a wire when an electric field is applied. Is there a good mechanism ...
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37 views

Current law explained

Kirchhoff's Current Law (KCL) is experimentally proven but what exactly happens?. I have made a model by taking the drude model and adding the interactions between the electrons and the reason why ...
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Electric current doubt

How to find out the direction in which the magnetic needle of a magnetic compass aligns itself when kept beside a current carrying conductor?
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Temperature of an annealed palladium wire in air

I'd like to estimate the temperature of a palladium wire that undergoes annealing by electric current in air. A simplified scheme is shown here: My first guess was to apply the Joule-Lenz formula: $...
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65 views

Rapids in a River

Can I expect to have bigger or smaller rapids in a river that has a water level that is higher than average? I am not sure which way this would go. With the lower water, one is closer to the rocks, ...
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1answer
32 views

Applying the definition of electrical resistance to a voltage source

The resistance (R) of an object is defined as the ratio of the voltage across it (V) to the current that flows through it (I), so why can't I claim that the internal resistance of a voltage source is: ...
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Why does a bird not get electrocuted when it is sitting on a high tension electric wire? [duplicate]

Why does a bird not get electrocuted when it is sitting on a high tension electric wire?
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What is meant by alternating current “reversing direction”

What does it mean when people say that alternating current reverses direction? Do they mean that the electricity starts travelling in the opposite direction (away from the houses and towards the power ...
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When is the free charge density zero at the boundary of dielectrics

It is known that across the interface of two different dielectrics, the electric displacement field must satisfy $$(\mathbf{D}_2-\mathbf{D}_1)\cdot\mathbf{\hat{n}}=\sigma$$ where $\sigma$ is free ...
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What's the electric and magnetic field of an infinite long annular wire with constant current density distribution?

Suppose we have an infinite long annular wire, with constant current distribution equal to $J_z=\delta(r-r_0)$. What is the electric field in $r,\phi,z$ directions and the corresponding magnetic field?...
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169 views

Electric current in anisotropic media

I'm trying to model a bulk metal with anisotropic electrical conductivity such as graphite. I want to run a stationary current through the material and I am using the finite volume method to do this. ...
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63 views

Divergence of current density and electric field within a wire

In the following exercise: I concern myself with the validity of my interpretations of (b). Here I am more confident slightly. The divergence of the current density is merely $- d \rho / dt$, so as ...
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Deriving magnitudes for $\mathbf J$ and $\mathbf E$ from the shape of a conductor

In the following exercise: I have no idea how to infer the magnitude of $\mathbf J$ nor $\mathbf E$ given the shape of the wire. The only clear thing to me here is that A, B and C all have different ...
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Formula for total current and phase angle in function of given currents and phase angles in the branches of a parallel RLC circuit

Consider this parallel RLC circuit powered by an sinusoidal alternating voltage and two branches, one containing an ohmic resistance $R_1$ and a capacity $C$, the other one containing an ohmic ...
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Resistance and temperature relationship

When the temperature changes from $\theta_1$ to $\theta_2$, having $\alpha$, and the amount of resistance ($R_1$) in the previous temperature ($\theta_1$), we can calculate $R_2$, the amount of ...
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Can a superconducting wire conduct unlimited current?

A superconducting wire has no electrical resistance and as such it does not heat up when current passes through it. Non-superconducting wires can be damaged by too much current, because they get too ...
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How electric current flows through liquids and gases?

i know in liquids there are electrolysis. But are there time limit in electrolysis ? I think because the ions go and connect slowly to electrodes, and when there are no ions in the liquid, the curent ...
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About device in which potential drops in direction opposite to current

A small intro: We have mainly three types of electronic-devices with their characteristic property: Resistor with Resistance($R$) Capacitor with Inverse of Capacitance($1 \over C$) ...
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How does electricity travel near the speed of light if electrons drift at a snail pace? [duplicate]

I was in a reddit argument with someone who said electrons didn't flow at the speed of light in a circuit. Then he linked the Wikipedia page for drift velocity and defeated me in one fell swoop. Now, ...
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Orientation of resistor when connected in a cicuit [closed]

Consider a cuboid shaped resistor. Now Case1: Connect the resistor along is length to a battery. Case2: Connect the resistor along is breadth to a battery. In the two cases the length and cross-...
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How would this circuit behave? [closed]

A function generator is hooked up to two resistors in series. The voltage across the function generator changes over time, shown by the different graphs The questions ask to find the output voltage ...
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Detection of surface potential change

So if I have a large metal plate with a small electric current in it and the plate makes contact with a small metallic rod. Since the surface of the metal plate slightly changed, will I be able to ...
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In aluminum, how does electricity travel through the surface oxide layer?

Suppose I connect a conductive wire (cross section 1 mm$^2$) to an aluminum object. Since aluminum is highly conductive, electricity will flow smoothly inside the object with little resistance. ...
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60 views

Why does current always go to the resistance which is lower? [duplicate]

Why does current chose the easy way? Is there a proper mathematical formula about why current tends to go over a resistance which is smaller?
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1answer
67 views

How to (hypothetically) calculate $\tau$, the mean free time?

Referring to the Drude Model, I've seen a lot of excellent questions on whether $\tau$ should be thought of as the "average time between collisions" or the "average time until the next collision", and ...
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Relation between electric charge and electric current distributions via velocity

Assume we have a charge $\rho(\vec{r},t)$ and current $\vec{\jmath}(\vec{r},t)$ distributions given in some region of space. From Maxwell's equations we know that the only relation between these two ...
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1answer
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Under which condition the drift velocity stops increasing proportionally with respect to the electric field

Our professor asked us a question the other day but i wasn't able to figure it out. If we increasing Electric field then drift velocity will increase, Because of this Equation: Vd = μ * E But at ...
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Grounding on the wooden floor

Let's suppose that I'm touching a live wire and standing on a wooden floor. Will I be shocked? Or e.g. standing in a plastic tub filled with water. I cannot imagine that there is a closed circle to ...
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What remains the same: voltage, current or resistance? [closed]

A current 1 ampere passed through a conductor which resistance is 10 ohms, if the current become 2 amperes, then will the resistance of the conductor will remain 10 ohms, and if not, then what is the ...
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Moving fluid from one vertex of a triangle to another using windmills/spinners

I want to move fluid from point A to point E. Points B, C, and D are all "windmills" / spinners. Which directions (clockwise, counter-clockwise) should each windmill spin to provide maximum fluid flow?...
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Why alternating current produces electromagnetic waves? [duplicate]

So my question is: why alternating current produces electromagnetic waves? There are plenty of answers on google that state it as fact, but none answer why. I mean what is it about accelerating ...
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Potential in open branch of a parallel circuit with grounding [closed]

If the switch is still open, what will the electric potential at Q be, i.e. negative, positive or zero? Is there a potential difference across the grounded point and point Q, or R3, even though the ...
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How to induce large current in a flexible wire

I have not tested this method in the lab or anything, but based on what I know about electrodynamics I would say the following set up could work: I would take two straight flexible free-of-current ...
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8answers
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Does Ohm's law $V = IR$ mean voltage causes current, or does it just say that voltage and current are related?

I have read that Ohm's law, $V=IR ,$ just means that $V$ is equivalent to $IR ,$ not that voltage is the cause of current. This is similar to the interpretation of Newton's second law, $\mathbf{F} = ...
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Is every open circuit a capacitor?

I think that even open-ended wires can let AC current flow through them, just with a low capacitance. I also think an antenna could be a capacitor and open ended. Am I thinking correctly?
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Flow of charges inside a battery

I am having confusion about the flow of charges inside a battery which is connected to Circuit. Question is, do charges move from one end to another through the battery? If yes, how? Do they move ...
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Would the voltmeters give different readings in a circuit with induced current?

$\def\vE{{\vec{E}}}$ $\def\vD{{\vec{D}}}$ $\def\vB{{\vec{B}}}$ $\def\vJ{{\vec{J}}}$ $\def\vr{{\vec{r}}}$ $\def\vA{{\vec{A}}}$ $\def\vH{{\vec{H}}}$ $\def\ddt{\frac{d}{dt}}$ $\def\rot{\operatorname{rot}}...
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How does back emf occur if a system can’t do work on itself? [closed]

If a coil is connected to a battery and the current starts up, the electrons have to be moving at a certain speed through the wire and therefore have a certain kinetic energy. But if they are moving ...
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Is there Electric Flux through a closed loop around a current wire?

In one of his lectures, Professor Walter Lewin is ammending Ampère's Law to include displacement current (i.e. It not only depends on the current that penetrates the loop, but also on the changing ...
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Why is current-density a vector? [duplicate]

I was told that current has a direction but does not follow vector-laws, so it is a scalar quantity. That's okay. I thought it through Kirchoff's junction law: assume two currents joining at 90 deg, ...
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Empty and fresh battery in series

If you have 2 (e.g. 1.5V) batteries in series and one is dead/empty, what is the reason why a device is not working? Lack of voltage (1.5 + 0 is simply not enough for the device to operate)? From my ...
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Why do we change signs arbitrarily while calculating RC circuits formulas?

When I have to calculate the formulas regarding RC circuits, for example the process of charging a capacitor, there is a discrepancy between my calculations and those of all the books I can find. Let'...
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How does current flow between two adjacent corners of a thin plate when voltage is applied?

If it was an infinite plate then current would have radial symmetry both at A and B. This is a finite plate I'm vehemently against the idea of current having radial symmetry because that will lead ...
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Why does electrical current start to flow?

What happens microscopically when an electrical current starts to flow? I'd like to understand microscopically what happens in detail when electrons start moving (quasi-classically). Electrons can ...
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3answers
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Why is the current same after and before passing through a resistor? [closed]

•Why is the current same after and before passing through the resistor ? •Why is a voltage drop across the resistor ? Explanation in terms of electron flow and electric field will be really helpful. ...
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When the voltage is increased does the speed of electrons increase or does the electron density increase?

I am just a high school student trying to self study, please excuse me if this question sounds silly to you. I know that current is a product of the speed of electrons and the electron density.When ...
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Potential drop in slide wire (Potentiometer Experiment)

While doing the potentiometer experiment I was taught that the galvanometer will show opposite deflection on opposite ends of the slide wire. My questions are as follows: Why does this happen? In ...
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What actually current is? [closed]

Somebody help me visualizing current. What is it actually? Not just with mathematical relations but with something that we can visualize too.