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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 isn't $V_L$ not equal to $i_LR_L$ according to Thevenin's theorem?

According to Thevenin's Theorem $I_L= \frac{V_{th}-V_L}{R_g}$ whereas $I_L$= current through the load. $V_{th}$= The potential difference across the load resistance when the load resistance is ...
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10answers
4k views

What *exactly* is electrical current, voltage, and resistance?

I am taking AP Physics right now (I'm a high school student) and we are learning about circuits, current, resistance, voltage, Ohm's Law, etc. I am looking for exact definitions of what current, ...
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44 views

Current density and electric current

Suppose we have a wire, having different cross sectional area at different points. We know that for same wire we have constant Current density at every point of wire. Thus we can say that if at ...
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1answer
23 views

Direction of magnetic field around a straight current carrying wire

I am currently studying for O Level and I have been learning about electromagnetism for the past year. The topic has never clicked for me because I've never been taught the true relationship between ...
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0answers
30 views

Proper utilization of Ampere’s Law

I am tasked with finding the magnetic field due to a bus bar, which seems to have the exact same set up as Problem 7.62 in the fourth edition of Griffiths' textbook on Electrodynamics. To which I ...
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1answer
13 views

Relationship between concentration and resistance of aqueous solutions

I'm a senior physics/chemistry student working on a practical assignment where I am trying to identify the resistance of CuSO4 in solution (distilled water). I have recorded my data and determined it ...
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2answers
34 views

What happens when very high resistance is connected parallelly with low resistance

$1.$What happens when a resistor of very high resistance (say $10,000 \Omega $) is connected in parallel with a resistor of comparatively lower resistance of about (say $100 \Omega $)? Is the ...
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6answers
220 views

Why is high voltage dangerous?

High $V$ low $A$ electricity is transformed into low $V$ high $A$ through a step down transformer for safer use in homes. But how is it any safer? The wattage is the same for the pre-transformer ...
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0answers
8 views

Does the electric current inside a wire fluctuate when the wire shape is changed while still having it connected to the terminals?

The electric current inside a wire depends on the electric field across the infinitesimal segments that the wire consists of. If we readjust the shape of the wire, i.e. make changes to the conducting ...
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0answers
50 views

What causes the magnetic field around a wire? [duplicate]

According to maxwell’s equations, a magnetic field is caused by a changing electric field, but where is this changing electric field in the context of a current carrying conductor that has an induced ...
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1answer
70 views

Will electricity follow a path of least resistance on a rotating conductor?

I would like to know if electricity will follow a path of least resistance on a rotating conductor. Please reference the drawing below. This is showing a rotating non-conductive disc with a strip of ...
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2answers
32 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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1answer
53 views

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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2answers
36 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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1answer
36 views

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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0answers
8 views

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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0answers
13 views

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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1answer
29 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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0answers
19 views

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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1answer
35 views

How do electrons flow in the circuit?What a dry cell do to them to make them flow?How is energy transferred?

I read on quora that chemical reactions taking place in the dry cell generates electrons which accumulate in negative terminal and when connected by wires they flow to positive terminal . But my ...
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0answers
18 views

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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0answers
12 views

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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0answers
78 views

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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3answers
54 views

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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0answers
28 views

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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1answer
54 views

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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0answers
15 views

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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2answers
59 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
44 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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0answers
85 views

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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0answers
31 views

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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3answers
40 views

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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1answer
35 views

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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0answers
29 views

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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4answers
92 views

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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2answers
31 views

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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1answer
32 views

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
1k views

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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0answers
27 views

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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3answers
37 views

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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10answers
6k views

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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2answers
92 views

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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0answers
35 views

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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0answers
21 views

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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2answers
31 views

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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0answers
26 views

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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2answers
39 views

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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3answers
57 views

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.
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2answers
345 views

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 ...