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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A question on an AC Current calculation. [on hold]
So I got this question and I'm not sure of my steps so here goes:
If a 120V rms supply is used to charge a 10A DC device at 14V and the efficiency of the system is 70% then how much current is drawn ...
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3answers
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What is the voltage in electrical circuits?
I understand what the voltage is and I realize that the battery makes an electric field due to the accumulation of the charges in the anode and cathode this electric field causes electric potential ...
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2answers
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Is voltage basically the measure of the strength (or density) of an electromagnetic field? And does an increase in voltage increase the amperage?
I have been in the process of fully understanding what is generally accepted as truth by the scientific community regarding voltage, watts, and amperage. Most engineers seem to say to simply use the ...
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Is there a limit on the magnetic field in a Hall generator?
In a Hall generator, charge accumulation on electrodes occurs because there is a generated current, $\bf{J}$, in a magnetic field, $\bf{B}$. This results in charge separation due to a Hall current ...
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2answers
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Magnetic field in Ohm's law
In a linear, stationary, isotropic, homogeneous, only time-dispersive medium one usually writes Ohm's law as:
$$\underline{\mathcal{J}}(\underline{r},\omega)=\sigma(\omega) \underline{\mathcal{E}}(\...
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1answer
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Conceptual question on volume current density and derivation of the continuity equation
The expression for the volume integral of the volume charge density is
$\int_{V} (\nabla \cdot\vec{J}) d\tau = -\frac{d}{dt} \int_{V} \rho d\tau = -\int_{V} (\frac{\partial \rho}{\partial t}) d\tau$...
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Semantics problem with physics definition [closed]
Definition of current: Rate of flow of electron
then, " The electric current is flowing" would be a wrong phrase due to the above definition
if we replace the current in the above phrase with Rate ...
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Does a relationship exist between current, acceleration and charge? [on hold]
I was looking through a study guide question and came across a confusing problem. Here's the setup:
A cross consisting of two wires is first placed in a cartesian coordinate system with the ...
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How to solve this from RC circuit? [closed]
Find the potential difference across 3 ohm resistor and 3 microfarad capacitor in steady state
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Calculating the current & p.d. using only the terminal p.d. and resistance in series and parallel [closed]
I've done the following calculations but I am not sure whether these are correct. So in circuit 1 (C1) , using V=Ir the current in the circuit is V/r = 1.5/2 = 0.75. Thus the current through the lamp ...
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1answer
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What is the EMF in a bar rotating around any point?
The problem of a bar (or rod) of length $l$ rotating around one of its ends in a magnetic field of magnitude $B$ is very well known. The induced emf is $\frac{1}{2}B\omega l^2$, where $\omega$ is the ...
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4answers
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Can Induced current be obtained by only changing the direction of the Magnetic Field?
According to Faraday, a change in magnetic flux induces current in a conductor. Just suppose we take a circular coil, and pass a magnetic field inside it, and keeping changing the direction of ...
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1answer
34 views
How a battery maintains the current in the circuit? [duplicate]
How a battery maintains the current in the citcuit? Iwant to know each and every step of this process mathematically and theoretically also.
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5answers
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Why does a 60W bulb glow brighter than a 100W bulb in a series?
In my physics class I have this problem that shows two lightbulbs, one 60W and one 100W in series, connected to a 120V battery.
The problems are:
Which bulb is brighter? (A: 60W)
Calculate the ...
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8answers
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Electrical Current vs Power in layman's terms?
I am trying to understand electric circuits (ie voltage, current, power, and resistance). For the most part, everything makes perfect sense, but for some reason I do not feel as if I understand the ...
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1answer
33 views
Movement of electrons in a circuit
Electrons move from negative to a positive terminal, but their path seems unusual.
They seem to be taking the longer path to get to the positive terminal, The electrons could have gotten closer to ...
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1answer
20 views
Magnetic Force on a current carrying conductor
Why does a current carrying conductor parallel to the magnetic field not experience a force?
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How to calculate the current generated by a thin film?
I have a thin film with known dimensions and conductivity. If I hook up wires and apply a bias, how can I calculate/estimate the current that I will get? Here is where I'm at:
$$ \mathbf{J}=\sigma \...
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0answers
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Levitating Super Conductor - Quantum Entanglement or Electric Currents? [duplicate]
In this video (https://www.youtube.com/watch?v=zPqEEZa2Gis) the explanation given for levitation of super conductor is simple electric currents creating opposing magnetic field.
In a similar ...
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5answers
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What's the reason behind the current remaining the same after passing by a resistance?
I've been wondering why does this really happen, I mean by intuition if electrons are driven by EMF (ignoring wire's resistance), $n$ coulombs would pass by a point per second, until they encounter ...
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Why doesn't current flow between the wires in a coil?
Didn't find the answer online, maybe because of bad searching. So hope you here can give me an explanation.
In an engine or transformer the coil is tightly wired, but how come the current doesn't ...
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1answer
32 views
Surface current density confusion
From Griffiths' Intro to electrodynamics:
Now I'm confused about 3 things:
1) What is the 'mobile' surface charge density? Isn't the surface current density itself the 'mobile' surface charge ...
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42 views
Uniqueness of the current loop inverse problem
Imagine we have a circular planar current loop where the current contour is infinitely thin. Free parameters of this loop will be: coordinates of the center; current density $I$ and sign; radius of ...
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How to create a hysteresis diagram using the mass of iron filings and current of an electromagnet
My lab report is based on determining the strength of an electromagnetic when changing the current. My method includes raising the current from 0 to 2 and back down from 2 to -2 and calculating how ...
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1answer
21 views
How to explain these observations on the first load, with two loads in series?
Recently I purchased the Snap Circuits Jr. kit and was working through the different projects with my daughter. We decided to connect two loads in series circuit, powered by the battery source. The ...
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1answer
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Ampere's Circuital law proof for closed circular loop
How do we prove the magnetic field for a circular loop is $\frac{\mu_0I}{2r}$ using Ampere's Circuital law
I proved it using Biot-Savart Law but i am getting $\mu_0I/2\pi r$ instead of $\frac{\mu_0I}{...
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How is current in superconductors increased microscopically?
Imagine a superconductive ring with its current being increased by EM induction.
How is current increased microscopically? I see only two possibilities:
...
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0answers
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What is the electrical resistivity of air during breakdown?
There is a well-documented theory for breakdown voltage vs pressure in the form of Paschen's law.
But what is the trend of the electrical resistivity of air as a function of the electric field ...
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0answers
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Proof that true passive linear memristors doesn't exist
This is a sequel to the following (now irrelevent) question: My attempt to implement linear memristor
Assume the "conceptual symmetry" of the fundamental passive circuit elements holds:
Then let's ...
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0answers
33 views
COMSOL magnetic field time dependent [closed]
enter image description here
I need to modelling conductor in Comsol 5.3 by MF physics in Time Dependent study
Conductor model "Single conductor" in "Coil" feature doesn't work in TD study, and ...
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3answers
79 views
Does touching the Live wire makes it neutral?
If I have two 'hot' wires connected to a source and a load, and one of the wire is connected to the ground, this wire is called the 'Neutral'. But what happens if instead of using an additional wire ...
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2answers
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Why doesn't ionized air give you a current shock?
According to Tesla coil, the air gets ionized and why doesn't ionized air give current shock to a person standing in the ionized air?
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0answers
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What is the advantage of a double pole switch over a single pole switch? [migrated]
I know that a double pole switch is used to cut off the current in both live and neutral wire simultaneously, but by using a single pole switch,if you switch off the current through the live wire, the ...
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1answer
27 views
Conservation of bound charge? [closed]
It is intuitively obvious that free charge is conserved in vaccum. But when is bound charge conserved? I tried to find this by formula:
The charge conservation law in microscopic view (Assuming there ...
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2answers
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In superconductivity, does the diameter of the cable affect the current?
In the water tank analogy below, the smaller diameter pipe (B2)
will drain tank A slower than the larger diameter pipe (B1)
We are told that resistance has this same effect on current
the bigger the ...
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1answer
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How do I experimentally measure the resistance from using dielectric grease on battery posts?
The internet gives lots of contradicting advise about greasing or not greasing car battery posts to prevent corrosion. So rather than rely on the internet, I want to perform an experiment so that I ...
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2answers
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Touching single line of AC Power and charge oscillation in body
If a person touches a single line of AC(Only on the live line, and no where else. Say he/she is hanging on the power line using one hand) as shown in the attached image, Do the ions in his/her body ...
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2answers
54 views
Why is the electric potential difference independent of resistance?
According to wikipedia the definition of electric potential difference is as follows:
The difference in electric potential between two points (i.e., voltage) is defined as the work needed per unit ...
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1answer
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Charge accumulation in wire
I came across a question about charge accumulation. It states that if a steady current flows in a wire composed of a copper and iron wire of same area (see fig), will the charge accumulate on the ...
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3answers
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Do magnetic lines of force depict path of moving charges [closed]
What are the magnetic field lines basically depicting in terms of moving charges or charge carrier particles or currents.
What do those circular loops around a straight current carrying wire actually ...
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1answer
34 views
is this the reason why current doesn't flow over a resistance if there is another path without resistance? [duplicate]
Let's suppose that a single battery is connected with a wire, which does not have resistance. Electrons will start to flow , in reality, with a wire with resistance, a potential difference would be ...
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1answer
48 views
Does a battery 'excites' current to flow in a superconductor? [duplicate]
If yes, how is it possible since a closed circuit with no resistance means 0 voltage, how does the electrons flow initially if there's no potential difference? Any simple explanation or analogy would ...
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2answers
116 views
Is my understanding of current correct?Urgent help is needed! [closed]
I had asked this question:No matter the arrangement of resistors in a circuit, a battery will still produce a current as if it were connected to an imaginary combination of the individual resistors ...
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3answers
35 views
How does the initial turn-on transient decay into the steady state in a given circuit?
How does the initial turn-on transient decay into the steady state in a given circuit? For example, in a parallel circuit, how does the voltage over both arms of the parallel circuit equal to that of ...
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2answers
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Hardest circuit diagram
I have provided an example of the type of problem I am having issues with. In the given diagram, the resistances and batteries are identical and the batteries do not have internal resistances(for the ...
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2answers
61 views
How does the current become homogeneous within a circuit?
I have two questions:
In a given circuit with resistances of different values connected in parallel, there is a different build up of electrons when the power source is turned on. Then, how is the ...
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1answer
54 views
Realistic energy output of a battery
An answer from the post "Battery life with hot and cold wires" talks about Peukert's law related to the battery capacity. Now, within the scope of undergrad electromagnetism courses, the following are ...
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2answers
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Compare the time the power sources in these circuits will last
I am trying to conceptualize the time which a battery will last in a given circuit. Below is an example from which I will explain the questions which I am struggling with :
Lets begin by asking this ...
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13answers
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Why doesn't current pass through a resistance if there is another path without resistance?
Why doesn't current pass through a resistance if there is another path without resistance? How does it know there is resistance on that path ?
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1answer
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Circuit Diagram Problem [closed]
I solved a problem in which I was supposed to find the current over the ammeter. The answer is 12 because the total voltage over the circuit is given as 128 V. However, I do not understand why we don'...
