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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Inductor real charcaterstics when connected to an ac supply
When we connect a dc source to an inductor we always use a resistor there so after solving that RL D.C. circuit we find an exponential function (e to the power R/L based)
But when we are considering A....
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Deceleration with known drag force
so by no means am I a physicist, but I've been working on a problem where I find that I may be very close to the solution...
I'm working on a model roller coaster car that will be slown down by using ...
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What is the magnitude of the current [closed]
A wire carrying a current is shaped in the form of a circular loop of radius $3.0$ mm. If the magnetic field strength at its centre is $1.1$ mT with no external magnetic fields contributing to it, ...
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Application of Kirchhoff's rule [closed]
I came across a problem, in which I was supposed to find the power through the 10-ohm resistor, the one at the top (I forgot to label it). I applied Kirchhoff's loop rule and found the current flowing ...
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Electricity in the atmosphere: effect on human body and on electric components
there are many topics on the web (for instance this, or this famous lecture) about this topic, but I do not understand some basic concepts.
The statement from which I want to start is this (taken ...
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Force due to one half of a current carrying wire on the other [closed]
I have come across a question where i was asked to find out the force due to one half of the above wire on the other (Here, j is the current density). It seems very complicated since i'm not able to ...
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Birds on a wire (again) - how is it that birds feel no current? They are just making a parallel circuit, no?
I have been thinking about this and I know that other people have answered this on here, but there's one part that still baffles me, and it has to do with parallel circuits.
If I connect a battery ...
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How many ampere/current can an electric catfish/electric ray have? [closed]
I know that the voltage of an electric catfish is 300-350 volts, and electric ray varies (ranging from 8 to 220 volts), but what is the ampere of current?
I keep searching every time and it only gives ...
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How to determine the direction of force from a current carrying wire
I'm having trouble determining the directions for magnetic force and field from a current carrying wire.
If I am told that a current is going through a wire directed into the page, is that enough ...
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Joining two insulators at different potentials with a conductor
If two insulators are connected by a conducting wire, will the charges flow if they are different potentials?
According to me, as the charges can't enter the insulators, charges only get distributed ...
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Do resistors heat up with left-over amps?
Apologies in advance if I misunderstand and for my bad explanation.
I have heard that resistors heat up when there are left over amps that are not being used.
If this is the case, why do most home ...
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Back emf in a superconductor
Suppose we apply an ac voltage source to a superconductor.
When the switch is closed we will have a change in electric field across the superconder.
A change in electric field will cause a change ...
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Electric Power ($I=V/R$ vs. $I=P/V$) [closed]
I have a homework question that goes:
"A power station delivers $750$ kW 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 ...
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Are the reference directions of voltage and current associated [closed]
Are the reference directions of voltage and current associated
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Constant current through a conductor is a problem of electrostatics or electrodynamics?
When you connect a constant voltage source across a resistor, there will be a constant current through the wires. Is this a problem of electrostatics or electrodynamics?
If it is a problem of ...
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Is current independent of cross-sectional area?
If I have a conductor whose diameter is nonuniform, why is the current the same across every point of the conductor? I know that I=nqvA, where v is the drift speed, but doesn't that equation show that ...
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What does the resistance of same order means in wheatstone bridge means?
As we know that in order to increase the sensitivity of wheat stone bridge resistance are of same order but here what exactly order means can anyone give me an example of this order?
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Waves and Alternating Current
What will happen if a metallic spring fixed at one end which is connected to a steel wire of certain length and the other end of the steel wire is connected to an AC source. Shall we see the spring ...
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Quantum mechanics: Probability current density in terms of velocity vs. in terms of continuity equation
For simplicity, consider a one-electron system. Some sources tell that the probability current density can be written in terms of the velocity operator $\mathbf{v} = -i[\mathbf{r}, H]$ as
$$ \mathbf{j}...
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How does a current cause a voltage?
In most textbooks I've read, the explanation of Ohm's Law begins by assuming that there is an external voltage applied to a resistive (Ohmic) device. From there, it is explained that this voltage ...
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Physically, what does Force $×$ $d$(Current) measure?
Physically, what does $$\text{Force}\times d(\text{Current})$$ measure?
For example, if we have a boundary of a system and something flowing into the systems through the boundary. Then what is the ...
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Why do electrons stretch when they flow through a wire?
In the question: Special relativity and electromagnetism, the question was in reference to a Veritasium video where he describes how magnetic fields are caused by special relativity. He describes how ...
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Reverse biased semiconductor diode: Name of the current due to which the depletion layer is getting widened?
I know, that in a reversed biased connection the reverse saturation current flowing is negligible but before the depletion layer is widened to its maximum capacity. It seems the current flowing ...
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How do i calculate the magnetic dipole moment of a solenoid?
I would like to calculate the magnetic dipole moment of a solenoid. I have the number of loops, current running through, material type and cross sectional area. Any help would be greatly appreciated. ...
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Can I measure current greater than the full-scale deflection of a galvanometer (works as an ammeter)? [closed]
In the title, I am describing a galvanometer that has been modified to work as an ammeter. The question is stated as follows. Can I measure more current by reducing the shunt (connected in parallel to ...
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Confusion about cells in parallel
I cant understand why cells in parallel will last longer. Could someone please explain?
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Potentiometer comparison of two resistance [closed]
How is the current in both cases in secondary circuit same because we have changed the resistance first it is R then X so current should change.
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Current and voltage - Incompatibility between Ohm's Law and Power Law! [duplicate]
Ohm's Law: I $=\frac{V}{R}$: Increasing voltage increases current.
Power Law: P $={V}*{I}$: Increasing voltage decreases current.
Am I missing something?
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Current in a potential divider [closed]
I dont understand why the current in R wont be the same as that in the 50 ohms resistor. Isnt that the rule for series circuits? The emf for the battery is 18 volts.
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How to find the direction of current in this rotating loop in a magnetic field using right-hand rule for moving charges?
So how can you determine the direction of the current here using just the right-hand rule but without using Lenz's law? The textbook says I should use the right-hand rule applied to the velocity of a ...
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Can a resonance plot be upside down, i.e., inverted?
Given the following RLC circuit with an AC driving source,
$\hskip3in$
I have found an expression for the amplitude to be
$$ I(t) = \left(\frac{V_{0}}{R}\right)\frac{(\omega \tau)}{\sqrt{(\omega\...
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Electric current definition [closed]
I am studying the concept of electric current and I have a doubt about the definition of the current itself that is the following: "the electric current is a net flow of charge through a chosen ...
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Why don't electric current and volumetric flow rate express units/dimensions of area in their denominators?
The definition of current is $I = \frac{dq}{dt}$ and the definition of volumetric flow rate is $Q = \frac{dV}{dt}$.
In written, non-mathematic language, I have seen current described as: "Electric ...
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Boundary Conditions in Magnetostatics - Calculating surface current density
I'm working on a finite element simulation of the magnetostatic magnetic vector potential in 3D, with the following geometry:.
The internal structure is a hollow cored-rectangular current loop. The ...
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Is momentum of electrons conserved when wires form a junction?
Assume constant current flows through the wires. I feel that at the junction, electrons suddenly gain or lose velocity. This is a result of $I=n_e\cdot e\cdot A \cdot v_d$ with $v_d$ (drift velocity) ...
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Current value in Amperes in the moving wire in relation to non moving Ammeter
Let's say if I have a circuit like shown in the picture below. The green wire is not rigidly connected to the black wires, but this green wire can move while maintaining the electrical connection. ...
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Electromagnetic induction - How is the polarity of an uncoiled wire determined? [closed]
Using the right-hand rule, we can determine the solenoid's polarity. So when we move a magnet towards a solenoid devoid of a current, the current flows so as to make the nearest side of the solenoid ...
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What is the microscopic explanation for why is there more power in a circuit with a smaller resistance?
According to the Drude Model of electron flow in a circuit, the drift velocity is inversely proportional to the resistivity.
$$E=\rho J$$
$$E=\rho Nev_d$$
$$E=\frac{-\rho Ne^2E}{m}\tau $$
$$\rho=\...
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Why do hot-wire instruments have a non-linear scale?
Hot-wire instruments are used to measure rms voltage or rms current in AC circuits. The construction of a hot-wire instrument is shown in the following diagram:
Image source: Hitzdrahtmesswerk (Hot ...
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Why do I get a short circuit if I connect the red wire? [closed]
Why the red wire generete a short-circuited with $I_2=0$ and $\Delta V_2=0$?
I have three loops and if I apply the 2nd Kirchhoff's rule, I will have
$$\sum_{\color{red}{\text{2nd loop}}} \Delta V=0$...
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How are electric and magnetic fields able to travel through space and wires, and how are they more than mathematical constructs?
Once I was taught that light is physically made up of in-phase E and B fields oscillating perpendicularly, it was a little baffling because I always thought fields were just analysis tools (or even ...
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Do electrons deccelerate through a resistor?
In a circle the voltage drops across a resistor. This means that some electrons lost some of their electrostatic potential energy. Where does that energy go, and how? For potential energy to be lost ...
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Relation between $V = RI$ and Ohm's law
According to the book Halliday et al., the equation$V = RI$ is not the Ohm's law but simply the resistance definition; the book states this definition applies to all kinds of conductors, ohmic or not.
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How to calculate electric potential of a conductor
I saw a video where an engineer charged a spherical surface of the conductor using a generator, he said that the conductor has an electric potential.
I know that: V = Q/D * K
My question is: how ...
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Magnitude of a current
According to the book Halliday et al., we can define the magnitude of a current as the flow of charge passing through a cross-section of a conductor in the time unit.
The book states also we can ...
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Do metals at low temperature follow Ohm's law?
I think metals at low temperature do not follow Ohm's because of superconductivity. Is it true? What about metals at high temperature?
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In a simple circuit with only cell and wire, where is the electrical energy lost (what causes potential difference)?
Imagine a simple cell circuit with a nine volts cell. Because of the cell, there is a potential difference of 9V between 2 points on the circuit. Because $$Energy at a point = charge * electric ...
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What is the actual physical movement of the electron from the copper atom that produces electric current?
What is the actual physical movement of the electron from the copper atom that produces electric current? Is the electron given a higher energy level and this releases the electron from the copper ...
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Significance of sliding switch in a LR circuit
The following image and statement are from my textbook Concepts of Physics on the chapter "Electromagnetic Induction", topic 38.6 "Growth and decay of current in an LR circuit", sub-topic "Decay of ...
