# 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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### Lithium Ion Battery Remaining Life Cycle Prediction [closed]

What are the parameters required for remaining useful life predictions? For example, battery temperature and battery capacity values are helpful for remaining useful life cycle prediction. Other than ...
95 views

### Is current directly or inversely proportional to potential difference? [duplicate]

Ohm's law states that current flowing in a conductor is directly proportional to the potential difference applied across it's ends provided that physical conditions and temperature of the conductor ...
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### Possible value of charges in motion of two charges

Two small particles of charges equal in magnitude and opposite in sign, $q_1$ and $q_2$ have masses $m$ and $2m$ respectively. Initially the distance between the particles is $d$. Both have equal ...
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### What makes of a current in solidstate/semiconductor physics?

If there is some incoming light that has hit electrons of a N-type doped silicon and broke loose these electrons from their covalent bounds and excited them to the conduction band and also excited the ...
121 views

### Why is voltage not affected by wire length even though it is mathematically given as ($V=E\cdot d$), for a wire of length $d$?

If there is $1C$ charge in other side of a battery, the potential being $$V = k\frac{q_1q_2}{r}$$ should change as $r$ changes.
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### Why do we use high resistance wire in potentiometer?

I was recently learning about potentiometer and , my teacher told thta potentiometer wire has very high resistance , but if potentiometer wire has very high resistance , wont the current skip ...
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### Charging a single plate of a capacitor does not work

I charged a 100nF capacitor with 12V with a battery, then i disconnect the battery from the capacitor and connect the positive side of the capacitor to ground (which is an electron source) ...
4k views

### How do electrical devices limit the current flow from a socket?

How does a home appliance limit the amount of current that flows through it? Are there some resistors set up in series in order to cut down the current flow before it actually reaches the device? ...
142 views

### Is potential difference $0$ across a $0$ resistance wire but of non-uniform cross section area?

I know that for a $0 \;\Omega$ wire of uniform cross sectional area, the potential difference across its ends is zero as no electric field is required to move charge with constant velocity (necessary ...
31 views

### What's the magnetic field produced by a current carrying circular loop at a point on its plane?

How do I find the magnetic field in this case? I already know about the magnetic field produced by a current carrying loop at an axial point or center but what about the point on its plane?
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### Laser diode tests - voltage sweep vs current sweep. What's the difference?

I can't wrap my head around it. There's no current without voltage (except eddy currents), and there's no voltage if there's no current, when you pass the current through a diode. So why do people ...
62 views

### How does earthing happen?

Earthing, as I have been told, is done by inserting a conductor in the ground whilst it is connected to the body whose earthing needs to be done. But how does the charge get transferred into the ...
61 views

### Why Faraday's law works with coils?

I always wondering why faraday's law works with coils Faraday's law only works with closed loops An the coil could be open. So the coil here doesn't form a closed loop so that we can apply faraday's ...
95 views

### Why is voltage equal across the resistors connected in parallel? [duplicate]

Say I have a circuit and three resistors connected on parallel. Then if I want to calculate equivalent resistance i use the ohms law(V=IR). Call the three resistors R1,R2,R3 and current passing ...
205 views

### How to generate electric current without a permanent magnet?

The question is pretty simple: Can we build a device that coverts mechanical work in electric current1 without employing a permanent magnet and without access to any external source of current? The ...
10 views

### Is the supply voltage and the induced voltage same in a loaded (practical) transformer?

For a loaded transformer not considering the winding resistances and inductance, induced voltage = Applied/terminal voltage in primary and secondary sides. But given a practical transformer (with ...
2k views

### How does the speed of electricity become the same as the speed of light?

"The field due to the battery sets up a surface charge in the wire. The surface charge is negative near the negative pole of the battery, and positive near the positive terminal, and varies more ...
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### Eddy-current testing

I heard it was possible to detect a flaws in conductive materials using two coils carrying the same current in opposite directions. More precisely, I read it was possible to do so by moving a ...
907 views

### Calculating equivalent resistance [closed]

In the given circuit, find the equivalent resistance between points A and B. I solved this question in two different ways, out of which one gave the correct answer. The correct method is the most ...
115 views

### Is the work done by magnetic field always zero?

In this case the current is flowing in forward direction due to which the force due to magnetic field acts towards the right and the rod moves towards right. Here in this case, I say force causing ...
105 views

### Why Electric field is same in a cross section of wire even if we change its thickness? [closed]

how does E remains same for the increased thickness. E is determined by field lines, if there is fixed number of field lines coming in then how it gets increased by increasing thickness of wire? To ...
41 views

### Why does potential difference cause current?

I'm doing a physics course in my final year of high school, and I'm finding electricity and magnetism conceptually hard. Everywhere online says that potential difference is the difference between ...
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### Why doesn't current flow through an open branch?

I know that current doesn't flow through open branch because current can't flow through air due to its high resistance .But i was thinking , what's the problem if current flows through an open wire (...
48 views

### How does a clamp meter only measure current on the wires inside clamp and not outside?

I think the title says it all, but I'll try to explain better: I know a clamp meter measures current by the current induced (if AC) or the magnetic field created (if DC). But how does the measurement ...
287 views

### If there was zero potential difference between any two points in a circuit would current still flow? [duplicate]

Suppose there is a wire of zero resistance so by ohms law it must have 0 potential difference between any two points, then I connect the wire to a battery which has potential difference across its ...
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### How is electric current possible if no electric field exists inside a conductor?

How is electric current possible if no electric field exists inside a conductor? Since no electric field exists inside a conductor. How is electric current possible as v_d=\frac{(eE)t}{2m},\;\;{E=0}...
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### What is the basic physics of current-electricity? [closed]

Why current decreases when length of resistor increases and How the speed of electricity is almost $c$ (speed of light)?
646 views

### How is light emitted by an incandescent lamp

I am looking for better understanding of how light is produced in an incadescent lamp. More specifically: how is the kinetic energy of electrons converted to light? Are we dealing with interband ...
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### Charge density and free electron density is not the same, right?

Charge density is the density of charges say for example that a piece of copper is charged then the charge density in that piece of copper is the total charge divided by the volume of that piece. ...
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### Why is there no conduction current $i_C$ through a surface between capacitor plates?

The image is from Young and Freedman's University Physics with Modern Physics, Chapter 29 (Electromagnetic Induction). The image shows a parallel plate capacitor being charged where the current ...
163 views

### Why is voltage same for the two resistors connected parallel in circuit?

We know that the electric field inside resistor produced by battery is the actual thing that pushes the electrons in it to move and thus producing some current. We also know that strength of electric ...
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### Reconciling the drift velocity with Joule heating at high and low voltage

I'm trying to reconcile the particle behaviour in an electric field on the micro level with the conductor and the current properties on the macro level. As far I understand - with resistance being ...
26 views

### Is an increase in inductive current caused due to an increase in magnetic field?

I'm studying Inductive current in high school. I learned the Faraday law, and that the voltage produced is equal to the delta of magnetic field flux over time. So, I was curious about this topic and ...
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### Purely resistive AC circuits [closed]

Is it possible to have a purely resistive RC circuit? Recently came across a question: A 130Ω resistor and a 40μF capacitor are connected in series to an AC source of frequency ω. For the combination ...
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### Is power delivered( or work done) by battery completely converted into heat?

I am currently a $9^{th}$ grade student. I recently learned about power delivered by batteries and also the heating effect of current.Consider a circuit consisting of a battery of e.m.f $E$ and a ...
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### Why current in this circuit is zero? [closed]

My attempt:As the galvanometer shows zero current and the portion encircled contains no such device which can store charge therefore current entered must be zero as well. Moving on these lines I can ...
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### How does an electricity meter work? [closed]

I am interested to know how household electricity meters calculate the energy spent in the circuit. The simplest way to calculate the energy spent is to separately measure the current and the voltage ...
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### How Persistent are 0K Superconductor Currents?

Let me build a niobium superconductor ring with a small current and reduce the temperature to absolute zero (1-cm-diameter cylinder wrapped into a 10-cm-diameter loop, carrying 1 mA, with nothing else ...
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### Convert current density from $\mu A/cm^2$ to $pA$

I have an expression that is in Current density of the form $\mu A/cm^2$. How can I convert it to $pA$ - no longer current density, but simply current.
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### Is current (flow of electrons) all about repulsion?

We know that battery produces charge separation between the two terminals by means of some chemical reaction. So now we have negative charge (accumulation of electrons) at negative terminal and ...
31 views

### What is the distance travelled by an electron in a solid conductor between succesive collisions?

Suppose, we know that $\tau$ is the average time between succesive collisions, for finding the displacement, we can multiply $\tau$ with drift velocity, however, is it actually possible to find out ...
113 views

### How to measure the speed of an electric current?

We all know that the definition of a current is the amount of charge flowing per second, that is often expressed by the equation $i=dq/dt$. But is it possible to measure the speed of an electric ...
43 views

### How does the voltage affect current?

The way I see it, volts are ways of measuring the electric potential of an electron in a circuit (I'm assuming from one end of the battery to the other but i could be wrong). So 1 coulomb of charge ...
33 views

### Can a conductor act as a battery?

If a conductor is kept in an external electric field then it develops charge separation and counters the external field. If we connect its opposite ends using a wire and a load then can it act as a ...
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### How electric field changes on changing area of wire?

I know that in an isolated conductor when an external field is applied the charges rearrange themselves end field inside conductor becomes zero. But when this conductor is connected to a battery then ...
14 views

### How do I express the electric field generated in an antenna as a function of the AC current?

If I have an AC current flowing in a dipole antenna (like the one in the picture), how can I write down a function $E(t)$ that depends exclusively on $I(t)=I_0\sin(\omega t)$? Note: the function $E(t)$...
I was given this question and am confused about the dynamics of the system. Consider this problem: a perfectly conductive tube with a radius $a$ and height $h$ is put into a conducting fluid with ...