# 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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### Help verifying Schrodinger's Equations for regions with different potentials

This problem is 1-dimensional along the z-axis. For z<0, V=0. For 0d, the potential is zero once more. I am working under two principles 1)whenever a wave is incident on some discontinuity, some ...
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### How do electrons lose their kinetic energy in ideal wire?

Electrons keep accelerating due to the electric field (produced by the battery) along the circuit. So electrons gain kinetic energy, hence their drift velocity changes. But this is not the case: ...
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### Why voltage is same across parallel resistance?

Since voltage stands for energy per unit charge to be used to carry it from one point to another,why should energy per unit charge be same for two resistors of different resistances,?the energy ...
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### Does a constant current source supply constant current even with voltage changes?

I found that constant current sources have a large internal resistance compared to the load resistance which keeps the current constant despite changes in the load resistance. Will this constant ...
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### A steady line current moving at a steady velocity can produce non-transverse electric fields. What about moving line charges?

A steady, straight current that is stationary can exert a Lorentz force on a moving charge that is parallel to that current. Conversely, a stationary charge can experience a Lorentz force that is "...
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### Electric potential and drift speed of electrons through circuit

What I have since learned: (Tell me If I am wrong) In circuits ,Batteries provide electric potential difference (voltage) ,This difference creates electric field (Over the conductor or the wire) ...
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### Find effective resistance between x and y [on hold]

Find equvalent resistance between x and y
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### Why should the relation (current density)= (resistivity)×(velocity of charge) [$j = ρ v$] be applied to each type of charge carriers separately?

This is from the class 12 physics NCERT Part I. The relation $\mathbf{j} = \rho\mathbf{v}$ should be applied to each type of charge carriers eeparately. In a conducting wire, the total current ...
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### Why does have a shunt resistance in parallel to a galavanometer decrease the amount of current passing through the galvanometer?

The way I understand it is that when you put shunt the current starts flowing more into the shunt resistance than the galvanometer, Then how can galvanometer give a correct value for actual current of ...
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### Torque on a current carrying semicircular coil placed perpendicular to a magnetic field [on hold]

I found out that the force on differential elements will be radially outwards so the net torque about C will be zero but I am confused on how to find the net torque about P. I understand that the ...
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### Electric current and drift velocity

I have seen in several textbooks that say that when we connect a conductor with a battery then electrons start moving (drifting) in the battery in random up and down motion in the opposite direction ...
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### Skin Effect Explanation

I do not understand some things about the Skin Effect. Its Wikipedia definition is: Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
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### Biot - Savart Law and time - variable current [duplicate]

Is the Biot Savart law valid also with currents which are functions of time (for instance a sine wave)?
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### How do resistors generate different heat if we make the current fixed and changed the voltage and resistance? Notice the flow of charge is constant

Consider having a circuit which consists of a battery and one resistor. $V = 10$ volts, $R = 5$ ohms, so $I = 2$ Amperes, and $P = 20$ watts. If we double the voltage and resistance, the current ...
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### Do surfaces charge distribution in a wire move?

Upon reading matter and interactions ,In the chapter "electric field in a circuit" and surface charge distributions in a steady current, The book dosen't explain why doesn't the surface charges move ...
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### Confusion on negative charges, current, and direction

My text book seems to have two contradictory statements about the same subject. Under the electrical potential and capacitance chapter, it says that negative charges move from lower to higher ...
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### If the speed of electron (in space) is increased, will the magnitude of current also increase? [closed]

Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section. (a) ...
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### Which type of conductors don't follow Ohm's law? [closed]

Which type of conductors don't follow Ohm's law? I know that semiconductors and superconductors don't follow them, but why? And what about ideal conductors. What are they? Do they follow ohm's law? ...
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### Would a flow of current (of positrons) zap us?

I have read this question: Will Positron Cause flow of electricity? To your question, yes, positrons are just as good as electrons for carrying a charge. There is no difference between "...
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### Magnetic field generated by a wire crossed by current: clarifications

We know that from Oersted's experience the lines of force of the magnetic field generated by a wire crossed by current $I$, are concentric circumferences of radius $r$ (variable) where the centre is a ...
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### Why does current arrange itself in such a way as to minimize power loss in resistors connected in parallel?

In problem 2 in Problem Set 6, it is said: "Electricity prefers to flow in the way that minimizes energy loss to resistance." Using Lagrange multipliers I was able to show that assuming the above ...
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### Electric current dipole moment

Electrical Current Dipole of dipole moment $\mathbf{p_{EC}}$ has unit of $A\cdot m$. My knowledge of dipole moments unfortunately stopped in high school where I learned that dipole moment $\mathbf{p}$ ...
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### Is Ohm's Law Valid for AC Circuits?

Specifically, let us talk about a circuit containing only an AC source and a capacitor. In this case, the current is 0 at the instant the source voltage is maximum. Same is the case when the circuit ...
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### Magnetic field in a capacitor

If in a flat capacitor, formed by two circular armatures of radius $R$, placed at a distance $d$, where $R$ and $d$ are expressed in metres (m), a variable potential difference is applied to the ...
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### Is Ohm's law valid for water?

I have $E$ (electric field intensity) in water. I want to find $J$ (current density). I don’t know if Ohm's law ($J=\sigma E$) is valid for water. If it is not valid, how do I may find out $J$?
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### Will high voltage but low current glow a bulb?

Suppose I increase the voltage supplied to a building from a constant power source substantially by putting a transformer. Doing this would reduce the current substantially as well. So will the ...
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### All the electric fans in my apartment have started simultaneously producing a high frequency sound. Why?

I woke up last night hearing an odd high pitched noise that I am not used to. I usually keep a few fans running because I have a train that runs nearby and the white noise blocks it out. I tried ...
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### Does the potential difference between two points remain the same if there spatial location is changed?

I was working through this particular homework problem. Where I am required to find out the current flowing through the resistor A (4 ohms). First of all I saw that the 2 resistors were in parallel ...
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### How cell drives electrons to flow in a metal wire?

This was my approach using some facts I'd known- At cathode and anode of a cell reactions take place making positive terminal positively charged and negative terminal negatively charged I.e. there are ...
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### Do $\rho$ and $\vec j$ change in a moving frame?

Consider a cylindrical symmetrical infinite wire with radius $R$. The wire has constant charge density $\rho$ and current density $\vec j$ (pointing to the right). This is measured from the stationary ...
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### Special relativity when observer is traveling with the electrons creating current

There was a situation that has completely baffled me. I<-- -----wire----- q Essentially there are 3 things going on. Positive Charge: Below the wire ...
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### Electric potential due to a current source - Basic equations

In my book I found the folowing formula of the electric potential generated by a current source: $$\Phi = \frac{I}{4 \pi \sigma} \frac{1}{r}$$ where I is the current, $\sigma$ the electrical ...
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### Induced Currents in Circuits

I was given the following question:- The plane figures shown are located in a uniform magnetic field directed away from the reader and diminishing. The direction of current induced in the loops is ...
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### Watts vs. volts amperes

What I understand: In simple DC circuits, this is a product of the current and voltage, such that 1 watt = 1 ampere x 1 volt I understand that a watt is a unit of power (change in energy per unit ...
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### Determining current in a branch having no resistor [closed]

In context to the diagram below , it is quite easy to find the current flowing through section AD , which turns out to be 2A , however , I cannot determine the current in any other branches with ...
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### Can current travel backwards? [closed]

This is not a homework problem. I posted this specific question as it would be easy for me to explain. If a current flows through the wire it encounters a short circuit 1 and after travelling through ...
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### Why can't free electron flow in water to conduct electricity?

This question is related to how batteries work. In a battery, the electrons can only flow in conductors, because they can't flow in the solution. my own thoughts on the matter: I believe it is ...
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### How to show that the electrons responsible for a current have an energy within $k_BT$ of the Fermi energy?

It is commonly written in textbooks that in metals the electrons responsible for an electric current are the ones that have an energy about $E_F$ and a few $k_BT$ around that energy. See for example ...
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### Current when capacitor and resistor placed in parallel?

If the question is too long please comment to shorten it atleast , I really need an answer. I have just started learning about RC circuits and these circuits are confusing me.My questions-1)What will ...
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### What forces are acting on electron in a circuit? Do electrons act on each other in a current?

What forces are acting on electron in a circuit? What is the source of such kind of forces? Do electrons act on each other in electric current? If i have an ordinary electric circuit with only one ...
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### Question about the purpose of a transistor [closed]

I've been studying about diodes and transistors and something made me wonder about the purpose of transistors. In the examples we were talking about increasing current by using two batteries with a ...
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### Connecting one lead of capacitor to a certain charged object (to get a potential difference)

Setup-A charged sphere , connected to one plate of capacitor , other lead of capacitor is free. Question-Will the capacitor plates go through a charge redistribution ? Arguments/Counterarguments-I ...
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### Is a complete circuit required for capacitors to redistribute charges?

Suppose I have two capacitors of different capacitance $C_1$, $C_2$and they have been charged prior connecting by voltage of $V_1$ and $V_2$ respectively the positive plate of one capacitor is ...
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### Physical Relation in Maxwells Equations of quantity between as well as fundamental forces

Recently learnt about Maxwells Equations, am wondering what is the physical relation between electric field E and magnetic field B. It would help if the physical meanings are related to the ...
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### one terminal of battery connected to opposite terminal of identical battery

I have read almost all answers on PSE and ESE but none of them are to the point or maybe I am not understanding.I have described the setup in the title , I just want to know what will happen , will ...
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### Current direction in an electric circuit

in the picture, in the circuit 1, we can see the conventional current direction in the cirucit 2, we can see the real electrons direction it is right i think. but then i have a big problem, during ...
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### How to use energy conservation in following case [duplicate]

A capacitor of capacitance C is intially uncharged is connected with a battery of emf ε.Find the heat dissipated in the circuit during charging?How can we apply energy conservation although there are ...
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### Does current flow in the wire when only one terminal of the battery is earthed?

Let me specify beforehand that this question has been asked previously but I haven't been able to satisfy my curiosity.I know a battery maintains a potential difference between it's terminals , let's ...