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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1answer
30 views

Current in RC circuit

Why is current drawn in an RC circuit (in a circuit powered by DC voltage supply) independent of the capacitor used? While the capacitor is charging current drawn from the battery only depends on ...
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From where do electrons gain kinetic energy through a circuit?

Supposing an ideal wire, How do electrons accelerate and gain kinetic energy? What I understand: When a circuit is opened ,electrons are crowded at the negative term of the battery and have high ...
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19 views

Heating effect on metals

Why does a metal emit photon on heating? Where this photon came from as soon as the metal is heated? What makes the metal to emit photon while heating?
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LCR circuit (AC source) potential difference across capacitor

For a LCR circuit connected to AC source of emf$$E= e\sin(ωt)$$ and let the current in LCR circuit be I then $$I=i*\sin(ωt+Φ)$$ then it is given that potential drop across the capacitor is V.ie$$V=-...
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What is causing the current sinusoidal delay regarding voltage in inductive circuits? [duplicate]

Do electrons acquire some electromagnetic 'mass'as they have so much slow acceleration in the coil due to obviousely electromagnetic field acting on them or it is just the net voltage that drops down ...
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Basic question on Ohm's law

I have what I assume is a very basic question on Ohm's law. Let's say that we have $n$ equal light bulbs in a series with a battery. We know that $$ U - IR - IR - \cdots -IR= U - nIR = 0.$$ Solving ...
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Calculation of eddy currents and subsequent heating in a metal, ATEX-rated junction box

We are building a system which will make use of a stainless steel junction box to connect different circuits within it. This will be located in a hazardous offshore environment so we will be using an ...
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Conventions for direction of current flow and forming a charge difference

I have explored many videos, postings, and lectures regarding the interaction of electricity, magnetism, and motion, including Fleming's Right Hand Rule and Left Hand Rule. While the explanations of ...
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Relation Between Current and velocity of electrons

In a conductor, all the electrons are few to move to conduction bands. If we say that magnitude Current is increased (I= dq/dt) can we infer that the velocity with which the electrons flow also ...
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What causes changes in frequency in the Nation Grid electricity supply? [duplicate]

Following the power cuts in Britain this week, we were told that lack of power being generated led to a drop in the AC frequency as shown in this graph: I understand why a stable frequency is ...
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How to use the definition of volume current density?

The volume current density $ J$ is defined as $ \frac {dI}{da_{\perp}}$ where $dI$ is a small current segment flowing in the volume with cross section $da_{\perp}$ where $da_{\perp}$ is a small area ...
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The currect density in materials of uniform resistivity

Inside an infinitely large piece of material that fills the whole $\mathbb R^3$ space with uniform resistivity $\lambda$ (which letter should I use, when $\rho$ has been used for charge density?), ...
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Constant Current Conundrum [duplicate]

Say we have a simple circuit with three resistors in series, each of which have the same resistance. We also have a battery with a given constant potential difference hooked up in series with these ...
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Current in only inductive AC circuit

Current through a LR circuit is given by $$i=i_0 (1-e^{\frac{-tR}{L}})..1$$From here I can observe that as I tend R towards 0 no current flows through the circuit , and current will be 0 when the ...
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What is the intuitive explanation for high voltage and low current?

By the formula $$P=VI$$ we can say that the voltage can be increased and the current decreased by keeping the power constant. It is mathematically and experimentally right. But is there a way to ...
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Resistors are used to reduce current to prevent light bulbs from “exploding” but it's also said that “current remains same at all points in a circuit”

Resistors are used to reduce current in order to prevent light bulbs and other electrical components from “exploding”, but it is also said that “current remains the same at all points in a series ...
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What does Ohm's law mean in this context?

In this problem Griffiths states that the potential at radius $a$ and angle $\phi$ is $V(a,\phi) = \frac {V_0 \phi}{2 \pi}$ And yes that satisfies the boundary conditions, that at $ \phi = \pi$ , $ V=...
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How exactly does fault current through a person return to the source

this question has been bothering me for a long time Say a person touch the live wire as shown in the picture, the current will flow through him and dissipates into the ground in "rings" as shown in ...
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AC currents for self-inductance of a wire

I've been currently reading some stuff on self-inductance of a wire. There are different regimes where different approximations are used. For the AC currents the notes state that an approximation can ...
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Is electric current reference frame dependent?

$$EMF=\frac{dW_{external}}{dq}$$ $$dW_{ext}=\vec{F}_{net}.d\vec{s}$$ $$\vec{F}_{net}=\vec{F}_{inertial}+\vec{F}_{non-inertial}$$ $$dW_{inertial}+dW_{non-inertial}=dW_{external}$$ After reading the ...
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Is there a way to express the curl of the electric field in the integral form?

In order to experimentally measure the curl of the electric field from faraday's law... is there a way to equate the curl of the electric field to some integral that are measurable in a practical ...
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Deriving Current density of a Moving Point Charge Using the Continuity-Equation

Problem: We know, a point charge at position $\mathbf{r}_q$ has the charge density $$\rho_q(\mathbf{r})=q\delta(\mathbf{r}-\mathbf{r}_q) \tag{2}$$ if it moves with the velocity $\mathbf{v}$, we get ...
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Strange electromagnetic phenomena

Well, I have some doubts about two electromagnetic phenomena that may be related so I wanted to ask you if you could explain them to me. The first one happend some days ago: I was about to go to bed,...
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Why does current remain constant in a series circuit although the rate at which they flow deceases due to the collisions they go through? [duplicate]

I am really confused and frustrated as I can't figure this out. If someone could clear my doubt, I'd be really thankful. According to my textbook current is the rate of flow of charge, it is ...
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What is $v(t)$ in a sliding conducting rail in a magnetic field?

This is problem 7.7c from David J. Griffiths - Introduction to Electrodynamics. A metal bar of mass $m$ slides frictionlessly on two parallel conducting rails a distance $l$ apart. A resistor $R$ ...
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What is the direction of force acting on a current carrying conductor? [closed]

Let magnetic field be from left to right side of the screen and current be flowing from top to bottom part of the screen. Then the force acting on the conductor is out of the screen (towards the ...
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Conservation & Flow of Energy in Circuits

Before I ask my question, it's important that you know how I understand the underlying physics of circuits, so you could point out any misunderstandings or incomplete thoughts. A battery creates an ...
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Potentiometer's working

I know that in a closed circuit with multiple batteries, current is provided by the battery which has the maximum voltage. Let's suppose that $E \gt V$. Now, the voltage $V_b$ at point $b$ will ...
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Charge in a conductor

How to measure net charge flowing through a current-carrying conductor or a wire without actually measuring the current?
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1answer
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Conflicting models about how energy transferred in an electric circuit [duplicate]

I've been studying DC circuits recently, but I've run into some confusion concerning how batteries deliver energy to circuit elements. From what I've read online, it seems that energy in circuits ...
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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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1answer
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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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2answers
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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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63 views

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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5answers
125 views

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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1answer
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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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1answer
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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 ...