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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Alpha particle moving faster than the speed of light

In this problem I was solving a beam of uniform cross section carrying a current of $0.25\ \mu A$ by alpha particles. The mass of an alpha particle is $m_\alpha=4m_p$, where $m_p$ is the mass of a ...
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Does the current inside a capacitor with dielectric becomes zero, if a DC (constant)voltage is applied?

Imagine a capacitor with dielectric with conductivity $\sigma$ and constant voltage source with voltage applied say $V$ is applied to it's ends, now using Ohm's Law we have $ \vec{J} = \sigma \vec{E}$....
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Current without potential difference, in the given circuit?

In the given circuit, the value of current comes out to be 0.5 A Now if I calculate potential difference between point A and B i.e. $$V_B + 3i-1.5=V_A$$ On putting value of $i=0.5A$ we get, $$V_A-V_B=...
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Why is current density in a conductor of uniform cross sectional area constant at all points?

According to what I was taught, if current was dispersed “uniformly,” current density would remain constant. So, in a conductor, the 'current density should be the same at all points.' But, given that ...
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Ammeter readings of variable resistor

Question The diagram in question has no numerical values. $R_1$ is a resistor of constant resistance. $R_2$ is a variable resistor set to minimal resistance. $V$ is an ideal voltmeter. $A_1$ & $...
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Do electric fences such as those typically used to fence cattle generate magnetic fields?

I'm using magnetometers near electric fences and I'm wondering if the electric fence should be detectable and if so, how close do I need to be to the fence for there to be a "measurable" ...
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Why is current same even if the area of the conductor differs?

Current is directly proportional to area if area of conductor increase Current increases but in tapering conductor area increases current remains same I have learned this equation I=enAv Where A is ...
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Instantaneous current and average current

Imagine a simple electrical circuit with a battery and resistor. We know that the average current in any part of this circuit remains same . My question is : is the instantaneous current also same ...
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Why charges does not move through the conductor here if potential at both ends of wire is same?

Two conducting solid spheres are kept apart, one with charge Q1 and radius R1 and the other with charge Q2 and radius R2. Q1=5Q2 and R1=5R2 When these spheres are connected by a conducting wire, the ...
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Current through an ampere loop [closed]

I am trying to apply Ampere's law to find a magnetic field in coaxial cylinders. The inner cylinder with radius $2a$ and outer cylinder is $4a$. Current flows along positive $z$ for inner cylinder and ...
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Molten metal flow due to high currents

It is mentioned in the book "Ampere-Neumann Electrodynamics of Metals", Peter Graneau, that Carl Hering in 1923 operated furnaces by passing high currents through the molten metal pool. He ...
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Current in primary circuit when diode in secondary circuit is reverse biased

Let's say we have an ideal transformer with a diode in the secondary circuit: If the diode is reverse biased, there would be no current in the secondary circuit, which would mean that there is no ...
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How can it be justified that the phase difference between voltage and current for inductor is $\pi/2?$

The inductor is an ideal one, the phase difference is with respect to current, and the voltage varies by the law $V=V_Lsin(\omega t).$ One can prove that the current function will come out to be $I=...
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Would a grounded copper heat sink located near a room's ceiling be an effective way to reduce a room's temperature?

I am thinking about a cheap but effective way to reduce the temperature of my bedroom in my apartment during hot summer nights. I live in an old apartment building and the air conditioner located in ...
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SR for Moving Electrons in Wire

Let's say we have a metal conducting wire with delocalized electrons and positive metal ions. We apply a potential difference across it. Now, the electrons will start flowing in one direction due to ...
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How is there current if there's no voltage?

Hi, I was trying to solve this problem, it asks to find the reading of ammeter. I think it has no resistance here. Does it mean that there's no potential difference, no voltage across ammeter? But how ...
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At which point is the magnetic field in a current carrying loop the strongest?

At which point inside a circular current carrying loop the strongest? Some sources say it is at the centre and some say it is at the circumference. And how can we mathematically prove this? And also, ...
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How to understand the model of electric current and potential in circuits?

According to what I have learnt, there is always a potential difference across a resistor in a circuit (having a battery). Considering a simple 'resistor' circuit, when we apply an e.m.f in the ...
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If one of the parallels of a parallel combination of resistors is broken, how will it affect the other parallels?

All these bulbs have equal resistance and the equivalent current is 6A. I want to know what will happen if bulb 3 is fused. All the sources I have came across say that the bulb 1 and bulb 2 will glow ...
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Is it possible to convert static electricity into current electricity?

Generally, static electricity is created by friction between two or more different materials and it doesn't flow through a circuit. On the other hand, current electricity is the flow of electrons ...
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Does speed of electrons decreases when they pass through resistance?

What type of energy does battery supply to electrons , as I read battery increases KE of electrons but in load if they lose it then speed will decrease and current will decrease after coming out of ...
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How does current flow when two charged spheres are connected by a wire?

Here, the blue sphere (positively charged with +Q charge) is at a lower potential and the pink sphere (positively charged with +Q charge) is at a higher potential, even though they are equally ...
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Relativity and current carrying wire: Do electrons, in their proper frame, distance from each other when they accelerate?

We know that, in the lab frame, a wire can be electrical neutral (having a zero charge density everywhere) both while carrying current and while not. This means that in both cases the linear electron ...
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Current flowing from lower to higher potential

In the above circuit, two cells are connected in series to an external resistance $R$. Now the current going from point $A$ must return back to point $B$ of the cell. But for that it has to pass ...
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Combination of cells with internal resistance

Here are given two batteries $E_1,E_2$ with internal resistance $r_1$ and $r_2$ respectively. To find the potential difference between $A$ and $B$ which is $V_{AB}$, here is what is commonly done in ...
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Why isnt the angle between EMF and LC impedance 90 degrees in AC circuit?

I have a generic LC circuit where the inductor and capacitor are in series and we have alternating EMF. I'm trying to find the the impedance of the circuit with phasors. A phasor diagram shows ...
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Can we make electron drift velocity faster than light by reducing area of resistor?

We know that $I= nqAV_d$. Can we send high current ($I$) through a "fat wire" (more $A$) then reduce $A$ at the resistor so much that $V_d$ becomes faster than light in order to maintain $I$?...
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How does an increase in drift velocity increase the temperature of a conductor?

I have some intuition on how temperature affect drift velocity, but what about the other way around? In a fixed circuit, drift velocity is proportional to current, and current to temperature. In the ...
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What happens inside a conducting wire if it is placed in an electric field?

what happens when you place a long Finite conducting wire in an Electric Field , does current flow through it ? Is Potential Same all over the wire ? i just got these questions in my mind as i was ...
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Why Does an Electric Field Arise In This Situation?

Suppose you have a battery, and using some wire you connect the positive terminal of the battery to some conductive piece of metal (i.e. an electrode) and similarly you connect the negative terminal ...
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$V$-$I$ characteristics and circuits [closed]

The only solution stuck in my head goes through finding the resistance from the slope of the curves and using it somehow in the solution, however, I can't figure out what voltage do I use for X and Y? ...
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Voltage and series circuit [duplicate]

Suppose I have 2 series circuit. One will have resistance $R_1$ and the other $R_2$. Now my question is why is voltage difference same across both resistor? The top part of both resistors should have ...
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Fluctuative current and voltage graph shown by LabQuest 2

I was in physics class and was tasked to measure current and voltage of a circuit using LabQuest 2. The circuit was connected to a battery, which means it's a DC circuit. But when I use the LabQuest ...
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2 answers
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Is the speed of signal transport via electricity as fast as light? [duplicate]

Let us assume a time synchronization system that comprises a sender and a receiver. The sender generates and sends an encoded signal which presents the current time to the receiver periodically, and ...
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8 votes
10 answers
866 views

Why is Power = Voltage $\times$ Current?

So P = I*V because V is the amount of energy per coulomb and I is the amount of electrons going past a cross sectional area in one second. So if we do the math, since V = J/C and I = C/sec, if we ...
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Does the magnitude of the induced current change?

The coil is circular and is closed, meaning that current can flow through it. So this enters a region of magnetic field where with time, more and more magnetic field lines cross it. My question is, ...
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What happens to the electric field lines in a high resistance conductor?

When a conductor is connected to a potential difference, an electric field occurs inside the conductor. We know in a high resistance conductor (for example a 20m long thin carbon rod connected to a 1....
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1 answer
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Do multiple current flows exists in a conductor? Does a slower current provide extra resistance?

If you have a running marathon with lots of people the slower people are in a sense an obstacle for the faster people behind them. The slower people create extra resistance. Is there an analogous ...
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2 answers
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When a loop A induces a current in an adjacent loop B does the change in current in the loop B affect the current in loop A?

Let's say we take a Loop A connected to an AC voltage source and place it adjacent to a closed Loop B. we know that the change in the current in Loop A leads to a change in the magnetic flux through ...
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Question regarding power consumption by a device running on electricity

Say I have a device with resistance $R_2$, connected through a wire of resistance $R_1$ to a source providing potential difference $V$. If I close the circuit then current $I$ will flow through, and ...
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How is Lorentz Force $BQv=BIl$?

The formula for Lorentz Force on moving charge is $$F=BQv$$ which for current carrying wire is modified to $$F=BQv$$$$=BQ\frac lt$$$$=BIl$$ Where $l$ is the length of the wire inside the magnetic ...
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2 answers
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Solenoid emits electromagnetic radiation, why? [closed]

A sinusoidal electric current is applied to the solenoid. The solenoid emits electromagnetic radiation, why?
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What kind of electric field a homogeneously charged full insulating sphere produces outside and inside the sphere?

A homogeneously charged full insulating ball generates an electric field. What kind of electric field is inside the sphere and outside?
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Does the space between field lines inside the conductor increase with distance and eventually disappear?

In practical scenarios where resistance is present, what happens to the electric field lines within a conductor? Practically, we say there is no flow of current in a high resistance conductor with a ...
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1 answer
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Motion of the electrons in a electric conductor when connected to a potential difference?

(I am a beginner in physics, so please forgive me if this is stupid.) Normally, under static electric state there is no resultant electric field existing inside a conducting material. But, when a ...
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1 answer
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Is their an inherent flaw in using a step down transformer for a coil gun

I am currently in my first year of an engineering program so just recently learned about the many wonders of electromagnetism. For a school project this year I went on to build a coil gun using the ...
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1 vote
2 answers
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Does, and if so, why does the frequency of light and wavelength of light affect the photoelectric current?

It makes sense that intensity of light affects the photoelectric current, but what about the frequency and wavelength, given that intensity remains constant? The formula for intensity would be I = nhf/...
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2 votes
1 answer
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What is the relationship between voltage, current, and a transformer?

First off, I just want to say thank you for any help! Also, I ask that if you can, please try your best to explain this to me in layman terms. I understand ohm’s law and I have a decent grasp on ...
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The direction of turn of a coil

I'm confused about how the coil is turned. If the magnet is brought closer to the coil then the first coil at A should become North ( if viewed from magnet's side). But to find direction of current I ...
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3 votes
1 answer
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Why is electric field larger in a resistor?

Suppose there is wire with 0 resistance and a resistor between them and that circuit is plugged to nonzero voltage source. Why is the electric field in resistor larger than of the wire? I want to ...
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