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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A question on electric current

In my physics book the definition of current is If a charge $∆Q$ crosses an area in time $∆t$, we define the average electric current through the area during this time as $I=\frac{∆Q}{∆t}$. The ...
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How to find Currents based on mesh analysis?

Can anyone explain or give an example as to how to solve these three currents? I have tried very hard, but I keep getting stuck and obtaining the wrong answers.
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How to find Voltage based on reference nodes? [closed]

Here, $V_{ab}$ indicates the voltage referenced from node $b$ to node $a$. In other words, imagine $V_{ab}$ being identified in the diagram as having a "$-$" at node $b$ and a "$+$"...
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Can someone explain, in clear terms (not unmathematical) what short circuit is?

I don't get the idea about what short circuit is. In a few questions I have come across, it appears to be a short circuit but the answers say otherwise. In fact, I don't have a conceptual ...
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What happens when the length of the uniform wire is more than or less than 54 cm?

I understand how to solve this (when $V_{BC}$ is equal to the emf of the second cell then the current through the second cell is zero). However, I'm curious what happens when the length BC is more ...
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Does the attraction between an electron and proton start a circuit or repulsion between two electrons?

Currently learning circuits and our book states that when a battery is placed in the circuit the electrons toward the end of the circuit wire is attracted to the positive terminal of the battery ...
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Average value of a waveform

I was trying to find the average value of waveform but it came out to be negative. The waveform was: $$v(t)=\cases{2t&if $0<x<1$\\-4&if $1<x<2$}.$$ Can the average value of a ...
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Applying Electron Flow Theory to Alternating Current

I am a beginner to electronics, so please excuse my ignorance. I have been searching endlessly for an explanation, but nothing I have read has fully answered my question. Am I correct to say that in ...
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Would we need Alternating Current if superconducting wires existed?

The major advantage of Alternating Current is that it can be transmitted to large distances without significant losses, which is not possible in Direct Current. Had economical superconducting wires ...
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How is there self-induction at the moment of closing the circuit?

I have just learned about self-induction and I'm confused about something. There was a problem where there was a battery connected in parallel with a bulb both connected in parallel with a coil, the ...
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How many currents are there in a circuit?

I've been studying about circuits lately and I have a difficulty when applying Kirchhoff's rules. My question has to do with how can I find how many currents are in a circuit. I know about junctions ...
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What is meant by “plane of the wire”?

In my textbook, it is given that "The magnetic field produced due to current carrying circular wire at its center is perpendicular to the plane of the wire" What is the meaning of "...
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How does the MLX90614 work with two different positive and negative thermopile? [closed]

In an electrical circuit, positive with positive or negative with negative is not possible, but how about this circuit diagram : there's ground (ground usually negative as far as I know) on the left ...
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A Current Electricity Numerical

Q. A cell of unknown emf E and internal resistance r, two unknown resistances R1 and R2 (R2>R1) and a perfect ammeter are given. The current in the circuit is measured in five different situations :...
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Relationship between Electric Fields, Potential Difference and Resistance in Circuits

The battery in a closed circuit creates a uniform electric field in the wire, which pushes the electrons from the negative to the positive terminal. The electrons clearly have more potential to do ...
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I have derived that the impedance of a capacitor varies with time

For a closed electrical circuit comprising only an alternating current generator and a capacitor, I have derived that the ratio voltage/current of a capacitor is not constant. As Wikipedia defines it, ...
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What will be the direction of the induced current in the loop due to the other loop?

Say I have a circular loop in which current is flowing which is being increased as time passes by. And beside it in the same plane there is another circular loop which isn't connected to any circuit. ...
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How to determine the voltage difference using KCL and KVL?

Here is what I have done so far: Using KVL (left loop): -12V = (10+10)*i (i = current) i = 0.6A Using KCL (left loop): Ia(current away from resistor) = Ib(current towards 50 ohm) + Ic(current ...
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How do we find the equivalent resistance in a square circuit with 4 resistors along the diagonals in the square? [closed]

In the given circuit diagram, if the red colored parts indicate a resistor with resistance $R_1$ along $AO$, $R_2$ along $BO$, $R_3$ along $CO$ and $R_4$ along $DO$, is there any method using which we ...
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Are AC circuits limited to only a serial connection?

What would happen if you set a condensator, a resistor and a solenoid all parallel to each other in an AC circuit? Would it not work or is there a way?
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How can more voltage give more power (do more work)?

I * V = W 1A of current @ 1V is: 1W 1A of current @ 10V is: 10W I understand that 1A is 1C-per-second, which is some amount of electrons. Intuitive so far. How can I get more power if I use the same ...
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How is Alternating Current (AC) used in Bipolar Junction Transistor (BJT) without ruining its operation?

In a BJT (Bipolar Junction Transistor), say NPN in common base configuration, we forward bias the Base-Emitter Junction and reverse bias the Base-Collector Junction when using a constant DC supply. ...
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Electricity vs Current [closed]

BACKGROUND: Electromagnetism has been the hardest concept in physics that I do not understand at all back in my old school. Now, I just started studying robotics which requires the basic understanding ...
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Is the direction of current wrong in this circuit? Why? [closed]

I know how to measure the equivalent resistance of this circuit, we say R2, R3 and R4 are in parallel combination and I know the reason of this too. But if we consider the direction of electricity of ...
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Voltmeter and infinite network [duplicate]

An Infinite Network Is Composed Of Identical Batteries And Identical Voltmeters. Reading Of The Leftmost Voltmeter Is V = 15 V And Reading Of A Voltmeter Is 1/n Times Of The Reading Of The Adjacent ...
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Will I get shocked if I touch only the live wire while standing bare feet on the dry floor of my appartment?

In contrary to static electricity the mains electricity must return to the power plant. When I touch the live then the current flows through my body and the floor of my appartment and through soil to ...
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In AC, do Electrons move in perfect Sync with Generator Rotation across the whole distance?

While i'm self studying electricity, one interesting topic seemed counterintuitive to me, which is: When an AC generator connects to a long XX KM length cables; each cycle, the electrons in the cables ...
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What material is superconductor at 394 K and 2 Mega Pascals? [closed]

What material is superconductor (high current) at 394 K and 2 Mega Pascals?
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Calculating equivalent resistance by Wheatstone bridge concept

I've been learning about the concept of Wheatstone bridge in current electricity chapter. I attempted to solve this problem by that concept: I don't know if my method is right. I tried to take the ...
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If the current of the branches in a parallel circuit always add up to the same total, why isn't this true in this example?

Here is a picture: I did some math and got this table: Why doesn't the current add up to the total, since it's supposed to in a parallel circuit? I used Ohm's law to calculate everything. My ...
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Understanding the zero current in a simple circuit

I've simulated the very simple circuit shown below: As you can see, it has two batteries of 1.5 V, and three identical resistors. The electric currents passing through each wire are also indicated. I'...
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If we connect the two terminals of a semiconductor diode with a simple wire, then will the current flow? [duplicate]

We know that inside a semiconductor diode, there is an internal electric field from the N side to the P side. This implies that the N side is at a higher potential than the P side of a semiconductor ...
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Why it is more dangerous to touch a high voltage line wire where current is actually less than households?

I have seen that power is transmitted from power stations to households at high voltage and low current to minimize the power loss. That means the current in the transmission line is less than the ...
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Interchangeable arms in Wheatstone Bridge

I came across this fact recently but cannot seem to make much clarity out of it. With reference to the picture above the condition for balancing the Wheatstone bridge is that B and D should be at the ...
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Electron inertia in alternating current

Alternating current has a small drift velocity which periodically reverses: in other words, electrons move back and forth a small distance. Unless I'm missing something, the electromagnetic force ...
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Are there two groups of charges associated in an alternating current half wave?

Edit: to better express the problem: As alternating current passes along a wire: Individual current charges produce a magnetic field after zig zagging rapidly locally with a small resultant vector. ...
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Current through a junction of two metals

When a current flows through a junction or a contact between two metals of different conductivities a charge is accumulated in the vicinity of contact. The charge accumulated, I've read, is directly ...
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Distance between electrodes and depth of investigation

In geophysics and specifically electrical/resistivity survey methods there is a rule of thumb, which states that the longer is the distance between source electrodes, the deeper is investigation depth....
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Why don't we take $-e$ in equations involving electrons? [closed]

$$dQ = -enAv_ddt$$ is not the given equation but $$dQ = enAv_ddt$$ is where from $Q$ = charge, $n$ = electrons per unit volume, $A$ = area of cross section, $v_d$ = drift velocity and $t$ = time. ...
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What is the meaning of resistance?

I am a 10th grade student and I have a little trouble in knowing what is resistance? I know this might be a silly question for others but My thinking of resistance is that it opposes the flow of ...
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What happens to electrons in a cut wire?

what happens to electrons in a cut wire. I know it is dangerous but out of curiosity if there was a power cable cut and connected to the outlet, the electrons would be dispersed in the air when they ...
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Two formulas for current: how are they the same? [duplicate]

I am struggling to reconcile the two definitions for current density. Definition one: the current is the flux of the current density vectors through a surface: $$I = \iint_{S} \vec{J} \cdot d\vec{S}$$ ...
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Current density in a thin, moving wire

Suppose I have an infinitesimally thin wire (this is of course an abstraction) that moves in space and has a current that changes along the wire (and possibly even in time). The wire is a line in ...
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What is the route the current moves in this circuit? [closed]

What is the route the current takes in this circuit? I can't identify which resistors are in series or in parallel. This is the circuit:
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Which graph shows how the power $P$ dissipated in the load resistor varies with the resistance of the load resistor? [closed]

^ question Which graph shows how the power P dissipated in the load resistor varies with the resistance of the load resistor? The answer is A but what I need help in understanding is why. From what I ...
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Why Ampère’s Law holds for infinite currents?

I'm reading Griffiths proof of Ampère’s Law and in that proof he needs to show that : $$\oint \frac{(x - x^{'})}{\imath ^{3}}\mathbf J \cdot \mathbf {da^{'}} = 0 $$ where $$\imath = \sqrt {(x - x^{'})^...
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On current enclosed by Ameprian loop

Ampère’s law is saying : $$\oint \mathbf{B}\cdot \mathbf{dl} = \mu_{0}I_{inc} $$ Where $$I_{inc} = \int \mathbf J \cdot \mathbf {da} $$ But if my Amperian loop encloses a wire at an angle : What is $...
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How do polarizers really work?

I've been searching for an explanation of how light is polarised, and I came across this short youtube video, which seemed reasonable. From my lecture notes (ICL), I have that: Okay, that's nice, no ...
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Speed of field and data in wire

The speed of field in wire is near the speed of light (speed of field not electron) so why speed of data is in MBPS, I mean why a byte dose not transport with light speed (field speed).

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