# 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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### How can I simplify this circuit? And how can I find the Thevenin equivalent for it? [closed]

I am struggling to find a more simplified version of this circuit, which in turn is making it more difficult for me to find the Thevenin equivalent for it as seen through the RL resistor. The line ...
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### What is the area $A$ in the magnetic flux for AC generator and a coil?

I am getting confused with what area do you use in AC generators and coils. Let me explain: in an AC generator, there are two coils that rotate. When using the equation - magnetic flux $= BA\cos(x)$, ...
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### How does having free electrons make something a conductor?

My question is how does having free electrons make something a conductor? I know that the flow or movement of electrons create a current but can't you just add free electrons (such as a battery) to an ...
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### Time Constant of a Capacitor in DC

I've just started studying Physics and I'm not sure how you're supposed to calculate the time constant of a capacitor when a direct current is applied. DC means that frequency equals = so the ...
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### What makes a conductor able to pass electricity?

My question is what makes a conductor able to pass electricity? I know that conductors have free electrons where as insulators don't have as many but can't you just add free electrons to the insulator ...
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### Why, when an electromagnet is connected to a circuit, does the electric current not reach the required strength immediately, but gradually? [closed]

When an electromagnet is connected to a circuit, the electric current does not reach the required strength immediately, but gradually. Why? When the battery terminals of the flashlight are briefly ...
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### What does the labelling of a conductor such as: 24 W 12 V mean? Does this mean the resistance of the wire or the current?

So I came across a question where a lamp was labelled 24 W and 12 V. 2 lamps that were identical and had this labelling were then put in series with a voltage supply of 12 V. Obviously the individual ...
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### Drift of electrons in a conductor connected across battery terminals and constantly being heated

I came across this question which was suggested to me by a friend . In this question , the correct answer marked is d , which states that the conductor will have highest temperature near D end . I am ...
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### Physical meaning of $F^{0\nu}j_\nu$

In my problem I showed that $F^{\mu\nu}j_\nu$ is a contravariant 4-vector. Now the question is what is its 0-component's physical meaning, i.e. the meaning of $F^{0\nu}j_\nu$ if $F^{\mu\nu}$ is the ...
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### Why doesn't a conducting wire in a constant magnetic field experience a force in the direction of the magnetic field?

Instead of using the wire's magnetic field for deriving using Newton's third law can't we do the opposite using the magnetic field produced by magnet ? I mean why doesn't the wire simply move in the ...
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### Why don't electrons still have energy after completing a circuit with a battery?

Firstly a battery causes an accumulation of electrons in the negative terminal right? Hence the positive terminal is relatively positive and so an electric field is produced. This electric field will ...
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### Why does a real DC circuit with 1 resistor have uniform current?

Imagine a DC circuit with small but non-zero resistance in wires and large resistance in a single resistor in series with the battery, all ohmic. Connecting the battery I imagine a surge of electrons ...
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### Ohm's Law gives me different values compared to the practical experiment with a multimeter - can you explain why?

I am studying physics in high school and am trying to understand electronics. Using Ohms law I calculated VIRP values for a simple circuit with three 1000 ohm resistors and a 9V battery. I then set up ...
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### Why Doesn't moving a wire near earth generate electric current?

Why Doesn't moving a wire near earth generate electric current as the earth is a big magnet and we are changing the magnetic field by moving the wire?
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### Can Faraday Law be applied to a loop with some twists and turns in it?

Consider the above question. I have been able to solve the question understanding area vector of A and B are opposite in direction. However I have some conceptual doubts. In Faraday Law, when we say ...
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### Heat dissipation inside an extremely high inductive coil

Is it possible that for an extremely high inductive coil the oscillation paths for the electrons are so small that they can 'live' between atoms of the copper lattice without touch them and so not ...
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### Bound current and Eddy current

I Know that bound currents are due to magnetization of any material while Eddy current is due to rate of change of flux through a metal so I wanted to know whether both currents are are independent ...
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### Are voltages in series LCR circuit added vectorially?

I am trying to understand Kirchhoff's voltage law in reference to AC circuits and this is a dummy problem I have solved to show my doubt.Quoting my textbook, voltages across components in a LCR ...
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### Can non-harmful eddy currents be used to heat water? [closed]

I think after 'googling' some web sources that eddy currents are strictly localized in a volume of iron surraunded by a loaded inductive coil so can not cause an electric shock to a person while the ...
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### Is this explanation of electromagnetic induction correct? More specifically interpreting Lenz Law

When the magnet, starting with the north pole, goes towards a coil of wire (maybe a solenoid???) the magnetic field within the wire changes polarity in order to repel the north pole. This is so that ...
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### Bandwidth of a RLC Circuit

Bandwidth of an RLC circuit is defined as the angular frequency difference for which Power dissipated through circuit is half of that dissipated at resonance. What is so special about this range that ...
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### Does the drift velocity of electrons in a wire having constant length and a constant voltage applied across a depends on the area of cross section?

I used the formula Current=charge density× e × area × drift velocity i.e. i=neAV So this yield that drift velocity inversely proportional to area of cross section But the answer to this question is ...
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### Wire-wound variable resistors and thermistors

Why do we use substances with small co-efficient of temperatures in wire-wound variable resistors? Similarly, why do we use substances with high coefficient of temperature in thermistors?
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### Ohm's law and Joules heating

Ohm's law state that the ratio of V and I gives us a constant value of R provided that the temperature is kept constant throughout. However, in accordance with the joule's heating it would get heated ...
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### Is current due to a point charge moving in a circle ill-defined?

Say we've got a charge $q$ moving in a circle. Then in many texts a current due to the charge at any point on the circle is given as $I=-q/T$. Where $T$ is the time the charge takes to complete a ...
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### Do bound currents affect transport in ferromagnetic metals?

A magnetic dipole moment has the same magnetic field as if there were a current circulating in a loop in the same area. When doing problems involving magnetized materials, we often use this picture of ...
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### Is resistance or voltage more effective in reduction of power loss?

It is commonly stated that increasing voltage of the source reduces power loss. If voltage of source is increased current through the circuit increases, resulting in more power loss (than with less ...
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### Is it right that in LCR cicuit Power loss $=VI$ not equal to Power loss $= V²/R$?

I had a doubt today (this is not my homework question, I made it up). Suppose in a LCR circuit at resonance we take out power loss as $P=VI \cos\phi$ (power factor and $\cos\phi$ becomes 1) and in ...
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### Does a moving charge create a magnetic field or does a changing electric field create magnetic field or are they same?

Full question Does a moving charge create a magnetic field or does a changing electric field create magnetic field or are they same? and a moving charge always creates a changing electric field? ...
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### Current in a purely inductive circuit

To maintain the current in the purely inductive circuit why is the applied alternating voltage is equal and opposite to the induced e.m.f in an inductor . I'm unable to understand this point Why isn't ...
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### Give an elementary idea for how potential difference creates current

Resistance is explained by collision of electrons with ions. In the same way could someone please explain how a battery allows electrons to flow through the circuit. I think of it as the repulsion by ...
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### Is the current in a resistor different from that in a circuit? [duplicate]

My understanding is that since Current = Charges/Time. If there exists a resistance to the flow of charges, then that must mean the charges slow down, meaning that more time is required to pass ...
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### Is the current obtained using Ohm's law that which passes through the resistor or that which passes through the circuit?

Shouldn't the current passing through a resistor be lesser than that which passes through a circuit? My understanding is that since Current = Charges/Time. If there exists a resistance to the flow of ...
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### What happens when one connect 110V appliance to 220V supply? Is there any way to safely connect such appliance to a 220V supply without damage? [closed]

What happens when one connect a 110V appliance to a 220V supply, and vice versa? Please explain in detail. Is there any way to safely connect such an appliance to a 220V supply without causing any ...
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### Why doesn't the mean free time depend on the applied electric field?

According to classical model of conduction, if we apply an electric field E within a counductor, the mean free time does not change because the drift velocity is smaller than the thermal velocity. ...
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### Why the potential at positive terminal is considered to be high?

even though it's the electrons that move from negative terminal of the battery and gets move along the external circuit and finally enters the positive terminal of the battery and due to battery force ...
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### Transformers: How does current in primary coil change?

I was doing a question on transformers and found this really confusing question: A 100% efficient transformer converts a 240V input voltage to a 12V output voltage. The output power of the transformer ...
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### Do superconductors really have 0 resistance in reality? [duplicate]

Do superconductors really have zero resistance in reality? If yes, then by ohm's law, I = V/R. I = V/zero. I = Infinity?
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### Can a varying quantity be added to a fixed quantity

I saw a statement saying that a direct current of a units can be superimposed with an alternating current of bsin(wt) but this seems a bit contradicting as one quantity is continuously varying will ...
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### Current in the loop with two protons [closed]

Let there be a circular loop of radius r and two protons are moving in this loop with same (and constant speed $v$). They are always at diametrically opposite ends. They complete one revolution about ...
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### How to calculate the mean free time in Drude model?

According to Drude model, the average electron takes some time to go from one ion to another: this time is called mean free time. The problem is there isn't a satisfactory definition of this mean free ...
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### An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be…? [closed]

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be...? In this numerical I have a doubt that why I can't use $P=VI$ but we can use $P=\frac{V^2}{R}$...
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### What exactly is Electric Potential Difference of a cell?

What I thought Electric Potential Difference of a Battery was : • It was the factor that caused electrons in a circuit to move from negative terminal to positive terminal. •It is a variable factor w.r....
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### Induced electric field which causes current flow in a loop

I have a doubt that I am not able to find a solution to, despite having asked all my physics professors. When an EMF is induced due to a changing magnetic flux in a coil, we know that the current ...
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### Why is the heat flow in metals slower than the current flow?

When we apply a voltage across a metallic conductor, the current starts to flow almost instantaneously. But when a temperature difference is established across the same conductor, the flow of heat is ...
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### How do I precisely calculate the Current during a short-circuit event?

I am curious about this problem due to an observation last week. A standing fan I had has its wires exposed, then it short-circuited since the neutral wire was touching the live wire directly. Then I ...
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### What will happen if we try to take a voltage reading by keeping it in current mode in a multimeter?

There are different modes present in a multimeter. one is the current mode and voltage mode for their respective measurements. what will happen if one try to take a voltage reading by keeping it in ...
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### Constant volume charge density (steady-state current)

I am studying the divergence of the current density and it is said that it is zero if the volume charge density is constant. Can anyone explain me why?