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.
2,238
questions
0
votes
0answers
13 views
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 ...
0
votes
1answer
12 views
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 $= BA\cos(x)$, ...
2
votes
2answers
58 views
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 ...
0
votes
1answer
38 views
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 ...
1
vote
0answers
31 views
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 ...
-1
votes
1answer
43 views
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 ...
0
votes
1answer
38 views
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 ...
0
votes
1answer
28 views
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 ...
3
votes
1answer
93 views
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 ...
0
votes
0answers
25 views
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 ...
1
vote
3answers
55 views
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 ...
0
votes
2answers
53 views
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 ...
0
votes
2answers
45 views
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 ...
-2
votes
4answers
46 views
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?
4
votes
1answer
53 views
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 ...
0
votes
0answers
20 views
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 ...
0
votes
0answers
10 views
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 ...
0
votes
3answers
39 views
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 ...
1
vote
1answer
28 views
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 ...
1
vote
1answer
23 views
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 ...
0
votes
0answers
13 views
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 ...
0
votes
2answers
29 views
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 ...
-3
votes
0answers
15 views
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?
0
votes
2answers
39 views
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 ...
0
votes
1answer
24 views
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 ...
2
votes
0answers
19 views
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 ...
1
vote
4answers
38 views
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 ...
0
votes
1answer
32 views
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 ...
2
votes
3answers
92 views
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?
...
0
votes
2answers
28 views
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 ...
0
votes
1answer
24 views
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 ...
-4
votes
2answers
59 views
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 ...
0
votes
2answers
30 views
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 ...
0
votes
3answers
67 views
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 ...
-2
votes
0answers
31 views
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. ...
0
votes
1answer
23 views
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 ...
0
votes
0answers
19 views
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 ...
1
vote
0answers
23 views
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?
0
votes
2answers
31 views
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 ...
-1
votes
1answer
45 views
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 ...
0
votes
1answer
34 views
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 ...
0
votes
2answers
48 views
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}$...
0
votes
0answers
25 views
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....
-2
votes
0answers
43 views
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 ...
5
votes
3answers
154 views
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 ...
0
votes
3answers
44 views
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 ...
2
votes
2answers
59 views
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 ...
0
votes
1answer
44 views
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?
0
votes
1answer
27 views
How do charges away from the terminal react when the switch is flipped on?
Let us say we have a simple purely resistive DC circuit. When we flip the switch a current starts flowing which after some time becomes constant. Now, I know that the electric field across difference ...
0
votes
4answers
58 views
How does a resistor reduce current in a circuit?
I'm in year 10 and I just have a question about resistors. How exactly does a resistor reduce current?
From what I've read the current before a resistor is the same as the current after a resistor so ...
