9
votes
Accepted
Why we use vector sum to calculate net potential in AC circuits?
The quantities themselves are not vectors. But when we consider the general case, it can be proven and seen that their calculations are similar to the calculations to add vectors. That's why , it's ...
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6
votes
Why we use vector sum to calculate net potential in AC circuits?
It's a concatenation of math tricks. We a complex analytic signal rather than a real-valued physical signal. This allows us to use the Fourier transform to reduce linear differential equations to ...
- 17.6k
5
votes
Motional EMF and Faraday's law in this case
You can adapt the wording of Faraday's law to take in your case of the straight wire moving in the magnetic field.
$$\mathscr E=-\frac{d\Phi}{dt}.$$
Here you regard $\frac{d\Phi}{dt}$ as the rate of ...
- 33.8k
5
votes
Accepted
Validity of Ohm's to non-steady currents
If you actually have charges accumulating, you need a more sophisticated model. If there's ohmic material in the circuit, Ohm's law still applies to it. But to analyze the effect of charge ...
- 17.6k
4
votes
Accepted
Doubt regarding a possible mistake in Griffiths Electrodynamics
Griffiths is right. Don't forget that that current flows outward on the plate to spread out the charge. The charge density on the plate is $\sigma=It/A$. In order to reach the area outside of $A'$ it ...
- 6,068
4
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Why we use vector sum to calculate net potential in AC circuits?
Let's work through the problem through 2 different but equivalent ways:
Trigonometric approach
In the first approach, we do the same calculation that you did. I'll use uppercase $V$ to denote the ...
- 346
3
votes
Why we use vector sum to calculate net potential in AC circuits?
When we take any component in an AC circuit with Inductor, Capacitor, and Resistor, the mapping of the current/voltage into voltage/current would involve differential operators. For example, across an ...
- 7,783
3
votes
Motional EMF and Faraday's law in this case
If you want to think about this situation in terms of Faraday's Law (which in integral form applies to any area in space), you get to pick the area to consider. Some choices of area will be useful ...
- 639
3
votes
Motional EMF and Faraday's law in this case
This is just the Lorentz force law.
Charged particles in the conductor will feel a force $\vec{F} = q\vec{v} \times \vec{B}$. This scenario (dragging a conductor through a magnetic field) is referred ...
- 7,082
3
votes
Accepted
Why electric charge does not gain net energy in closed circuit?
what prevents it from having more kinetic energy then when it started? What prevents the charges from being accelerated?
Let’s suppose that the KE of the charge carriers does increase around the ...
- 91.9k
3
votes
Does current develops instantaneously as we apply potential difference?
It all depends on the physical size of the circuit and the rate at which things change as to whether or not the speed of the electromagnetic waves need to be included in the analysis.
If that is not ...
- 91.8k
3
votes
Validity of Ohm's to non-steady currents
Ohm's law, $\mathbf J = \sigma \mathbf E$ is not a "law" in the sense of, say, $\text{div} \mathbf b =0$. The latter is a mathematical expression of the fact that there no magnetic charges, ...
- 17.1k
2
votes
Validity of Ohm's to non-steady currents
Ohms law is derived under the assumption that the current is steady, this is done via the relevant differential equation. One such example where the standard formula is completely false is for the ...
- 6,311
2
votes
Accepted
(A10) If light is an EM wave, can it interfere with electrons in a live wire, leading to a change in the wire's current?
What you describe here is exactly how radio waves work. Because of the fact that by the acceleration of surface electrons on the antenna rod zillions of polarized photons are emitted, exactly the ...
- 9,864
2
votes
What is current?
Current is the collective movement of charge across a surface per unit time.The charge that is mobile (free to move between atoms) in metal conductors is the negative charge of electrons. The positive ...
- 67.5k
1
vote
What is current?
If not please tell amd also tell what is this current made of ? Protons? Cations? Anions? Electrons? Something not yet discovered? What?
For now, you can think of the relevant charged particles that ...
- 15.7k
1
vote
Accepted
Forbidden capacitance in LC circuit connected to AC source
It's an odd question. What you've correctly found is that for the idealized whiteboard problem you have a perfect resonance that draws a divergent current from the source. But so what? Divergence ...
- 17.6k
1
vote
Constant currents do not interact with static charge. Why is that?
The main issue is that you want to write them as 3D integrals which break the covariance. It's easier to keep a Lorentz invariant from using 4D integrals.
I think that it's perhaps easier to rederive ...
- 8,641
1
vote
What is current?
In simple terms, you can understand it as, when anything with charge moves, it creates something known as "current". so, its just the flow of charges, be it electrons(-ve charges) or protons(...
1
vote
Why can the Ampere not be defined as the flow of $n$ Coulomb in $n$ seconds?
Mathematically , both are Equivalent. Practically , we might have Difficulties.
There at least 3 Issues or flaws with your way.
(1) When we say "n" , we are leaving it unknown.
When I report ...
- 413
1
vote
Accepted
Why can the Ampere not be defined as the flow of $n$ Coulomb in $n$ seconds?
That’s how it is defined, using the 1’s rather than the n’s.
You’re not really missing anything about the math/physics of the situation. Yes your definition would indeed give the same result. It’s ...
- 3,330
1
vote
Accepted
Validity of microscopic current density formula in Electrodynamics
The formula is valid. Your objection does not hold water. Remember that the current given by $dI=j\cdot dA$ is instantaneous is time. Thus only the positions of the particles and eventually its higher ...
- 8,641
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