Understanding Displacement Current in Charging a Capacitor

In summary, the problem involves finding the time rate of change of electric flux between square plates of a capacitor charged by a 0.1[A] current with 5cm sides and 4mm separation. The displacement current and its relation to the double integral of CurlB are key to solving this problem, while the other given information is not necessary. However, the given hints and approach may lead to a confusing solution.
  • #1
frozenguy
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Homework Statement


A 0.1[A] current is charging a capacitor that has square plates 5cm on each side. The plate separation is 4mm. Find (a) the time rate of change of the electric flux between the plates and (b) the displacement current between the plates.

The Attempt at a Solution


So I had hints from the teacher, and got the answer but I'm a little confused as to what I did.. Could someone help me out?
Why does the 4mm not come into play? or the 5cm?
Is I=Id always? Usually?
What was the point taking double integral of CurlB? And what equals muI+muId?


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  • #2
All you really have to do is worry about the displacement current. The other stuff is extra information for what you actually have to solve. The double integrals come from the integral forms of the Maxwell equation, it's really just a starting point.

I don't see how you got the right answer when your work is so funky.

[tex]\Phi_E = \int\int E \cdot da[/tex]

gives the electric flux. Take the time derivative of that and multiply by epsilon for the displacement current.
 

1. What is displacement current?

Displacement current is a concept in electromagnetism that describes the flow of electric charge in a region where there is a changing electric field. It was first introduced by James Clerk Maxwell in his famous equations of electromagnetism.

2. How is displacement current different from conduction current?

Displacement current and conduction current are two types of electric currents. While conduction current is the flow of electric charge through a conducting material, displacement current is the flow of electric charge through a non-conducting medium due to a changing electric field. Unlike conduction current, displacement current does not involve the physical movement of electrons.

3. What is the significance of displacement current in electromagnetic waves?

Displacement current plays a crucial role in the propagation of electromagnetic waves. It is responsible for the creation of a changing electric field, which in turn generates a changing magnetic field, and vice versa. This continuous exchange of energy between electric and magnetic fields results in the propagation of electromagnetic waves.

4. How is displacement current used in practical applications?

Displacement current has numerous practical applications, such as in the functioning of capacitors and antennas. Capacitors use displacement current to store electric charge, while antennas use it to generate and radiate electromagnetic waves for communication purposes.

5. Can displacement current be measured?

Unlike conduction current, which can be measured using a conventional ammeter, displacement current cannot be directly measured. However, its effects can be observed and measured indirectly through various experiments and calculations, as described in Maxwell's equations.

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