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crx

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- Thread starter crx
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In summary: From Maxwells equations,Curl H = sigma E + e e0 dE/dt = e e0/d dV/dt,so a varying voltage across the capacitor creates a magnetic field, even when the conductivity sigma = 0.

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crx

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- #2

Bob S

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The derivative is

So it requires a current

Bob S

- #3

Bob S

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Q = CV = e

Now insert a dielectric of relative permittivity e and thickness d and area A in the capacitor. Now

Q' = C'V

where C = ee

There is a current in the external circuit that increases the charge Q on the plates to maintain the voltage V on the capacitor.

Bob S

- #4

crx

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Bob S said:

Q = CV = e_{0}AV/d.

Now insert a dielectric of relative permittivity e and thickness d and area A in the capacitor. Now

Q' = C'V

where C = ee_{0}A/d

There is a current in the external circuit that increases the charge Q on the plates to maintain the voltage V on the capacitor.

Bob S

Yes,but this is because of the dielectric molecules are shielding and weakening the electric field, so the capacitor will need more charges to reach the power supply voltage, so there will be a current in the external circuit.

What i would like to know is that if a plate capacitor with no dielectric in vacuum (with a pretty large gap ), connected to a AC supply, will have a magnetic field exactly in the area between the plates where there are no moving charges, but only variable electric field...

- #5

Bob S

- 4,662

- 7

From Maxwells equations,crx said:Yes,but this is because of the dielectric molecules are shielding and weakening the electric field, so the capacitor will need more charges to reach the power supply voltage, so there will be a current in the external circuit.

What i would like to know is that if a plate capacitor with no dielectric in vacuum (with a pretty large gap ), connected to a AC supply, will have a magnetic field exactly in the area between the plates where there are no moving charges, but only variable electric field...

Curl H = sigma E + e e

so a varying voltage across the capacitor creates a magnetic field, even when the conductivity sigma = 0.

Bob S

A magnetic field is a region in space where a magnetic force can be detected. It is created by moving electric charges and can exert a force on other moving charges.

A magnetic field is produced by electric currents, which are generated by moving charges. It can also be produced by permanent magnets or changing electric fields.

Displacement current is a concept in electromagnetism that describes the flow of electric charge that is not carried by actual moving particles, but by changing electric fields. It was introduced by James Clerk Maxwell to explain the behavior of electric currents in a vacuum.

According to Maxwell's equations, a changing electric field can produce a magnetic field, and vice versa. Displacement current is one of the sources of magnetic fields, along with actual electric currents.

Magnetic fields and displacement current have numerous practical applications, including in generators and motors, magnetic levitation systems, particle accelerators, and medical imaging devices such as MRI machines.

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