Question on current flow through polarized capacitors

In summary, a polarized capacitor can discharge through the positive terminal without charging the dielectric.
  • #1
Idea04
194
1
If a current enters the negative terminal of a polarized capacitors, does the negative plate have to be fully charged before it passes through to the positive plate.
 
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  • #2
If a current enters the negative terminal of a polarized capacitors, does the negative plate have to be fully charged before it passes through to the positive plate.

No, the plates do not get charged at all. It is the dielectric that holds the charge and it is charged by the difference in voltage between the plates.

Polarity is only important because electrolytic capacitors need it to be the right way around to form the dielectric.
 
  • #3
so if I understand this properly, a polarized capacitor can fully charge without discharging through the positive terminal.
 
  • #4
Absolutely not.

It is just that a polarized capacitor must not be connected with the + terminal negative with respect to the - terminal.
They are often used where there is a DC voltage present and this must be connected the right way around.
They can explode in a very spectacular and messy way if you do it the wrong way.
 
  • #5
Any kind of capacitor charges through both plates and also discharges through both plates.

The electrolytic capacitors have a very thin insulating layer on Aluminium which can be destroyed by electrolytic action if you put a reversed voltage on the capacitor.

They are quite rugged and you can put an alternating voltage on them, but it is essential that they do not have a steady DC voltage of the wrong polarity on them.

This coating is not part of the charge applied to the capacitor. The charge is actually in the coating which acts as a dielectric.
 
  • #6
Thank you for the response, it has been very helpful. But if a voltage is applied to the capacitor, will the current flow directly through the capacitor, or will the voltage have to charge the dielectric before the current can pass through.
 
  • #7
The DC current only goes into the capacitor to charge it. When you discharge the capacitor, it comes back out again.
It does not really "pass through" the capacitor.

This applies to any capacitor.

The charge on the capacitor eventually gives the capacitor a voltage on it equal to the applied voltage and at that time no more charging current flows into the capacitor. You can take the capacitor and put it away and the charge will still be there.
When you connect it to a conductor between the plates of the capacitor, current will flow out of the capacitor into the conductor. If you leave it there long enough, there will be no more current flowing and the capacitor voltage will drop to zero.

Electrolytic capacitors behave exactly like other capacitors except that if there is a dc voltage present it should be the right way around.

What might not be obvious is that AC voltages and currents can pass through capacitors while DC voltages and currents cannot pass through them.
 

1. What is a polarized capacitor?

A polarized capacitor is a type of capacitor that is designed to operate with a specific polarity, meaning that the positive and negative terminals must be connected correctly in a circuit. They are typically used in DC circuits and are commonly found in electronic devices.

2. How does current flow through a polarized capacitor?

Current flows through a polarized capacitor in the same way it flows through a regular capacitor. When a voltage is applied to the capacitor, one plate becomes positively charged and the other becomes negatively charged. This creates an electric field between the plates, allowing current to flow through the capacitor.

3. What happens if a polarized capacitor is connected with the wrong polarity?

If a polarized capacitor is connected with the wrong polarity, it can lead to the capacitor becoming damaged or even explode. This is because the electric field will be reversed, causing a buildup of charge and ultimately leading to a breakdown of the capacitor's dielectric material.

4. How does the current flow change when a polarized capacitor is fully charged?

When a polarized capacitor is fully charged, the flow of current will stop. This is because the capacitor reaches its maximum capacity to store charge and the electric field between the plates can no longer be increased.

5. Can polarized capacitors be used in AC circuits?

No, polarized capacitors should not be used in AC circuits as they are designed to work with a specific polarity. In AC circuits, the direction of the current changes constantly, so using a polarized capacitor could lead to damage or malfunction.

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