# Why can a capacitor be charged by a battery (DC)?

• Yoyo G
In summary, the conversation discusses the concept of DC-blocking in capacitors and how it allows for the charging process to occur. The speaker is confused about how this works and is seeking clarification from others. They mention reading about capacitors but still not fully understanding the process. They also provide a reference for further explanation.
Yoyo G
Hello there,
I'm perplexed as to why the capacitor is DC-blocking, but the battery (DC) may charge the capacitor.
I'd never considered it until I recently read it in a book. I honestly have no idea what's going on.
If anyone has any idea why this happens, please let me know.
I've read some articles like the guide to capacitors, but I still don't know how it works.
Thanks!

In charging process of condenser
Plus charges are gathering to one plate. Minus chargers are gathering to another or in other words plus charges are leaving from another plate, so we see as if plus current go through beyond the plates. DC-blocking you say comes after a full charge.

Ref. https://www.feynmanlectures.caltech.edu/II_18.html Fig.18-2

Last edited:
Yoyo G said:
I'm perplexed as to why the capacitor is DC-blocking, but the battery (DC) may charge the capacitor.
A bucket can also block the flow of water, but you can still fill (and empty) it.

gleem, nsaspook, Averagesupernova and 1 other person

## 1. How does a capacitor get charged by a battery?

When a battery is connected to a capacitor, the battery's positive terminal pushes electrons onto one plate of the capacitor, while the negative terminal pulls electrons away from the other plate. This creates an electric field between the plates, causing one plate to accumulate a positive charge and the other to accumulate a negative charge. This process continues until the capacitor is fully charged.

## 2. Why can't a capacitor be charged by an AC source?

Unlike a battery, which provides a constant flow of electrons in one direction, an AC source alternates the direction of electron flow. This means that the capacitor's plates will accumulate opposite charges, which will cancel each other out and prevent the capacitor from becoming fully charged.

## 3. What happens to the voltage of a capacitor when it is charged by a battery?

As the capacitor becomes charged, the voltage across its plates increases. This is because the electric field between the plates becomes stronger as more charge is stored on the plates. Once the capacitor is fully charged, the voltage across its plates will be equal to the voltage of the battery.

## 4. Can a capacitor be charged by any type of battery?

Yes, a capacitor can be charged by any type of battery as long as the battery's voltage is greater than the voltage rating of the capacitor. However, different types of batteries may have different charge and discharge rates, which can affect the speed at which the capacitor becomes fully charged.

## 5. Why is a capacitor used in conjunction with a battery in electronic circuits?

Capacitors are often used in electronic circuits to store electrical energy and release it when needed. This can help to smooth out fluctuations in the power supply and provide a stable source of energy for the circuit. Additionally, capacitors can be used to block or filter certain frequencies of electrical signals, making them useful for a variety of applications in electronic devices.

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