# Help with understanding capacitance

• johnnyies
In summary: This means that capacitors have an effect on AC signals and can be used to filter them, for example to reduce noise.
johnnyies
my book does not fare well in explanations, thus I have a few questions

if the capacitor plates hold energy, how does this energy become released in certain applications? what are some common applications of capacitors?

if the voltage difference in parallel capacitors are the same, why is the voltage difference in series capacitors different? why do they add up to be the overall voltage of the battery?

sorry if they're stupid questions, book sucks kinda.

Hi johnnyies!
johnnyies said:
if the capacitor plates hold energy, how does this energy become released in certain applications? what are some common applications of capacitors?

It's released (not all at once, but exponentially) when the circuit (joining the two plates "the long way round") is completed.
if the voltage difference in parallel capacitors are the same

It has to be, or charge would flow between the two capacitors.
… why is the voltage difference in series capacitors different? why do they add up to be the overall voltage of the battery?

For the same reason as for resistances.

(There's nothing "magic" about capacitors … just think about what the charge does … the total charge is conserved, and it moves if there's a voltage difference )​

yes, but how do we release that charge from the capacitors?

In a DC circuit the charge stored can only be released if you give the capacitor a path to release it through. For instance you could charge a capacitor using a DC power supply and then disconnect the capacitor and use it as a temporary power source in another circuit.

You might be struggling to understand them because you're focusing on its DC applications, in DC circuits with ideal conditions capacitors have little use. However, capacitors are extremely useful in AC circuits due to the impedance being affected by frequency (in proportion to its capacitance).

In AC circuits its useful to think of capacitors in terms of impedance. Its impedance is higher with lower frequencies (with a frequency of 0 it's open circuit) and its impedance is lower when the frequency is higher (at infinite frequency it's short circuit).

## What is capacitance and how does it work?

Capacitance is the ability of a capacitor to store electric charge. It works by using two conductive plates separated by an insulating material, or dielectric. When a voltage is applied to the capacitor, one plate accumulates positive charge and the other accumulates negative charge, creating an electric field between them. The amount of charge that can be stored is directly proportional to the voltage applied.

## What factors affect the capacitance of a capacitor?

The capacitance of a capacitor is affected by several factors, including the distance between the plates, the surface area of the plates, and the type of dielectric material used. The distance between the plates is inversely proportional to the capacitance, meaning that the closer the plates are, the higher the capacitance. Similarly, the larger the surface area of the plates, the higher the capacitance. Different dielectric materials have different permittivity values, which also affect the capacitance.

## How is capacitance measured?

Capacitance is measured in units called farads (F). However, this unit is often too large for practical use, so capacitors are typically measured in smaller units such as microfarads (μF) or picofarads (pF). To measure capacitance, a multimeter or a capacitance meter can be used. The capacitance value can also be calculated using the formula C=Q/V, where C is the capacitance, Q is the charge stored, and V is the voltage applied.

## What are some common applications of capacitance?

Capacitors have a wide range of applications in various electronic circuits. They are commonly used in power supplies to filter out unwanted noise, in audio equipment to store and release energy for amplification, and in timing circuits to control the frequency of oscillators. Capacitors are also used in electronic devices such as smartphones and computers to store energy and regulate voltage.

## How does capacitance differ from resistance?

While capacitance and resistance are both properties that affect the flow of electricity, they have different functions. Capacitance is the ability to store charge, while resistance is the opposition to the flow of current. Capacitors store energy, while resistors dissipate energy. Another key difference is that capacitance is affected by frequency, while resistance is not. In a circuit, resistance limits the current flow, while capacitance can store and release energy to maintain a steady current.

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