A capacitor is an electrical component which stores and releases electricity in a circuit, much like a rechargeable battery does. However, a capacitor stores potential energy in an electrical field, whereas batteries accumulate energy in the form of a chemical energy, and then convert this into an electrical energy. A capacitor will only pass alternating current (AC) and does not pass direct current (DC), and they have become an important element of an electrical circuit and one that is commonly used. Capacitors have very quick and easy charge and discharge capabilities, and so are used often in industrial applications, but also for consumer electronics and for things like wearable smart devices.
How do capacitors work?
Capacitors are also known as ‘condensers’ and are a basic component when building an electrical circuit. They store electrostatic energy in an electrical field, and then dispense this energy to a circuit as it is needed. It allows the flow of AC current, but blocks DC current, and this is an important factor in avoiding the hazardous breakdown of a circuit.
The capacitor is a very small device, usually with a main body that is protected by different types of material, most commonly this will be either plastic or ceramic. The main features of capacitors are:
- Charging and discharging electrical energy very quickly
- Filtering out unwanted frequencies
- Can handle power loss efficiently, making power production more economical
- They are less sensitive to temperatures than other components, making them resilient to high voltages
- They can handle high voltage applications and are therefore suitable for high frequency uses
- Have a long lifecycle, often being effective in a circuit for 10-15 years
What problems can occur in an electrical circuit if you choose the wrong capacitor?
While a capacitor will work very effectively if installed properly in a circuit, it can cause serious problems if this is not the case. An incorrect capacitor can mean it is the wrong material, the wrong capacitor rating or the wrong physical size. This can lead to various issues when the circuit is activated, such as:
- A loss of power to the circuit
- An unstable circuit
- The capacitor fails to stabilise a high voltage
- You receive unwanted noise
- There is a mechanical stress in the capacitor itself or other elements of the circuit
- Circuit failure
- Damaged capacitor – each capacitor is built with an external casing and if the incorrect capacitor is used, this casing can develop cracks, perhaps through overheating. This can lead to the chemical insulation inside leaking onto the circuit board. This exposes the circuit board to reactive compounds and can have a series of serious knock-on effects.
The outer casing of a capacitor is known as the dialectic. This is a very important property, and common types of dialectic are films, such as polyester film, metallised film, polypropylene film, PTE film and polystyrene film capacitors, also ceramic, electrolytic and paper dialectics are common.
Please note that this section is for information purposes only. Anyone using equipment referred to in this section must be suitably qualified and/or experienced within the respective field. If in doubt before use, please consult a qualified electrician or engineer & thoroughly read all instruction booklets.