Application of Capacitors

Capacitor

A capacitor is a device that can store electric charge and normally consists of two conducting objects (usually plates or sheets) placed near each other but not touching. Basically, capacitors consist of two metal plates separated by an insulator. The insulator is called a dielectric. (e.g., polystyrene, oil, or air).  Capacitors are one of the most used and useful electronic components used in any modern electronic and electrical circuit and devices.

Application of Capacitors

Capacitors are used in a wide range of electronic and electrical applications due to their ability to store and release electrical energy. Some of the most common applications of capacitors include:

1. Energy storage: Capacitors are used to store electrical energy in electronic circuits. They can be used to smooth out voltage fluctuations in power supply circuits, and in combination with other components, can be used to filter unwanted noise or interference from a signal.
2. Timing: Capacitors are commonly used in timing circuits, such as oscillators, to control the frequency and duration of electrical signals.
3. Power factor correction: Capacitors can be used in power factor correction circuits to improve the efficiency of electrical systems by reducing the amount of reactive power drawn from the grid.
4. Motor starting and power conditioning: Capacitors can be used in electric motors to provide starting torque and improve the power factor of the motor.
5. Audio and signal processing: Capacitors are used in audio and signal processing circuits to filter and tune signals, and to couple signals between different stages of a circuit.
6. Radio frequency (RF) circuits: Capacitors are used in RF circuits to block DC signals while allowing AC signals to pass through, and to tune resonant circuits.
7. Sensors: Capacitive sensors use changes in capacitance to detect changes in position, pressure, humidity, and other environmental factors.

These are just a few examples of the many applications of capacitors. Capacitors are versatile components that are widely used in electronics and electrical systems, and new applications for capacitors are constantly being developed.

Charging a Capacitor

In most practical applications, each conductor of a capacitor initially has zero net charge. If we connect a capacitor, a resistor, and a voltage source in series, the capacitor will be charged up until its voltage value is equal to the voltage source. A capacitor can store energy, and a resistor placed in series with it will control the rate at which it charges or discharges. This produces a characteristic time dependence and a crucial parameter that describes a capacitor’s rate of charge and discharge:

The time constant, or circuit time delay, represents the time response of the circuit when an input step voltage or signal is applied.

The charging current asymptotically approaches zero as the capacitor becomes charged up to the battery voltage. The time required for the capacitor to be fully charged is equivalent to about 5 time constants or 5T. Thus, the transient response or a series RC circuit is equivalent to 5 time constants.

Capacitors together with resistors, form so-called RC circuits, and they are a common element in electronic devices and play an important role in the transmission of electrical signals. They are used to control the speed of a car’s windshield wipers and the timing of traffic lights; they are used in camera flashes and in many other electronic devices, such as audio filters and oscillators.

Discharging a Capacitor

Discharging a capacitor means releasing the charge stored within the capacitor. RC discharging circuits use the inherent RC time constant of the resistor-capacitor combination to discharge a capacitor at an exponential rate of decay.