ContentsContents Pages

Capacitor

What is a Capacitor?

Parts of capacitor

How a capacitor works?

Uses of capacitor

Capacitance

Inductor

What is an inductor?

How does an inductor works?

Uses of inductor

Inductance

RC Circuit

What is a RC circuit?

What does a RC circuit do?

Application of RC circuit

RC CircuitWhat is a Capacitor?

A capacitor (sometimes known as condensers) is a bit like a battery, but it has a different job to do. They are used to store an electrical charge. Sometimes capacitors are used to smooth a current in a circuit. When power is supplied to a circuit that includes a capacitor, the capacitor charges up. When power is turned off, the capacitor discharges its electrical charge slowly.

Parts of a CapacitorCapacitors come in all shapes and sizes, but they usually have the same

basic components. They are composed of two conductors separated by an insulating material called a dielectric. Capacitors use dielectrics made from all sorts of materials. In transistor radios, the tuning is carried out by a large variable capacitor that has nothing but air between its plates. In most electronic circuits, the capacitors are sealed components with dielectrics made of ceramics such as mica and glass, or paper soaked in oil.

How a Capacitor works When you turn on the power, an electric charge gradually builds up on

the plates. One plate gains a positive charge and the other plate gains an equal and negative charge. If you disconnect the power, the capacitor will slowly leak away over time.

Uses of CapacitorCapacitors have many uses in electronic and electrical systems. They are

so ubiquitous that it is rare that an electrical product does not include at least one for some purpose. In car audio systems, large capacitors store energy for the amplifier to use on demand. They are also can be used as rechargeable batteries in many appliances.

CapacitanceThe amount of electrical energy a capacitor can store is called its

capacitance and is measured in units called farads (F), named for English electrical pioneer Michael Faraday (1791–1867). The bigger the capacitance, the more electricity a capacitor can store. There are three ways to increase the capacitance of a capacitor. One is to increase the size of the plates. Another is to move the plates closer together. The third way is to make the dielectric as good an insulator as possible. Due to this, we can calculate the value of capacitance as follows:

In practice, most of the capacitors we use are just fractions of a farad—typically microfarads (μF), nanofarads (nF), and picofarads (pF).

What is an Inductor?An inductor is a passive electronic component that stores energy in the

form of a magnetic field. In its simplest form, an inductor consists of a wire loop or coil. The inductance is directly proportional to the number of turns in the coil. Inductance also depends on the radius of the coil and on the type of material around which the coil is wound.

The standard unit of inductance is the henry abbreviate dH. This is a large unit. More common units are the microhenry, abbreviated µH (1 µH =10-6H) and the millihenry, abbreviated mH (1 mH =10-3 H). Occasionally, the nanohenry (nH) is used (1 nH = 10-9 H).

Symbol of inductor

Simple circuit with inductor

How Does An Inductor Works?When current first starts flowing in the coil, the coil wants to build up a

magnetic field. While the field is building, the coil inhibits the flow of current. Once the field is built, current can flow normally through the wire. When the switch gets opened, the magnetic field around the coil keeps current flowing in the coil until the field collapses.

Uses of InductorInductor is used as the energy storage device in many switched-mode

power supplies to produce DC current. The inductor supplies energy to the circuit to keep current flowing during the "off" switching periods. Inductors are used extensively with capacitors and resistors to create filters for analog circuits and in signal processing. Alone, an inductor functions as a low-pass filter, since the impedance of an inductor increases as the frequency of a signal increases. Contactless sensors are prized for their reliability and ease of operation and inductors can be used to sense magnetic fields or the presence of magnetically permeable material from a distance. Inductive sensors are used at nearly every intersection with a traffic light to detect the amount of traffic and adjust the signal accordingly. These sensors work exceptionally well for cars and trucks, but some motorcycles and other vehicles.

InductanceIn electromagnetism and electronics, inductance is the property of an

electrical conductor by which a change in current flowing through it induces an electromotive force in both the conductor itself and in any nearby conductors by mutual inductance.

The formulae of inductance is:

What is a RC circuit?A resistor–capacitor circuit (RC circuit) is an electric circuit composed of

resistors and capacitors driven by a voltage or current source. A simple RC circuit is composed of one resistor and one capacitor.

What does a RC circuit do?They play an important role in the transmission of electrical signals as in

nerve cells. When a circuit consists of only a charged capacitor and a resistor, the capacitor will discharge its stored energy through the resistor. The voltage across the capacitor, which is time dependent, can be found by using Kirchhoff's current law, where the current charging the capacitor must equal the current through the resistor. This results in the linear differential equation,

where C= capacitance of capacitor.

Solving this equation for V yields the formula for exponential decay:

where V0 is the capacitor voltage at time t = 0.

The time required for the voltage to fall to is called the RC time constant and is given by

Application of RC CircuitHigh-pass filter

A high-pass filter is an electronic filter that offer easy passage of a high-frequency signal from source to load and difficult passage to a low-frequency signal. Capacitive high-pass filters insert a capacitor in series with the load while inductive high-pass filters insert a resistor in series and an inductor in parallel with the load. The cutoff frequency for a high-pass filter is that frequency at which the output (load) voltage equals 70.7% of the input (source) voltage. Above the cutoff frequency, the output voltage is greater than 70.7% of the input, and vice versa.

Low-pass filter

A low-pass filter is the opposite of a high-pass filter. It offers easy passage to low-frequency signals and difficult passage to high-frequency signals. Inductive low-pass filters insert an inductor in series with the load while capacitive low-pass filters insert a resistor in series and a capacitor in parallel with the load. The cutoff frequency for a low-pass filter is that frequency at which the output (load) voltage equals 70.7% of the input (source) voltage. Above the cutoff frequency, the output voltage is lower than 70.7% of the input, and vice versa.

Band-pass filter

Band-pass filters are designed by combining the properties of low-pass and high-pass into a single filter. These types of filters will only allow passage of those frequencies that are neither too high nor too low.

Band-pass filters are widely used in wireless transmitters and receivers. The main function of such a filter in a transmitter is to limit the bandwidth of the output signal to the band allocated for the transmission. This prevents the transmitter from interfering with other stations. In a receiver, a band-pass filter allows signals within a selected range of frequencies to be heard or decoded, while preventing signals at unwanted frequencies from getting through.