Basic Knowledge about Electrical and Electronic

1.CAPACITOR

A capacitor is an electrical device that can store energy in the electric field between a pair of closely spaced conductors (called 'plates'). When voltage is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each plate.Capacitors are used in electrical circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals and this makes them useful in electronic filters. Capacitors are occasionally referred to as condensers. This is now considered an antiquated term. The capacitor's capacitance (C) is a measure of the amount of charge (Q) stored on each plate for a given potential difference or voltage (V) which appears between the plates:

In SI units, a capacitor has a capacitance of one farad when one coulomb of charge causes a potential difference of one volt across the plates. Since the farad is a very large unit, values of capacitors are usually expressed in microfarads (µF), nanofarads (nF), or picofarads (pF).

2 DIODE

A Diode is a semiconductor device, which allows the current to flow easily in one direction, and provides a very high resistance when the current flows in the reverse direction. The direction in which current flow easily, with little resistance, is called forward direction and the opposing direction is called reverse direction.

A diode has two leads, anode and cathode. The conventional current can flow from anode to the cathode but will face very high resistance when tries to flow from cathode to the anode.

The cathode is often marked by a band at one end. There are several kinds of diodes, each with features that suit it for a particular. Three of the main types are:

1  1)    The junction diode

2  2)The point-contact diode

    3)The zener diode

3) Resistors

Electrons move easily through some materials than others when a voltage is applied. Opposition to current is called resistance.

Numerically, resistance can be defined as the ratio of the potential difference (V) across its ends to the current (I) flowing through its.

i.e. R=V/I

Resistance of a conductor depends on its material, length and area of cross section.

A conductor has low resistance. Copper is a very good conducting material and is used as connecting wires in circuits. Short and thick wires have less resistance than long thick ones.

An insulator has very high resistance and is a poor conductor. Plastic such as polythene and pvc and pass tiny currents even with high voltages;they are used as insulation to cover connecting wire.

                                         

A semiconductor falls in between a conductor and a insulator. Silicon is one of the example which is use to make transistors and ICs. The S.I. unit of resistance is ohm.

Resistance are of two types i.e. variable resistor and fixed value resistors.

Basically, the value of variable resistor stated on its body but if you want to know the value of fixed value resistors then you must know about the colour code system of the resistance which shows below.

NUMBER                    COLOUR

0                                    BLACK

1                                    BROWN

2                                    RED

3                                    ORANGE

4                                    YELLOW

5                                    GREEN

6                                    BLUE

7                                    VOILET

8                                    GREY

9                                    WHITE