Conductors, Semiconductors, Insulators

Solids can be classified on the basis of electrical conductivity as:
1) Conductors
2) Semiconductors
3) Insulators

Conductors: The Substances which easily allow electric current pass through them are called conductors. E.g. Copper, Aluminium has large no. of free electrons.

Conductors contain no forbidden energy gap between valance band and conduction band. They overlap each other as shown in the given image. Without supplying any additional energy valance electrons become free electrons which make metals like Copper, Aluminium good conductors of electricity.

Capacitors

The electronic components that are used to store the charge are called Capacitors. This capability of capacitors to store the energy (Charge) is called capacitance. Capacitance is measured in Farads (F). Farad is a very high unit of capacitance. Lower units are Micro Farad (µF) and Pico Farad (pF).

Capacitor consists of two conducting plates that are separated by an insulating material which is known as dielectric. Capacitor offers very low impedance to AC but it blocks DC. The reason behind this is that
X_C =1/2πfc and for AC frequency is 50-60 Hz but for DC frequency is 0 hence X_C= Infinite.

Capacitors are classified on the basis of die electric used between them. Some well known types of Capacitors are as Follows:

1) Mica Capacitors: These types of Capacitors are constructed with the help of two Aluminium foils separated by a mica sheet. These plates are connected to two electrodes. The entire unit is encapsulated in a plastic housing. These type of Capacitors are used for small capacitance values ranging from 5 pF to 10µF. These Capacitors can operate at up to 500V and has leakage current about 1000MΩ.


















2) Paper Capacitors: These types of capacitors are

Resistors and Their Types

The components which resist or oppose the flow of electrons in any electrical or electrical circuit is called resistor. The force by which it resists flow of current is called resistance. It is measured in Ohms (Ω). Resistors are used to limit current flowing through a circuit or to divide the voltage in a circuit.

Types of Resistors
i) Fixed Value Resistors.
ii) Variable Value Resistors.


Fixed Resistors: The Resistors whose value remain same and can’t be changed is called fixed value resistor. Fixed value resistors can be of following types:

a) Carbon Resistors: These types of Resistors are manufactured from mixture of carbon or graphite and clay. These are also made in metalized type by decomposing a homogeneous film of pure carbon or metal over glass, ceramic or any other insulating core.

 
b) Wire Wound Resistors: These types of resistors are made