ELECTRICITY AND CIRCUITS

An electric current is a flow of microscopic particles called ELECTRONS flowing through wires and electronic components. An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow.
We use electricity in our daily life for many purposes to make our tasks easier. For example, we use electricity for illuminating our home, for motors bikes, for decoration, to operate pumps that lift water from wells or from ground level to the roof top tank. Due to electricity, it’s possible to light roads, offices, markets and factories even after sunset. Electricity helps us to continue working at night. We use electricity in the form of torch where there is no electricity lines.
An electronic circuit can usually be categorized as an analog circuit, a digital circuit or a mixed-signal circuit. Analog electronic circuits are those in which current or voltage may vary continuously with time to correspond to the information being represented. Analog circuitry is constructed from two fundamental building blocks: series and parallel circuits. In a series circuit, the same current passes through a series of components. A string of Christmas lights is a good example of a series circuit: if one goes out, they all do. In a parallel circuit, all the components are connected to the same voltage, and the current divides between the various components according to their resistance.A simple schematic showing wires, a resistor, and a battery.Analog circuits are very commonly represented in schematic diagrams, in which wires are shown as lines, and each component has a unique symbol. Analog circuit analysis employs Kirchhoff’s circuit laws: all the currents at a node (a place where wires meet) must add to 0, and the voltage around a closed loop of wires is 0. Wires are usually treated as ideal zero-voltage interconnections; any resistance or reactance is captured by explicitly adding a parasitic element, such as a discrete resistor or inductor. Active components such as transistors are often treated as controlled current or voltage sources: for example, a field-effect transistor can be modeled as a current