EXPERIMENT NO .1 AIM :- Introduction to active and passive electronic components and accessories APPARATUS:- Resistors,Capacitors,Diodes,Transistors. THEORY:- Electronic Components are categorized into Passive components:- Resistors,Capacitors, Active components :- Diodes,Transistors 1) RESISTOR -A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. -Resistance:A measure of the degree to which an object opposes an electric current through it. -Resistance can be evaluated as, R=V/I Symbol Of Resistor is shown below Value Identification Of Resistor using resistor colour code The resistance value, tolerance, and wattage rating are generally printed onto the body of the resistor as numbers or letters when the resistors body is big enough to read the print, such as large power resistors. But when the resistor is small such as a 1/4W carbon or film type, these specifications must be shown in some other manner as the print would be too small to read. So to overcome this, small resistors use coloured painted bands to indicate both their resistive value and their tolerance with the physical size of the resistor indicating its wattage rating. These coloured painted bands produce a system of identification generally known as a Resistors Colour Code.
Calculating Resistor Values The Resistor Colour Code system is all well and good but we need to understand how to apply it in order to get the correct value of the resistor. The "left-hand" or the most significant coloured band is the band which is nearest to a connecting lead with the colour coded bands being read from left-to-right as follows; Digit, Digit, Multiplier = Colour, Colour x 10 colour in Ohm's (Ω's) For example, a resistor has the following coloured markings; Yellow Violet Red = 4 7 2 = 4 7 x 102 = 4700Ω or 4k7. The fourth and fifth bands are used to determine the percentage tolerance of the resistor. Resistor tolerance is a measure of the resistors variation from the specified resistive value and is a consequence of the manufacturing process and is expressed as a percentage of its "nominal" or preferred value. The Different Types of Resistors There are many different Types of Resistors available to the electronics constructor, from very small surface mount chip resistors up to large wirewound power resistors. The principal job of a resistor within an electrical or electronic circuit is to "resist"
All modern fixed value resistors can be classified into four broad groups; • Carbon Composition Resistor - Made of carbon dust or graphite paste, low wattage values • Film or Cermet Resistor - Made from conductive metal oxide paste, very low wattage values • Wire-wound Resistor - Metallic bodies for heatsink mounting, very high wattage ratings 2) CAPACITOR - A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. - Capacitance is the ability of a body to store an electrical charge. - Capacitance can be evaluated as C=Q/V
- Symbol of Capacitance is shown below Final equation for the capacitance of a capacitor as: C = εA/d Where ε=permittivity of dielectric material A=cross section area of conducting plate d =distance between two plates The job of a capacitor is to store charge onto its plates. The amount of electrical charge that a capacitor can store on its plates is known as its Capacitance value and depends upon three main factors. • The surface area, A of the two conductive plates which make up the capacitor, the larger the area the greater the capacitance. • The distance, d between the two plates, the smaller the distance the greater the capacitance. • The type of material which separates the two plates called the "dielectric", the higher the permittivity of the dielectric the greater the capacitance. Types of Capacitor There are a very, very large variety of different types of capacitor available in the market place and each one has its own set of characteristics and applications Dielectric Capacitor Dielectric Capacitors are usually of the variable type were a continuous variation of capacitance is required for tuning transmitters, receivers and transistor radios. Variable dielectric capacitors are multi-plate air-spaced types that have a set of fixed plates (the stator vanes) and a set of movable plates (the rotor vanes) which move in between the fixed plates.