Resistors
Resistors are components that have a predetermined resistance, which is used to control voltages and currents. Resistance determines how much current will flow through a component. Each resistor is marked with coloured stripes to indicate it’s resistance. A very high resistance allows very little current to flow and low resistance allows large amount of current to flow. Wires are made of metal because, matals have very low resistance. They allow current to flow from one point to another point without any resistance. Resistance is given in units of ohms.
Resistors can be classified into two types. They are:
• Fixed resistors
• Variable resistors
Fixed Resistors:
A fixed resistor is a component with two wires which obeys Ohm’s Law. This has a series of coloured stripes around its body. The coloured stripe signifies the resistor’s value and tolerance. Fixed value resistors are made using a variety of materials and techniques.
Variable Resistors :
Two terminal (Rheostat) and three terminal (Potentiometer) variable resistors are frequently used to adjust electronic instruments such as power supplies, oscilloscopes and function generators. The resistance of variable resistors can be varied between an upper and lower limit. The value of a variable resistor is given as it’s highest resistance value. A variable resistor is also called a potentiometer.