A Resistor is an electrical component that resists the flow of electrical current in electronic circuits, in other term, where there is high resistance in a circuit the flow of current is small, where the resistance is low the flow of current is large. And so we can control the flow of current by changing the value of the resistance, which passes through the electronic circuits, when a resistor is introduced to a circuit the flow of current is reduced. The higher the value of the resistor the smaller/lower the flow of current, the resistance is measured in ohms.
Resistance, voltage and current are connected in an electrical circuit by Ohm’s Law:
R = V / I.
The most common schematic symbol for a resistor is a zig-zag line but in a circuit diagram the symbol used for a resistor varies:
The Ohm (symbol: Ω, called Omega) is the SI unit of electrical resistance, named after Georg Simon Ohm, Higher resistance values are represented by “k” (kilo-ohms) and M (meg ohms).
150 000 Ω = 150k,
1 500 000 Ω = 1M5
The resistors are typically constructed of metal wire or carbon, and engineered to maintain a stable resistance value over a wide range of environmental conditions.Unlike lamps, they do not produce light, but they do produce heat as electric power is dissipated by them in a working circuit. Typically, though, the purpose of a resistor is not to produce usable heat, but simply to provide a precise quantity of electrical resistance.
Resistor color codes
Resistors have colored stripes on them that represent their resistance value. They also have a colored stripe that represents a tolerance value.Three or four colored stripes in close proximity designate the resistance value. The first two or three bands represent a numerical value with the last band representing a multiplier of that value.
The resistors are the most common components are the basis for all electronic circuits, their ability to restrict the flow of electric current allows them to protect electronics components from circuit overload or destruction. Diodes, for example, are current sensitive and so are almost always coupled with a resistor when they are placed inside of a circuit. Resistors are also combined with other electrical components to form important fundamental circuits. They can be paired with capacitors to perform as filters or voltage dividers. Another role is that of the formation of oscillatory AC circuits when they are coupled with capacitors and inductors.