Understanding Electrical ResistanceDear friends, today the topic of my lecture is - Understanding Electrical Resistance.
In this lecture we will try to understand what is meant by the resistance when electricity passes through a material.
To start with we already know that materials can be broadly put under two categories - conductor and insulator, depending upon whether they allow the electric current to pass through them or not.
So whenever we try to pass electric current through a material it will try to impede it's flow and this property is known as electrical resistance. Accordingly the current (more or less) will flow through it depending upon this resistance
Electrical resistance is the basic property which is utilized in designing of electrical circuits ranging from basic electrical wiring in our houses to wiring in complicated computerised electro-mechanical super machines.
Metals like copper, aluminium, iron etc are good conductors of electricity and their electrical resistance is less - copper being the minimum. This property of copper is used in the electric wiring in our houses where copper wires are often used. When electricity flows through these wires you can not touch them as you will get the shock and to protect us from the shock these wires are covered with some non conducting material (insulators) like rubber or plastic etc.
Let us understand the electrical resistance more clearly by taking an example of a metal wire. It will have some electrical resistance. It is seen by experiments that if we increase the length of this wire the resistance increases proportionally. On the other hand if we increase the diameter (thickness) of this wire the resistance decreases in inverse proportion. So these are the properties used in designing the resistances for a particular purpose.
The famous Ohm's law in physics states that if a voltage V (unit-Volts) is applied across a conductor having a resistance of R (unit-Ohm) and due to this a current I (unit-Ampere) flows through it then -
V = I x R
This is the basic mathematical relation of resistance with the applied voltage and current flowing through it.
When a sufficient electric current flows through a metal wire which has bigger resistance (like the one we have in our electric heater), the wire starts heating up and this property is used in electrical heaters, geysers etc.
I hope that I have made the concept of electrical resistance clear to you. Thank you.