Unit-2 chapter-7 Pg:- 75, 76, 77, 78|took more information from khan academy|

Resistance is a simple word, it means to slow down or refuse. Resistors play a big role in our everyday lives, it helps us charge our phones, use TVs, light bulbs, heaters, etc. Why is it used and how does it work?

Resistors are made up of things that don't let electricity pass through easily, like ceramic, plastic, and glass. It is used to slow down and reduce the current flow through components like a lamp or phone. If too much current flows through these components they will overwhelm the fuse, so we use resistors that lower the current by slowing it down.

Resistance is measured in ohms, and the formula of resistance is R = V/I but there is a common misunderstanding that comes to mind when we think about it, if we increase the voltage or current, shouldn't the resistance increase or decrease, well no, according to ohms law, every ohmic material will have a constant resistance, which means factors like voltage and current can't increase resistance. How to increase resistance then? In inorder to increase or decrease resistance we need to make changes in the resistor itself, by changing its length and area. the resistance of the resistor is inversely proportional to the crossectional area. Another important factor that changes the resistance is the natural resistivity of the material, which is represented by the Greek letter rho

Rho==>

If we try and make an equation that determines the factors of resistance then the formula will look something like this

If we change any of these factors then resistance will also change. The unit of Rho is ohmmeter, for example, the resistivity of copper is 1.68 * 10 ^ -18 ohmmeter, which is barely anything, because as we know copper is less resistive, current flows through it as if it is not even there, but on the other hand the resistivity of rubber is 10 ^ 13 ohmmeter, which is a huge number because of how less conductive rubber is. Electrical conductivity is denoted by the symbol "sigma":

"Sigma"==>

Try explaining using your logic, why doesn't Resistivity change when you change voltage and current.