Basic Idea of Temperature Coefficient and increase/decrease in resistance due to Temperature

#Channel1

A resistor's  tempt. coefficient of resistance tells you how much its value changes as its temperature changes.
unit = ohm /ohm°C

                   #Check_Fig_here.

R(0) = Resistance of the material at 0°C
R(t) = Resistance of the material at t°C

Increase in Resistance depends upon
¡) initial resistance
¡¡) rise in tempt.
¡¡¡) on thr nature of the material.

#Alpha signs denotes temperature co-efficient of resistance normally.

wiki source :
Alpha (uppercase Α , lowercase α; Ancient Greek :
άλφα, álpha , modern pronunciation álfa ) is the
first letter of the Greek alphabet . In the system
of Greek numerals it has a value of 1. [dont forget to like, follow and support facebook.com/thecurrentblogelectrical for more]

α=[ dR/ R(0) ]x t
where dR = R(t) - R(0)

Theoretically, at -t tempt., the resistance should be vanished, but in actual at-234.5°C (easy to remember,look again), it never meet zero, it departs from a straight line at very low tempt.
see figure.
So The second part now.

Question is, Why does electrical resistance increase as tempt. increases?
- Resistance of the conductor changes with change in size of the conductor as well as temperature.

Some says, as tempt. increases, the dimension of the conductor will expands or contracts and that is the reason behind change of resistance in material. It is actually misconception.
lets read! Those material,about which, we are talking in this post are classified into two groups
1. Resistance increases with increase in temperature.
2. Resistance decreases with increase in tempt.
Most of the metals are belongs to the the first one and insulators are from second.
The reasons for these changes can be explained by considering the flow of current(actually electron) through that material. Electron are negatively charged particles and will be attracted by positive atoms and repelled by negative charged electrons. So when a electric potential is applied, the free electrons tends to flow into the material and start to flow in time. Now Temperature is increased.
The effect of increase in temperature in material is to make the atoms vibrate and vibrate violently as tempt increases more. In a conductor which already has large amount of electron will make collision between electrons and vibrated atom. As a result, some kinetic energy of electron may fall and that vibration [ dont forget to like and follow and support us facebook.com/thecurrentblogelectrical for more] increases the resistance of that metal body.
Whereas, in insulators free electrons are quietly less than metal. Almost all the electrons are tightly bound within their particular atom. Increase in tempt. sufficiently vibrates the atoms and enough to actually shake some of the their captive electrons free.
So the resistance of Insulator material falls due to increase in tempt.
I have a question for you here.
What happen to electrolyte when tempt. increase? tell us in comment section.
P.S.
In a material where the resistance increases with an increase in tempt., the material is said to have a POSITIVE TEMPERATURE COEFFICIENT( e.g. Copper Cu).
When resistance decreases with an increase in tempt., the material is said to have a NEGATIVE TEMPERATURE COEFFICIENT(e.g. Semi-Conductors).