Influence of Temperature on ResistanceThe electric current is more than army of electrons which stimulates the atoms in a conductor. If a material (conductor) is heated, the atoms vibrate. This will make the free electrons to collide with the atoms. This creates more resistance in the movement of electrons through the conductor. The resistance will be more with rise in temperature. This feature is known as the temperature coefficient of resistance. It is defined as the change in resistance per degree rise of temperature for every ohm of resistance. It is denoted by the symbol “alpha” (α). All the conductors have their specific temperature coefficient at 20 degree Celsius. For pure metals, temperature coefficient is positive that means their resistance will increase with increase in temperature. This is referred as positive temperature coefficient of resistance. While for some elements temperature coefficient is negative that means their resistance will decrease on increasing the temperature which is known as negative temperature coefficient of resistance. For some very good conductors, the temperature coefficient is nearly zero, which means their resistance doesn’t change a lot with a change in temperature. This type of metals is generally used for making precision resistors. The change in resistance of resistors other than 20 degree Celsius can be given by this formula.
R=R0 [1+α(T-T0 )]
∴R=21.6164ΩTherefore, the value of resistance changed by 1.6Ω. This can bring a huge difference in circuit. To observe this difference lets us assume this resistor is connected to 12Vand we need to figure out the current. Then, if we do not consider effect of temperature, then current would be
I = 12/20 = 0.6AAnd if we calculate keeping in mind the effects of temperature, current would be
I = 12/21.6164 = 0.55AYou can observe the difference we are getting. This difference can sometimes mislead and thus we have to keep in mind the effect of temperature on the value of resistance. The below table shows the temperature coefficient of resistance for various metals.