Resistance Characteristic
1. Power rating
• It specify the maximum power that can be handled by
the resistors.
• P= V X I .
• It is measured in watts. Resistance comes in 1/16 watts
to 300 watts.
• A resistance have input of 5 volt and current 1 Amp then
by the above formula P = 5 x 1 = 5 watts.
2. Tolerance:
• Tolerance is the percentage measure of the accuracy of a
resistors from its preferred value.
• 100 Ω with tolerance 10% means it will 100 + 10%.
i.e. resistance of that resistors by 90 Ω to 110 Ω
3. Temperature Co-efficient :
• Temp co-efficient of resistance is the measure of change
in electrical resistance of the resistors per degree of
temperature.
• It is usually measured in PPM/0c (Parts per million per
degree centigrade)
• If a resistor of 50 Ω TCR 20 PPM/0c and if temperature is
raised to 25oc
then
(20/1000000) x 50 x 25 = 0.025
50 Ω = 50.025 Ω .
4.Noise :
• The vibrations of the electrons cause an electric signal
across the terminals of the component. This electric
signal is called noise or thermal noise.
5. Frequency Response:
• The frequency response of a resistors is the frequencies
the resistors will work as a pure registers without any
significant effects associated with other component.
• Frequency response of wire wound resistors is high so, it
is used in high power application.
6. Stability :
• Stability defines the long term variations of the
resistance. After a long duration of electric load,
resistance value will not vary much.
Resistance
+
-
r1 r2 r3.
