Measuring Power
Power Rating of Resistors
Manufacturers supply resistors with different power ratings. In the low power resistor range, these ratings are;
0.25 Watt, 0.5 Watt, 1 Watt and 2 Watt.
A resistor must have a power rating high enough to dissipate the heat produced by the current flowing through it ( I2R ).
Some resistor types have the power rating marked on the body. In other cases it is the physical size of the resistor that determines its wattage. Carbon film resistor dimensions are illustrated below. Refer to Figure 4.
Power in a Series Circuit
The power dissipated by any resistor is given by, the voltage across that resistor multiplied by the current flowing through it.
