Power Dissipation in Resistors

Any resistor in a circuit that has a voltage drop across it dissipates electrical power. This electrical power is converted into heat energy hence all resistors have a power rating. This is the maximum power that can be dissipated from the resistor without it burning out. The rate of conversion is the power of dissipation.


Power Dissipated in a resistor

Using the formula for electrical power: . but and thus substituting in the equation for electrical power . This also works substituting , giving .


Calculate the power dissipated in a 10k resistor with a 5mA current through the resistor.

Using .
p = (5*10-3)2 * 10 * 103
p = 250mW.
i.e. The power dissipated in the resistor is 250mW.

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Mark Whiteley 2002