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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.

Definition


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 .


Example

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