Tuesday, 19 December 2017

resistance - Wattage calculation for resistors in series


I need the formula for calculating resistor wattage when the resistors are in series. For example, say I have 3 1/4 watt 10 ohm resistors in series. What is the potential power dissipation for the entire circuit?



Answer



Since resistors are in series, the current will be the same throughout the chain. Assuming that the voltage V across the string of resistors is constant, you can calculate the current \$I={V \over R_1+R_2 +R_3+ ...}\$. Power dissipated on each of the resistors: \$P_i=I^2R_i\$. If \$P_i\$ is less than the power rating of the resistor, it should dissipate the power without burning.


A string of N identical resistors in series each rated for P watts can dissipate \$NP\$ watts.


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