Consider again the circuit whose total resistance we have calculated. What is the current
through each resistor? What is the power dissipated in each resistor?WHAT IS THE CURRENT RUNNING THROUGH EACH RESISTOR?
We know that resistors in series do not affect the current, so the current through is the
same as the total current running through the circuit. Knowing the total resistance of the
circuit and the voltage drop through the circuit, we can calculate the circuit’s total current
by means of Ohm’s Law:
Therefore, the current through is 3 A.
But be careful before you calculate the current through and : the voltage drop
across these resistors is not the total voltage drop of 30 V. The sum of the voltage drops
across and the two resistors in parallel is 30 V, so the voltage drop across just the
resistors in parallel is less than 30 V.
If we treat the resistors in parallel as a single equivalent resistor of 6 , we can calculate
the voltage drop across the resistors by means of Ohm’s Law:
Now, recalling that current is divided unevenly between the branches of a set of resistors
in parallel, we can calculate the current through and in the familiar way: