Basic DC Theory BASIC DC CIRCUIT CALCULATIONSStep 3: Find the voltage across each component.V_{1} = IR_{1}V_{1} = (0.6 amps)(40 W)V_{1} = 24 voltsV_{2} = IR_{2}V_{2} = (0.6 amps)(60 W)V_{2} = 36 voltsV_{3} = IR_{3}V_{3} = (0.6 amps)(100 W)V_{3} = 60 voltsThe voltages of V_{1}, V_{2}, and V_{3} in Example 2 are known as "voltage drops" or "IR drops." Theireffect is to reduce the available voltage to be applied across the other circuit components. Thesum of the voltage drops in any series circuit is always equal to the applied voltage. We canverify our answer in Example 2 by using equation (2-4).V_{T}V_{1}V_{2}V_{3}120 volts24 volts36 volts60 volts120 volts120 voltsParallelCurrentsThe sum of the currents flowing through each branch of a parallel circuit is equal to the totalcurrent flow in the circuit. Using Ohm’s Law, the branch current for a three branch circuitequals the applied voltage divided by the resistance as shown in equations (2-6), (2-7), and (2-8).Branch 1: (2-6)I_{1}V_{1}R_{1}VR_{1}Branch 2: (2-7)I_{2}V_{2}R_{2}VR_{2}Branch 3: (2-8)I_{3}V_{2}R_{2}VR_{2}Example 1: Two resistors, each drawing 3A, and a third resistor, drawing 2A, are connectedin parallel across a 115 volt source (Figure 23). What is total current?Rev. 0 Page 29 ES-02

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