Problem

Study the circuit depicted in Fig. 3.56, and explain (in terms of KCL) why the voltage labeled Vx must be zero.

FIGURE 3.56

Step-by-step solution

1. Step 1 of 2

   Consider the following circuit:

   

   Figure 1

   Comment

2. Step 2 of 2

   From the above circuit the current is flowing through the open circuit. So, there is no closed path for. Thus, the total current is flowing through  only.

   Therefore, .

   Kirchhoff’s current law states that the sum of the currents entering the junction is equal to the sum of the currents leaving the junction.

   Thus,

   

   Therefore the current, 

   Use Ohm’s law to determine .

   

   Thus, the voltage  must be .

   Comment