Electric Circuits - Mission EC8 Detailed Help

Three identical light bulbs are connected to a battery as shown below. P, Q, X, Y and Z represent locations along the circuit. At which location will the current be the same as at X (or at Y or at Z or at ...)?


 
Current in Parallel Circuits:
Parallel circuits are characterized by branching locations. At each branching location, the current is divided into separate pathways. The overall current approaching the branch is equal to the sum of the current values in each individual branch. This can be expressed in equation form as:     
Itot= I1+ I2+ I3+ ...

where Itot is the current outside the branches (and through the battery) and I1, I2 and I3 are the current values in the individual resistors.

 
This question asks you to make comparisons of the current at various locations within a parallel circuit. There are three separate branches containing identical resistors. Locations Y and Z represent locations within a single branch. Locations P and X represent locations outside of the branches. Location Q represents a location that channels current to two different branches. The current in each individual branch is identical since the branches have the same voltage drops and the same resistance values. If the current at location P were 6 amperes, then each branch would encounter 2 amperes of current. At the branching location immediately after point P, the current would be divided into two parts. There would be 2 amperes channeled to the first resistor and 4 amperes channeled to point Q in order to feed the remaining two resistors. The 4 amperes of current at point Q would then divide into two parts at the next branching location - with 2 amperes being channeled to each remaining branch. At location X, all three branch currents would meet together to form 6 amperes of current. Using sample numbers such as this should assist in analyzing the current in the circuit and answering the question.


 

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