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Home Minds On Electric Circuits Mission EC8 Parallel Circuits Concepts Help Help 6

Mission EC8 Parallel Circuits Concepts

The Question

Which adjustments could be made to the circuit below that would increase (or decrease) the current at X (or at Z or in the battery)? List all that apply ...

Physics Rules

Equivalent Resistance in Parallel Circuits:
Parallel circuits are characterized by multiple pathways or branches through which charge flows. When additional resistors are placed within separate branches of a parallel circuit, additional pathways for charge flow are provided. Thus, the addition of more resistors (which also means additional pathways) has the effect of decreasing the overall resistance and increasing the overall current.

Physics Rules

Branch Currents in Parallel Circuits:
The current in an individual branch of a parallel circuit is dependent upon the voltage drop across the branch and the resistance of the resistor within the branch. The voltage drop across a branch in a parallel circuit is equal to the voltage rating of the battery. Thus, the current in a branch can be calculated as
 
 Ibranch= ∆Vbattery/ Rbranch

Think About It

This question is a rather difficult question that asks you to predict the changes that would result in an increase in the current at a specified location within a parallel circuit. The location may be a location within a branch or a location outside of the branches.
 
Increasing the current in the battery and at locations outside of the branches can be done in a variety of ways. The current in the battery is directly related to the battery voltage and inversely related to the overall or equivalent resistance. Refer to the first Know the Law section.
 
Increasing the current in an individual branch could be done in one of two ways. The current in each individual branch is directly related to the battery voltage and inversely related to the resistance of the bulb in that branch. See the second Know the Law section.

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