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Home Minds On Electric Circuits Mission EC8 Parallel Circuits Concepts Help Help 7

Mission EC8 Parallel Circuits Concepts

The Question

A 12-V battery and a 12-ohm resistor are connected as shown in circuit X below. Two 12-ohm resistors are connected as shown in circuit Y. The current in the battery in circuit X is ____ that in the battery in circuit Y.

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.

Think About It

This question asks you to make a comparison of the current in a battery in two different circuits. Circuit X contains a single resistor. Circuit Y contains two or more resistors placed within parallel branches. For each circuit, the current in the battery is the ratio of the battery voltage to the overall or equivalent resistance. That is Ibattery= ∆Vbattery/ Requivalent

Each circuit is equipped with the same battery voltage. So the determining factor that would effect the current is the overall resistance. For circuit X, the overall resistance is simply the resistance of the single resistor. For circuit Y, the addition of more resistors in separate branches has the affect of reducing the overall resistance and increasing the overall current. See Know the Law section.

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