Student Question

# Why is potential difference the same in a parallel combination?

## Expert Answers

The work done by the electric field to move a unit of electrical charge between two points in a circuit represents the potential difference between these points.

This relationship is expressed in the following equation:

ΔV = W/q

On the other hand we have, that the electric field is a conservative field; This means that the work carried out by the field, between two points, does not depend on the path followed by the electric charge between these points.

When connecting several components between two points in a circuit (parallel connection), the electric charge moves through several paths between these two points but the work performed by the field, or the potential difference between the points, is the same for all paths. So in this type of connection, the potential difference is the same for all components.

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It has to do with the way the diagram is set up.  The wire that is used has very little resistance to it, so the electrical current will flow freely from high potential to low potential.  When you place an electrical component to be powered, say, two light bulbs in two lamps, the resistance to each appliance is the same.  The current that flows through the first part of the parallel loop will be the same that flows through the second parallel loop.  The sum of the two currents will equal the total current flowing through that circuit.  The nice part of this type of wiring is if the first lamp goes out, the second lamp will keep going, as long as the filament in the bulb doesn't burn out.  This is why most houses are wired with parallel wiring scheme, to prevent an electrical overload, which would be a fire hazzard.  The other type of wiring scheme is a series circuit, where several outlets would be wired together.  If one of the appliances burns out, this causes the electrical supply to the other outlets to halt.  It has the same effect of tripping a circuit breaker in the fuse box, where several outlets are wired together on the same circuit.

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