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I understand how series and parallel circuits are different and I understand how to calculate the resistance [etc] in a parallel circuit, but why is there LESS resistance when things are arranged in parallel [ie two 10 ohm bulbs]?.

V = I x R
Think in terms of the current flow. For a given voltage, if the current goes up the resistance must have gone down. If you provide one path the current is restricted to the one path. If you provide a second, equivalent path, twice as much current can flow. The current has increased, therefore the resistance must have decreased. In essence, resistance measures how BAD the path is for current flow. When there are two equivalent paths the paths are LESS bad.


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