Physics
Mixing Up Series and Parallel Circuits
Students add resistor values in every circuit, even when the resistors are connected in parallel.
Quick check
Why students make it
Series circuits look simpler because charge has one path, so adding resistances feels like the default rule. In parallel circuits, extra branches actually give charge more paths, so the equivalent resistance gets smaller.
The rule done right
In series, resistances add directly, so . In parallel, reciprocals add, so .
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