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Unit 1: Thermal, nuclear and electrical physics

Quick questions on Series and parallel circuits and Kirchhoff's laws (QCE Physics Unit 1)

3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is adding parallel resistors directly?
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$1/R$ values add, not $R$ values. Two $6\,\Omega$ resistors in parallel give $3\,\Omega$, not $12\,\Omega$.
What is forgetting that parallel branches have the same voltage?
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This is the most useful single fact: at any parallel node, $V$ is common.
What is applying KVL with the wrong signs?
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Going around a loop, voltage drops across resistors in the direction of current flow are negative; battery EMFs going from negative to positive terminal are positive. Pick a direction and stick with it.

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