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A student writes for a loop: 'The sum of all voltage magnitudes in a loop is always zero.' Why is this statement incorrect?
ABecause only current, not voltage, can be summed in a loop
BBecause the algebraic sum of voltages is zero, so sign and direction matter
CBecause voltages in a loop are never added
DBecause the source voltage must always be ignored
Answer & Solution
Correct answer: B. Because the algebraic sum of voltages is zero, so sign and direction matter
KVL uses an algebraic sum, not a sum of magnitudes. Voltage rises and drops have signs determined by the chosen traversal direction and polarity, so direction matters. If you simply add magnitudes, you lose the cancellation that makes the loop sum zero.