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GCSE Physics · key term
A voltage that keeps the same polarity, so one terminal remains positive relative to the other.
Used by Edexcel
Specification 10.33 · Paper 2
Revise: DC vs AC VoltageA direct voltage keeps the same polarity: the same terminal remains positive relative to the other. A cell or battery normally provides a direct voltage. For an ideal steady battery, a graph of voltage against time is a horizontal line above or below zero because the voltage has a constant value and does not reverse polarity.
On a voltage–time graph, identify a direct voltage by its unchanged polarity: the trace stays on one side of 0 V. An alternating voltage crosses 0 V and takes both positive and negative values.
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