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GCSE Physics · key term
Which of two terminals is at the higher potential; reversing the polarity reverses the sign of the measured voltage.
Used by Edexcel and OCR
Specification 10.33 · Paper 2
Revise: DC vs AC VoltageA voltage also has a polarity: one point can be at a higher potential than the other. If the connections of a voltage-measuring device are reversed, the reading changes sign.
Specification P8.2h · Paper 2 (Foundation), Paper 4 (Higher)
The direction of a potential difference between two points, identified by which point is at the higher potential.
Revise: AC vs DCPotential difference, often called voltage, exists between two points. Its polarity tells us which of those points is at the higher potential.
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.
Do not say merely that an alternating voltage “changes”. Its defining feature is that its polarity reverses repeatedly; a varying voltage that never reverses polarity is still direct.
Describe voltage, not just the shape of a graph: d.c. keeps the same polarity, whereas a.c. repeatedly reverses polarity.
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