- 2071 Shrawan · 4 marks
Potential difference versus emf
Short answer
EMF is energy supplied by source per coulomb, exists without current; potential difference is energy used per coulomb between two points, exists when current flows. In a source, V = E − I·r. Unit is volt.
What is the difference between the potential difference and electromotive force?
| Point | EMF (E) | Potential difference (V) |
|---|---|---|
| Meaning | Energy given by the source to each coulomb of charge | Energy used by each coulomb between two points |
| Where it exists | Source (cell, generator) | Across any element or between any two points |
| Cause | Chemical, magnetic or other energy conversion | Current flowing through a resistance |
| Circuit condition | Exists even when no current flows | Exists only when current flows (or charge is separated) |
| Value | Greater than or equal to the terminal voltage | Less than EMF in a source with load |
| Relation | E = V + I·r (r = internal resistance) | V = E − I·r, or V = I·R |
| Unit | Volt | Volt |
EMF is the cause that drives current; potential difference is its effect across a circuit element. When a source supplies no current, its terminal potential difference equals its EMF.
✓ Answer checked by Claude Opus 5.5 (high effort)
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