| Electromotive Force (EMF) | Potential Difference (PD) |
|---|---|
| 1. Work done by a source to move a unit charge once around the entire complete circuit. | 1. Work done in moving a unit charge from one specific point to another in a circuit . |
| 2. Maximum voltage across the terminals of a source when no current flows (open circuit). | 2. Voltage measured between any two points when current is flowing (closed circuit). |
| 3. Exists even when the circuit is open/disconnected. | 3. Exists only when the circuit is closed and current flows. |
| 4. Originates from non-electrostatic sources (like chemical reactions in a cell). | 4. Originates from the electrostatic field set up by charge buildup across terminals. |
| 5. It is the **cause**. Applying an EMF creates a potential difference. | 5. It is the **effect** produced by the EMF. |
| 6. Equal to the sum of potential drops across all components, including internal resistance. | 6. Measured across individual components; each element has its own potential drop. |
| 7. Larger than the potential difference across any single component in the circuit. | 7. Always less than the overall EMF during circuit discharge. |
| 8. Independent of external resistance in the circuit. | 8. Depends directly on external resistance and current ($V = IR$). |
Difference between Electromotive Force (EMF) and Potential Difference (PD)
Difference between EMF vs. Potential Difference
