Difference between revisions of "Electromotive Force"
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The [[Terminal Voltage|terminal voltage]] of an [[Electrical Cell|electrical cell]] or [[battery]] is related to '''emf''' by the following formula: | The [[Terminal Voltage|terminal voltage]] of an [[Electrical Cell|electrical cell]] or [[battery]] is related to '''emf''' by the following formula: | ||
| − | *<math>𝑉= | + | *<math>𝑉=\varepsilon−𝐼𝑟</math> |
Where: | Where: | ||
*𝑉 is the [[Terminal voltage|terminal voltage]] | *𝑉 is the [[Terminal voltage|terminal voltage]] | ||
*𝐼 is the [[Electrical Current|current]] through between the terminals | *𝐼 is the [[Electrical Current|current]] through between the terminals | ||
*𝑟 is the [[Internal Resistance|internal resistance]] of the [[Power Supply|power supply]] | *𝑟 is the [[Internal Resistance|internal resistance]] of the [[Power Supply|power supply]] | ||
Latest revision as of 10:37, 28 May 2024
Key Stage 5
Meaning
Electromotive force (emf) is the amount of work produced per unit charge by a source of electric power.
About Electromotive Force (emf)
- Emf is given by the symbol \(\varepsilon\)
- Emf is measured in volts (V).
- Emf is not actually a force, but a potential difference that drives current around a circuit.
- In a circuit, the emf is equal to the potential difference across the terminals of the power source when no current is flowing.
- The internal resistance of the power source causes the terminal voltage to be less than the emf when current is flowing.
Formulae
The electromotive force is given by the formula:
- \(\varepsilon=\frac{𝑊}{𝑄}\)
Where:
The terminal voltage of an electrical cell or battery is related to emf by the following formula:
- \(𝑉=\varepsilon−𝐼𝑟\)
Where:
- 𝑉 is the terminal voltage
- 𝐼 is the current through between the terminals
- 𝑟 is the internal resistance of the power supply