Calculating E.m.f (OCR A Level Physics): Revision Note
Calculating E.m.f
The e.m.f ε is defined by the equation:
![EMF equation, downloadable AS & A Level Physics revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2021/04/5.4.1-EMF-equation.png)
E.m.f can therefore be defined as the total, or maximum, voltage available to the circuit
Worked Example
A battery of e.m.f 7.3 V and internal resistance r of 0.3 Ω is connected in series with a resistor of resistance 9.5 Ω.
![WE - internal resistance question image, downloadable AS & A Level Physics revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2021/04/WE-internal-resistance-question-image.png)
Determine:
a) The current in the circuit
b) Lost volts from the battery
Answer:
![Worked example internal resistance (2), downloadable AS & A Level Physics revision notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2021/07/10.1.1.5-Worked-example-internal-resistance-2_2.png)
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