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EMF and PD
The electromotive force or EMF of a power supply is the work done on (or energy transferred to) one
unit of charge passing through the power supply.
The potential difference or PD of a component in a circuit is the work done by (or energy…
Measuring EMF and internal resistance graphs
If you connect the power supply to a variable resistor then you can use the variable resistor to alter the
current drawn from the power supply.
E.g. E r
The terminal PD is the EMF minus the lost…
A very high voltage power supply (also known as an extra high tension or EHT supply) will have a large
resistor deliberately placed inside the supply to increase the internal resistance (usually to a value of
thousands of ohms).
The internal resistor will limit the maximum current that can be…