Voltmeter and EMF
Voltmeter
A voltmeter is an instrument for measuring the potential difference between two points in an electric circuit.
The symbol for a voltmeter is:
A voltmeter
EMF
When you measure the potential difference across (or between) the terminals of a battery that is not in a complete circuit you are measuring the emf of the battery. This is the maximum amount of work per coulomb of charge the battery can do to drive charge from one terminal, through the circuit, to the other terminal.
Did You Know?
The volt is named after the Italian physicist Alessandro Volta (1745–1827).
Electrical potential difference is also called voltage.
When you measure the potential difference across (or between) the terminals of a battery that is in a complete circuit you are measuring the terminal potential difference of the battery. Although this is measured in volts it is not identical to the emf. The difference will be the work done to drive charge through the battery.
Batteries
Photography by scalespeeder on Flickr.com
One lead of the voltmeter is connected to one end of the battery and the other lead is connected to the opposite end. The voltmeter may also be used to measure the voltage across a resistor or any other component of a circuit but must be connected in parallel.
This lesson is part of:
Electric Circuits