SCEN103: Hoaxes and Urban Legends

Silicon, Circuits, and the Digital Revolution

Voltmeters and Ammeters

An ammeter measures current through a circuit element;
-- therefore it must be connected in series with it.
An ammeter should have a much lower resistance than the other elements in the circuit;
-- otherwise current may change significantly.
Consider effective resistance.

A voltmeter measures voltage across a circuit element;
-- therefore it must be connected in parallel with it.
A voltmeter should have a much higher resistance than the element in parallel;
-- otherwise voltage will change significantly.
Again, consider effective resistance.

Comments, suggestions, or requests to ghw@udel.edu.
"http://www.physics.udel.edu/~watson/scen103/colloq2000/meters.html"
Last updated March 16, 2000.
© George Watson, Univ. of Delaware, 2000.

	An ammeter measures current through a circuit element; -- therefore it must be connected in series with it. An ammeter should have a much lower resistance than the other elements in the circuit; -- otherwise current may change significantly. Consider effective resistance.
	A voltmeter measures voltage across a circuit element; -- therefore it must be connected in parallel with it. A voltmeter should have a much higher resistance than the element in parallel; -- otherwise voltage will change significantly. Again, consider effective resistance.