Ammeter in Series
An ammeter (A) is placed in series to measure current. All of the current in this circuit flows through the meter. The ammeter would have the same reading if located between points d and e or between points f and a, as it does in the position shown. (Note that the script capital E stands for EMF, and r stands for the internal resistance of the source of potential difference. )
Source
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"OpenStax College, College Physics. October 25, 2012."
http://cnx.org/content/m42360/latest/?collection=col11406/latest
OpenStax CNX
CC BY 3.0.