- From : Kimball, Arthur Lalane, A College Text-Book
of Physics, 3rd ed., H. Holt and Co., New York (1923) pp.473-4.
- © Copyright 1998 R. Paselk
- 694. Ammeters.
- An ammeter is some form of galvanometer or electrodynamometer
graduated so that the current strength in ampéres may
be directly read from the scale. A form of ammeter much used
for direct currents is shown in figure 401. It consists of a
sensitive moving-coil galvanometer
in which the coil instead of being suspended is mounted in jeweled
bearings and is held in equilibrium by two non-magnetic spiral
springs which also serve as conductors for the current. The main
current passes through a strip of metal (called a shunt) having
very small resistance, only a minute portion of.the current passing
through the delicate movable coil. But the current in the movable
coil is always the same proportional part of the whole current,
and therefore the scale over which the pointer moves may be so
graduated as to show directly the number of ampéres in
the total current. An instrument of this type has the advantage
of having a very small resistance.
- © R. Paselk
- Last modified 22 July 2000