The experimental galvanometer described here can detect currents as low
as few microamperes and uses unusual parts. This galvanometer operates
as common commercial galvanometers found in multi meters and several other
analog instruments.
One purpose of this experiment can be to demonstrate that there is a magnetic field around a coil that that is carrying electricity (Oersted Experiment).
The operating principle is very simple to understand: an electric current flowing across a coil (or a wire) produces a magnetic field. The field can act on a
mobile magnetic metal piece, such as a compass pointer or a blade, as shown
in the figures herein. The compass or blade movement indicates the presence of a current.
Figure I shows the two basic versions of the experimental galvanometer,
using a common compass and using a blade. ls very importanto observe
the correct path for the current flow in the coil. The coil should be wired exactly as shown in the figure.
ln Figure 2 we have a circuit to operate the galvanometer. The resistor can
range from 100 to 100,000 ohms. The higher the resistor, the more sensitive
is the galvanometer. Experiment to find the highest resistor value that can
cause the pointer to move.
The coil is made with 50 to 200 turns of No. 28 to 32 wire on a paper form.
Number of turns determines sensitivity. The higher the number of turns, the
more sensitive is the galvanometer.
Gurrents as low as a few microamperes can be detected with a carefully
made prototype.
Parts EG
L1 - Coil
X1 -Compass or Blade
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