An uncharged metal
container (the "ice pail") is connected to
an electroscope.
A
charged metal sphere is lowered into the container.
The
electroscope indicates an induced
charge on the container. The charge on the
inside of the container is
opposite to the charge on the sphere. On
the outside it is the same as
the charge on the sphere.
If the sphere is moved
about inside the container, the "leaf" of
the electroscope remains
in the same position
When the
sphere is removed, the electroscope returns
to its original state.
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