To demonstrate the separation of charges in two insulated spheres
ac insulated part
b insulated handles FIG. 20.3
1. Place two insulated spheres in contact (Fig. 20.3a). 2. Hold a negatively charged rod near one sphere (Fig. 20.3b). At this point, the positive charge is attracted to the negative rod and the negative charge in the other sphere is repelled.
3. Separate the spheres while keeping the rod in place (Fig. 20.3c). The spheres now have separate and opposite charges.
4. Remove the rod. You will find that the spheres are now oppositely charged by induction. To demonstrate the separation of charges in one insulated sphere
temporary charging by induction
permanent charging by induction
positively charged
metal sphere insulated part
ground ac d b FIG. 20.4
1. Take an uncharged insulated metal sphere (Fig. 20.4a) and then hold a negatively charged rod near to it so that the charge separates (Fig. 20.4b).
2. Earth the sphere; the electrons that are repelled by the negatively charged rod travel out of the sphere to ground (Fig. 20.4c). (This can be done by touching the sphere; the electrons travel through you.)
3. Remove the earth (your finger). 4. Remove the rod. The sphere is left positively charged by induction (Fig. 20.4d).
