Question

How do you make an insulated metal sphere has a net positive charge with a negatively charged rod?

If the rod touches the sphere, the sphere will have negative charge. If I connect sphere to ground, bring the rod near the sphere, negative charge will go to ground, then I have a positively charged sphere?
is this correct and if so could you please explain ..
thanks

Answer 1

If the rod touches the sphere is charging by induction. The rod has excess negative charge (that makes it negative), when they touch, the electrons leave the negative rod in favour of the neutral sphere, the electrons spread about the sphere uniformly. This leaves the rod less negatively charged, and the sphere negatively charged.
If the rod is brought near the sphere, this is called charging by induction. The positive charge is attracted towards it and the negative is repelled. They are now on opposite sides. When connected to the ground, the repelled negative charge leaves the sphere. The sphere now has excess positive charge and is thus positively charged
There is an animation here: http://www.physicsclassroom.com/mmedia/estatics/isop.cfm

Answer 2

thankkks
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