# A sphere with radius R=20mm is loaded till a potential V=-2KV. Find the weight of all electrons transferred to sphere, in the loading process.

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The number of electrons and their weight:

N=Q/(-e),m=N*me=[Q/(-e)]*me (1)

We ahve to say it again that inside a sphere , the field and the potential are as the load would be concentrated in the center of sphere.

V=Q/(4*pi*epsilon*r)

E= Q/(4*pi*epsilon*r^2)

In particular, the potential of the sphere itself:

V=Q/(4*pi*epsilon*R), R=r

We'll draw out the load from this formula and we'll introduce it in (1):

Q=4*pi*epsilon*R*V,

m=(4*pi*epsilon*R*V*me)/(-e)=25