Question

Two copper balls, each weighing 10g are kept in air 10 cm apart. If one electron from every 106 atoms is transferred from one ball to the other, the coulomb force between them is (atomic weight of copper is 63.5)

A
2.0×1010N

B
2.0×104N

C
2.0×108N

D
2.0×106N

Solution

The correct option is C 2.0×108N  Number of atoms in given mass =1063.5×6.02×1023 =9.48×1022 Transfer of electron between balls =9.48×1022106 =9.48×1016 Hence magnitude of charge gained by each ball. Q=9.48×1016×1.6×10−19=0.015C Force of attraction between the balls F=9×109×(0.015)2(0.1)2=2×108N.

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