Question

Two small identical conducting spheres are placed with their centers 0.50 m apart. One is given a charge of 12 ✕ 10⁻⁹ C, the other a charge of −20 ✕ 10⁻⁹ C.

(a) Find the electrostatic force exerted on one sphere by the other.

magnitude	N
direction	---Select--- attractive repulsive

(b) The spheres are connected by a conducting wire. Find the electrostatic force between the two after equilibrium is reached, where both spheres have the same charge.

magnitude	N
direction	---Select--- attractive repulsive

Answer 1

$q_{1}=12*10^{-9}C$

$q_{2}=-20*10^{-9}C$

$d=0.5m$

(a) $F=kq_{1}q_{2}/d^{2}$

$F=9*10^{9}*12*10^{-9}C*20*10^{-9}C/(0.5m)^{2}$

${\color{Red} F=8.64*10^{-6}N}$

Since the charge are unlike ,Force is Attractive

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(b)After spheres reaches equilibrium ,charges change

$q_{1}=q_{2}=(12*10^{-9}C-20*10^{-9}C)/2 =-4*10^{-9}C$

$F=kq_{1}q_{2}/d^{2}$

$F=9*10^{9}*4*10^{-9}C*4*10^{-9}C/(0.5m)^{2}$

${\color{Red} F=5.76*10^{-7}N}$

Since the charge are like(same),Force is Repulsive.

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