Answer to Question #258678 in Electricity and Magnetism for zher

Question

3. A metal banana-shaped earring has a net charge of -2.0 µC while a metal apple-shaped earring has a net charge of 8.0 uC. The earrings are 3.0 m apart. (A) What is the electric force between the two earrings? Is it attractive or repulsive? (B) The two earrings are brought together, touching one another for a few seconds, after which the earrings are once again placed 3.0 m apart. What is the electric force between the two earrings now? Is it attractive or repulsive?

Answer 1

1)

$F_1=\frac{k|q_1||q_2|}{r^2}=16~mN,$

$q_1q_2<0$ – attractive,

2)

$q=\frac{q_1+q_2}2=3~\mu C,$

$F_2=\frac{kq^2}{r^2}=9~mN,$

$q^2>0$ –repulsive.