Cargas Electricas

Chapter 23. The Electric Force

Coulomb's Law
23-1. Two balls each having a charge of 3 C are separated by 20 mm. What is the force of repulsion between them?
; F = 202 N

23-2. Twopoint charges of -3 and +4 C are 12 mm apart in a vacuum. What is the electrostatic force between them?
; F = 750 N, attraction

23-3. An alpha particle consists of two protons (qe = 1.6 x10-19 C) and two neutrons (no charge). What is the repulsive force between two alpha particles separated by 2 nm?
q = 2(1.6 x 10-19 C) = 3.2 x 10-19 C
; F = 2.30 x 10-10 N
23-4. Assume thatthe radius of the electron's orbit around the proton in a hydrogen atom is approximately 5.2 x 10-11 m. What is the electrostatic force of attraction?
; F = 8.52 x 10-8 N
23-5. What is theseparation of two -4 C charges if the force of repulsion between them is 200 N?
; r = 26.8 mm
23-6. Two identical charges separated by 30 mm experience a repulsive force of 980 N. Whatis the magnitude of each charge?
; q = 9.90 C

*23-7. A 10 C charge and a -6 C charge are separated by 40 mm. What is the force between them. The spheres are placed in contact for afew moments and then separated again by 40 mm. What is the new force? Is it attractive or repulsive?
; F = 338 N, attraction
When spheres touch, 6 C of charge are neutralized,
leaving 4C to be shared by two spheres, or
+2 C on each sphere. Now they are again separated.
;
F = 5.62 N, repulsion

*23-8. Two point chargesinitially attract each other with a force of 600 N. If their separation is reduced to one-third of its original distance, what is the new force of attraction?
; r1 = 3 r2
F2 = 5400 N

TheResultant Electrostatic Force
23-9. A +60 C charge is placed 60 mm to the left of a +20 C charge. What is the resultant force on a -35 C charge placed midway between the two charges?...