Final answer:
The magnitudes of the electric forces on two charged beads are equal and opposite. When two charged spheres touch and separate, each one receives half of the total charge, resulting in both spheres having equal charges of -4 nC.
Step-by-step explanation:
When two tiny beads with charges -20µC (bead A) and +5µC (bead B) are 5 cm apart, the magnitudes of the electric forces on these beads are equal. According to Coulomb's Law, the force experienced due to electric charges is equal in magnitude and opposite in direction, based on Newton's third law of motion. Since there are no other charges or fields present, the only forces acting on the beads are due to each other.
For the scenario involving two charged metal conducting spheres, when they touch, charges redistribute equally because they are identical. If spheres A and B have -5 nC and -3 nC charges respectively, they have a total charge of -8 nC. After touching and separating, each sphere will carry half of the total charge, which is -4 nC per sphere.