During a laboratory demonstration of a Coulomb balance, two small metallised spheres are given electrostatic charges. Sphere A is charged to +12 nC+12\text{ nC}+12 nC and Sphere B is charged to −15 nC-15\text{ nC}−15 nC. The distance between their centres is adjusted to 6.0 cm.
What is the magnitude of the electrostatic force between the two spheres?
2.70×10−5 N2.70 \times 10^{-5}\text{ N}2.70×10−5 N
4.50×10−8 N4.50 \times 10^{-8}\text{ N}4.50×10−8 N
4.50×10−4 N4.50 \times 10^{-4}\text{ N}4.50×10−4 N
7.49×10−3 N7.49 \times 10^{-3}\text{ N}7.49×10−3 N
