Practice Coulomb's Law in Physics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
Coulomb's law gives the electric force between two point charges. The force gets larger when the charges are larger and gets smaller with the square.
Like gravity between masses, but for charges. Double the distance and the force drops to one quarter. Double either charge and the force doubles.
Example 1
mediumTwo charges q_1 = 3 \times 10^{-6} \text{ C} and q_2 = 5 \times 10^{-6} \text{ C} are separated by 0.2 \text{ m}. What is the electrostatic force between them? Use k = 9 \times 10^9 \text{ N m}^2/\text{C}^2.
Example 2
hardTwo identical charges experience a force of 0.1 \text{ N} when separated by 0.3 \text{ m}. What is the magnitude of each charge?
Example 3
mediumIf the distance between two charges is tripled, by what factor does the electrostatic force change?
Example 4
hardTwo charges q_1 = +4 \times 10^{-6} \text{ C} and q_2 = -2 \times 10^{-6} \text{ C} are separated by 0.1 \text{ m}. (a) Calculate the force between them. (b) Is the force attractive or repulsive? Use k = 9 \times 10^9 \text{ N m}^2/\text{C}^2.