Final answer:
The electric force between two charged particles is reduced by a factor of 3 when one particle's charge is reduced by a factor of 3, according to Coulomb's law.
Step-by-step explanation:
If the charge of one of two particles is reduced by a factor of 3, the electric force between them according to Coulomb's law will also reduce by a factor of 3. Coulomb's law states that the force between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them. Therefore, changing one charge will directly affect the force.
When one charge reduces to one third of its original value, the new force becomes one third of the original force, because the force is directly proportional to the charges. Hence, if one charge is reduced by a factor of 3, the electric force between the two particles is reduced by a factor of 3. The correct answer is A. It is reduced by a factor of 3.