A drop with a charge of -4 e has joined a water drop with an electric charge of +3 e.

A drop with a charge of -4 e has joined a water drop with an electric charge of +3 e. What is the electric charge of the combined drop?

To solve this problem, remember that according to the second law of interaction of electric charges, unlike charges are attracted to each other, therefore, therefore, two drops are combined into one. Now we need to find the electric charge of the combined drop and for this we apply the law of conservation of charges: q1 + q2 + q3 + … = const. Let’s add our two charges and get: q1 + q2 = + 3e + (-4e) = -1e