How does adding a third parallel capacitor affect the voltage drop across capacitor 1 and the charge stored on it?

When a third capacitor is added in parallel to a circuit with other capacitors, the voltage drop across each capacitor in that parallel configuration remains constant and equal to the voltage of the power source. In a parallel circuit, capacitors share the same voltage, and this fundamental characteristic means that adding another capacitor does not alter the voltage across any single capacitor, including capacitor 1.

In terms of charge, each capacitor stores charge proportional to its capacitance and the voltage across it, as described by the relation Q = C × V, where Q is the charge, C is the capacitance, and V is the voltage. Since the voltage remains unchanged when the additional capacitor is added, capacitor 1 will not see a change in charge stored on it. The charge stored only changes if either the voltage changes or the capacitance of capacitor 1 changes, neither of which occurs by simply adding another capacitor in parallel.

Thus, since both the voltage drop across capacitor 1 and the charge stored on it are unaffected by the addition of a third parallel capacitor, the correct conclusion is that nothing changes. This understanding is essential for analyzing parallel circuits in electrostatics.