Capacitance (C) is defined as the ratio of charge (q) to potential difference (V):
$C = \frac{q}{V}$
However, capacitance is primarily determined by the geometry of the capacitor (plate area, separation between plates, dielectric material). The charge (q) and potential difference (V) are related to the capacitance but do not determine it. A capacitor with a specific geometry will have a fixed capacitance.
AB is a part of an electrical circuit (see figure). The potential difference \(V_A - V_B\), at the instant when current \(i = 2\) A and is increasing at a rate of 1 amp/second is: