Final answer:
Adding a dielectric to a capacitor decreases the potential difference between the plates as it increases the capacitance. This effect is observed if the capacitor is disconnected from a voltage source after being charged. Therefore, the correct answer is B) Decrease.
Step-by-step explanation:
When you insert a dielectric between the plates of a capacitor, the potential difference between the plates will decrease. This happens because a dielectric material increases the capacitor's ability to store charge at the same voltage, which is to say, it increases the capacitance.
Hence, if the voltage remains constant, the potential difference will not change. However, for a charged capacitor disconnected from any voltage source, the insertion of a dielectric will reduce the potential difference.
When a dielectric is inserted between the plates of a capacitor, it increases the capacitance, which is the ability of the capacitor to store charge.
As a result, the potential difference, or voltage, across the plates decreases. This can be explained by the equation C = Q/V, where C is the capacitance, Q is the charge stored on the capacitor, and V is the potential difference across the plates.