In an electric circuit, two elements that commonly cause an electric potential drop are resistors and diodes. These components work by dissipating electrical energy in the form of heat or through a barrier allowing current to flow in one direction only. This dissipation results in a reduction of voltage across the component.
On the other hand, an element that causes an electric potential gain is a battery or any type of power source. Batteries convert stored chemical energy into electrical energy, thereby increasing the voltage available in the circuit and allowing current to flow towards other components.
To summarize, resistors and diodes are responsible for potential drops, while batteries provide potential gains.