Internal resistance in cells and solar cells arises from different mechanisms. In traditional cells, resistance is primarily due to the electrolyte and the materials used in the electrodes, which can impede ion flow. In contrast, solar cells experience internal resistance related to the semiconductor properties, where the movement of electrons is influenced by quantum mechanics at the junctions of different materials. The conductivity in solar cells is affected by factors such as temperature, light intensity, and material quality. Understanding these differences is crucial for optimizing performance in both types of devices.