1) Batteries work by using a chemical reaction to create a difference in electrolytic potential between two terminals placed in an electrolyte. Ions are attracted to the opposite terminal, creating a flow of electricity. 2) Primary cells cannot be recharged, while secondary cells can be recharged by applying an external voltage to reverse the chemical reaction. 3) There is a potential difference (p.d.) or voltage across any component that converts electrical energy to other forms like heat or light. P.D. is measured in volts and represents the electrical potential energy lost per coulomb passing between two points.