Lesson 32 The Electric Battery

To understand a battery, understand the process of making a metal. Begin with a positive ion, because it has a positive charge, it creates the potential energy of attraction for the missing electron. Place positive ions adjacent to one another. Add just enough electrons to make a neutral system and arrange in the form of a lattice to create a piece of metal. A positive test charge would detect no change in potential energy and therefore no force anywhere inside or outside the metal. A real electron inside the metal is acted on by all the ions and electrons except for itself, lending itself a net potential energy. If the electron is moved from one part of the metal to another, other electrons flow to replace it so it has the same potential energy everywhere. There is virtually no force preventing an electron from moving freely through the metal. Beyond the surface of the metal, there are no more ions or electrons to balance forces. So to push an electron outside of metal requires a powerful force, creating a real electric potential and leaving a net positive charge on the metal. The overall potential energy of a real electron drops sharply at the metals surface to a lower value that is the same everywhere inside.

The electrons of a metal also have kinetic energy, but not enough to escape. The amount of energy an electron would need to escape from a metal is known as the work function.

Volta developed the perpetual resevoir of electricity, or the electrophorous.

Galvani studied "animal electricity" using frog legs to which he discovered that nerve impulses which excite muscles into action are really electrical sigals which travel everywhere throughout the body.

Why is an electric impulse created when one metal touches another?

Each metal has a work function that keeps electrons from escaping. The work function of copper and zinc differ from one another by the electric potential IV. When two metals are brought into contact the barrier at the interface vanishes. The electrons are free to flow into the metal where they have lowered total energy. As electrons flow, the metal they leave becomes positively charged and the one they enter becomes negatively charged. This creates an electrostatic potential difference that balance the energy difference. The flow stops. If the metals are separated, each has a net electric charge and an electrostatic potential difference between them.

Volta did not have the luxury of the electron, so he developed the voltaic pile.

Suppose two different metals electrically charged from contact are placed in an electrolite, the metal has extra electrons, attracts positive ions from the solution whenever positive ions touch the surface they can extract excess electrons from the metal. Meanwhle, the other metal which lacks electrons attracts negative ions when negative ions reach the surface, the missing electrons can be replaced. So the electrolite drives the metals back to an electrically neutral position. If they were to make direct contact, a new surge of electrons would flow because of their difference in work fucnctions. Now, because of the electrolite, the surge does not cease. Electrons continue to flow from one metal to the other and they are continually replaced by the ions in the solution. Until there is no more chemical energy. This is known as the battery.