Batteries Chapter 2: Section 2

ENERGY Energy can be transformed from one form into another Batteries store chemical energy  Chemical Energy is energy stored in chemical compounds. Batteries transform chemical energy into electrical energy

LUIGI GALVANI In 1780 Galvani was studying the anatomy of a frog.  Used a brass hook to hold the frog’s leg muscle in place  When he touched the hook to an iron railing the frog’s leg twitched  He hypothesized there was some kind of “animal electricity” present in living tissue.

ALESSANDRO VOLTA Volta later disproved Galvani’s observation Volta hypothesize what Galvani observed was a chemical reaction between the iron railing, the brass hook and the salty fluids in the frog’s leg.  Chemical Reaction is a process in which substances change into new substances with different properties  Example of a chemical reaction –

THE FIRST BATTERY Volta tested his hypothesis:  He put a piece of soaked salt paper in between a piece of zinc and a piece of silver  He connected wires to the silver and zinc and found current was produced  He repeated the layers: zinc, paper, silver, zinc, paper, silver.. And so on. The more he did, the bigger the current. Volta built the first electric battery in the 1800’s

ELECTROCHEMICAL CELLS In Volta’s setup each pair of zinc, paper, and silver acted as an electrochemical cell In electrochemical cell is a device that converts chemical energy into electrical energy  Has two metal Electrodes  Electrodes are im- mersed in electrolyte  Electrolyte is a sub- stance that conducts electric currents.

A SIMPLE CELL The part of an electrode above the surface of the electrolyte is called a terminal. Terminals are used to connect the cell to a circuit. Chemical reactions occur between the electrolyte and the electrodes in an electrochemical cell. These reactions cause one electrode to become negatively charged and the other electrode to become positively charged Because of the opposite charges there is a voltage between them (remember charges flow)

A SIMPLE CELL Therefore if terminals are connected to a wire, charges will flow from one terminal to another. Electrochemical cell produces the electric current in the wire. Charges flow back through the electrolyte to make a complete circuit.

BATTERIES A battery is a combination of two or more electrochemical cells in a series.  2 or more electrochemical cells are connected in series. This means the positive terminal of one end is connected to the negative terminal of the next.  Voltage of the battery is the sum of the voltage of the cells.

TYPES OF ELECTROCHEMICAL CELLS Wet Cells Dry Cells An electrochemical cell in which the electrolyte is a liquid is a wet cell. An electrochemical cell in which the electrolyte is a paste.