ELECTRICITYBatteries

Chapter 2:Section 2

ENERGYEnergy can be transformed from one form

into anotherBatteries store chemical energy

Chemical Energy is energy stored in chemical compounds.

Batteries transform chemical energy into electrical energy

LUIGI GALVANIIn 1780 Galvani was studying the anatomy of

a frog.Used a brass hook to hold the frog’s leg muscle

in placeWhen he touched the hook to an iron railing

the frog’s leg twitchedHe hypothesized there was some kind of

“animal electricity” present in living tissue.

ALESSANDRO VOLTAVolta later disproved Galvani’s observationVolta 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 –http://www.youtube.com/watch?v=2zgYQgQC9II

THE FIRST BATTERYVolta 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 CELLSIn Volta’s setup each pair of zinc, paper, and

silver acted as an electrochemical cellIn electrochemical cell is a device that

converts chemical energy into electrical energy Has two metalElectrodes Electrodes are im-mersed in electrolyte Electrolyte is a sub-stance that conducts electric currents.

A SIMPLE CELLThe 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 CELLTherefore 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.

BATTERIESA 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 CELLSWet 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.