Cells and Batteries

Cells and Batteries•Electrons are involved in static charge –

we know!•How does this relate to electronic devices?•Electric circuits!▫A closed path along which electrons that are

powered by an energy source, can flow

Cells and Batteries•Most batteries used today are

similar to Alessandro Volta’s “Voltaic pile”

•Voltaic cells generate an electric current by chemical reactions between 2 different metals separated by a conducting solution

•Battery = a connection of 2 or more cells

•Clarification: a regular AA battery is technically a cell

Batteries•A battery is essentially a can full of chemicals

that produce electrons

•2 terminals (electrodes): +ve and –ve▫Made of different metals▫Immersed in electrolyte (solution or paste)

• If you connect a wire between electrodes, electrons will flow (from -ve end to +ve) as fast as they can▫Wears out the battery quickly▫Dangerous ▫Use a load

Batteries• Inside battery, a chemical

reaction produces ions▫Takes place at surface of

electrode

•Electrons travel through connecting wire to positive electrode▫Attracted to +ve electrode

•The -ve metal disintegrates slowly▫Limits the life of a cell

Types of CellsDry Wet

• Electrolyte is a paste• Uses zinc and carbon• Major advance came with

alkaline cells More expensive Last longer

• Electrolyte is a liquid• Most use sulfuric acid

Types of CellsDry

Wet

Types of Cells

•Primary – can be used only once•Secondary – can be recharged many times▫Electric current is passed in opposite

direction through cell Reverses the chemical reactions, restoring

cell to full capacity•Fuel cell – generates electricity through

chemical reactions of fuel that is stored outside the cell▫Eg. Hydrogen stored in a tank combined

with Oxygen

For Homework:

•Read pg 511-513

•Answer questions p. 513 #4, 5, 7