Cells and Batteries

1. Cells and Batteries

2. 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

3. 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

4. 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

5. 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

6. Types of Cells Dry 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

7. Types of Cells Dry Wet

8. 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

9. For Homework: • Read pg 511-513 • Answer questions p. 513 #4, 5, 7