1. Battery

2. Water Pump  A water current in a pipe is maintained by pressure.  The pressure provides potential energy to move the water.  A battery is a pump for electrons. v A PP d

3. Chemical Energy  Different metals hold their electrons with different energies. Energy into potentialEnergy into potential Electron as test chargeElectron as test charge  If two different metals can interact then they create an electric potential  V. Electromotive seriesElectromotive series  The electrode potential (V) for several metals: Lithium -3.0 Aluminum -1.7 Zinc -0.76 Iron -0.44 Lead -0.13 Hydrogen 0.00 Copper +0.34 Silver +0.80 Gold +1.3

4. Wet Cell  The ionic medium connecting the two metals is called an electrolyte. Must allow ions to moveMust allow ions to move  The chemical potential difference between copper and zinc in the cell at right is 1.1 V.

5. Dry Cell  Chemical cells are called batteries.  The lead acid car battery is a wet cell.  Batteries that use a damp paste are called dry cells. Alkaline batteryAlkaline battery

6. EMF  The potential difference from a chemical cell battery has the historical name electromotive force. EMF for shortEMF for short Symbol ESymbol E  The EMF is not a force. Electric potential is not force.Electric potential is not force.  The symbol for a battery is alternating long and short lines. Long side is more positive potentialLong side is more positive potential  

7. Ground  Electric potential has an arbitrary zero. Potential difference matters to charges.Potential difference matters to charges.  The earth’s surface is a useful reference point for potential, and is called ground.  The symbols for ground are downward triangles. Can be with linesCan be with lines Assumed to be 0 VAssumed to be 0 V

8. Complete Circuit  A conductive path is needed for current to flow. Connect positive to negativeConnect positive to negative  A complete path from positive to negative forms a circuit.  A load is needed to prevent current from flowing too much. Stones in the pipe for water flowStones in the pipe for water flow V load I

9. Electric Shock  The load can be an electric circuit or another conductor.  Skin and flesh conduct poorly. Better than a true insulator  The current may find a path to complete the circuit. next