BatteryBattery

Water PumpWater Pump A water current in a pipe is A water current in a pipe is

maintained by pressure.maintained by pressure.

The pressure provides The pressure provides potential energy to move the potential energy to move the water.water.

A battery is a pump for A battery is a pump for electrons.electrons.

v

A

P

PAdE

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Chemical EnergyChemical Energy Different metals hold their Different metals hold their

electrons with different electrons with different energies.energies.• Energy into potentialEnergy into potential

• Electron as test chargeElectron as test charge

If two different metals can If two different metals can interact then they create an interact then they create an electric potential electric potential VV..• Electromotive seriesElectromotive series

The electrode potential (V) for The electrode potential (V) for several metals:several metals:• Lithium -3.0Lithium -3.0

• Aluminum -1.7Aluminum -1.7

• Zinc -0.76Zinc -0.76

• Iron -0.44Iron -0.44

• Lead -0.13Lead -0.13

• Hydrogen 0.00Hydrogen 0.00

• Copper +0.34Copper +0.34

• Silver +0.80Silver +0.80

• Gold +1.3Gold +1.3

Wet CellWet Cell The ionic medium connecting The ionic medium connecting

the two metals is called an the two metals is called an electrolyte.electrolyte.• Must allow ions to moveMust allow ions to move

The chemical potential The chemical potential difference between copper and difference between copper and zinc in the cell at right is 1.1 V.zinc in the cell at right is 1.1 V.

Dry CellDry Cell Chemical cells are called Chemical cells are called

batteries.batteries.

The lead acid car battery is The lead acid car battery is a wet cell.a wet cell.

Batteries that use a damp Batteries that use a damp paste are called dry cells.paste are called dry cells.• Alkaline batteryAlkaline battery

EMFEMF

The potential difference from a chemical cell battery has The potential difference from a chemical cell battery has the historical name the historical name electromotive forceelectromotive force..• EMF for shortEMF for short• Symbol Symbol EE

The EMF is not a force.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 The symbol for a battery is alternating long and short lines.lines.• Long side is more positive potentialLong side is more positive potential

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GroundGround

Electric potential has an arbitrary zero.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 The earth’s surface is a useful reference point for potential, and is called potential, and is called groundground..

The symbols for ground are downward triangles.The symbols for ground are downward triangles.• Can be with linesCan be with lines• Assumed to be 0 V Assumed to be 0 V

Complete Circuit Complete Circuit A conductive path is needed A conductive path is needed

for current to flow.for current to flow.• Connect positive to negativeConnect positive to negative

A complete path from positive A complete path from positive to negative forms a circuit.to negative forms a circuit.

A load is needed to prevent A load is needed to prevent current from flowing too much.current from flowing too much.• Stones in the pipe for water Stones in the pipe for water

flowflow

V load

I

Electric Shock Electric Shock The load can be an The load can be an

electric circuit or another electric circuit or another conductor.conductor.

Skin and flesh conduct Skin and flesh conduct poorly.poorly.• Better than a true Better than a true

insulatorinsulator

The current may find a The current may find a path to complete the path to complete the circuit.circuit.

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