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Lead Acid (Car) Battery

Batteries don’t store charge. They store energy. A chemical battery works because electrons like to leave some materials to go to others. The change in energy when the electron goes “downhill” becomes available as electric POTENTIAL between the battery terminals. Lead Acid (Car) Battery.

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Lead Acid (Car) Battery

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  1. Batteries don’t store charge. They store energy.A chemical battery works because electrons like to leave some materials to go to others. The change in energy when the electron goes “downhill” becomes available as electric POTENTIAL between the battery terminals

  2. Lead Acid (Car) Battery The rxn on the right will not go in the direction indicated unless the electrolyte sol’n potential is closer than 1.685 V to the + electrode potential. i.e. the + electrode can be no more than 1.685 V higher in potential than the electrolyte sol’n. Pb+2 is in the form of solid lead sulfate on the electrodes. When “discharged”, both electrodes turn into lead sulfate.

  3. Lead Acid (Car) Battery The rxn on the left will not go in the direction indicated unless the electrolyte potential is closer than 0.356 V to the - electrode potential. i.e. the - electrode can be no more than 0.356 V lower in potential than the electrolyte soln.

  4. Lead Acid (Car) Battery Overall, then, the reactions will STOP when the potential between the +/- electrodes is 2.041V. Only a tiny tiny tiny amount of charge needs to build up on the electrodes for the reaction to stop. How much? But if you connect the electrodes with a resistive wire, the reaction will start to go as the potential drops a hair below 2.041V.

  5. Lead Acid (Car) Battery What happens if you force the potential difference to be higher than 2.041 V? The reactions run backwards! Lead sulfate turns into lead oxide and lead (metallic). This is charging the battery.

  6. Lead Acid (Car) Battery Note that the rxn doesn’t make a big “reservoir” of electrons. The battery doesn’t die because it runs out of stored electrons. It doesn’t store electrons. It “pumps” electrons “on demand”, i.e. when the potential falls below 2.041 V.

  7. The two electrodes of an ideal V volt battery are shown. The field lines for the electric field between the electrodes are shown when nothing is attached to the electrodes. The electrodes have a separation = d.A resistive wire of length L is then attached to the battery.What is the electric field in the wire, when steady state is reached? A] 0 B] it varies, but averages to V/d C] it varies, but averages to V/L D] it is V/L everywhere in the wire E] no way to determine

  8. The two electrodes of an ideal V volt battery are shown. The field lines for the electric field between the electrodes are shown when nothing is attached to the electrodes. The electrodes have a separation = d.A resistive wire of length L is then instantaneously attached to the battery.What is the electric field in the wire, immediately after attaching it? A] 0 B] it varies, but averages to V/d C] it varies, but averages to V/L D] it is V/L everywhere in the wire E] no way to determine

  9. Where on this wire will negative charges “build up” (a tiny amount) B A

  10. Assume wires have zero resistance

  11. Assume wires have zero resistance

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