Why does a lead acid battery spark when connecting to opposite terminals

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Discussion Overview

The discussion revolves around the behavior of lead acid batteries, specifically addressing the phenomenon of sparking when connecting opposite terminals and the flow of electrons in relation to a vehicle chassis. The scope includes conceptual understanding and technical explanations related to electrical circuits and battery operation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions why a lead acid battery sparks when the negative terminal is connected to the positive, suggesting that the electron imbalance on the cathode seeks to balance with the anode.
  • Another participant explains that sparking occurs just before the connection is made, likening it to a momentary capacitor effect where electrons attempt to flow from the anode to the cathode, resulting in an arc.
  • A participant affirms that electrons do flow through the circuit to power the load and return via the metal chassis, noting that the chassis is a convenient conductor rather than an ideal one.

Areas of Agreement / Disagreement

Participants express differing levels of understanding and curiosity about the phenomena, but there is no consensus on the explanations provided, and some questions remain unresolved.

Contextual Notes

There are assumptions about the behavior of electrons and the nature of the chassis as a conductor that are not fully explored or defined, leaving some aspects of the discussion open to interpretation.

Who May Find This Useful

Individuals interested in the workings of lead acid batteries, electrical circuits, and those seeking clarification on basic physics concepts related to electricity.

Edible Planet
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Sorry about the intrusion as I really don't belong here as I have absolutely no background in physics but I have a couple of questions regarding lead acid batteries that I have been unable to find answers to on the internet.

First question - why does a battery spark/arc when the negative is hooked directly up to the positive. I had thought that the electron imbalance on the cathode was seeking to balance out by "getting" to the anode and it seems that hooking up the cathode directly to the anode would most easily satisfy this imbalance.

Second question - When the anode is grounded to a vehicle chassis how do the electrons get from the cathode to the anode to balance the battery. Do they flow through the circuit, power the load and then return through the metal of the chassis? And if so how does the metal of the chassis not become polarized by the charge of the electrons as they move through it? Or are the electrons just moving through a field around the chassis to return to the anode. Very confusing! Can anyone give me a good explanation.

Thanks,

Scott
 
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For your first question, the sparking only occurs just before the wire from one end is connected to the other. You are effectively creating a capacitor for a moment. During this, electrons from the anode tries to flow to the cathode and arcs through the air, so you'll have a very tiny lightning bolt.
 
Edible Planet said:
Sorry about the intrusion as I really don't belong here as I have absolutely no background in physics but I have a couple of questions...

Intrusion? Not at all!
This site is open to everyone on the planet regardless of educational background.
As long as one posts specific questions and follows forum guidlines all is good and beneficial to us all.

Please feel most welcome here at PF!
 
Edible Planet said:
Do they flow through the circuit, power the load and then return through the metal of the chassis? ?

Yes. The sheet metal car chassis is just "convenient", not meant to be "ideal" for current flow. One "could" put more efficient copper wires connecting everything, but there is no need for that in most cases, hence the sheet metal of the car chassis is used.
 

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