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

  • #1

Main Question or Discussion Point

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
 

Answers and Replies

  • #2
174
0
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.
 
  • #3
2,193
2
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!!
 
  • #4
2,193
2
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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