Tree branch smolders; then explodes; from electricity?

[ScienceNostalgia101]

 

Wasn't sure whether this belonged in physics or chemistry, but being that from my familiarity with physics, heat makes objects LESS conductive, I assume it's chemistry that explains this. (And/or gives us enough to go on as to whether or not it's a hoax.)

 

Starting at 4 minutes and 13 seconds in, you can see a tree branch that fell on two power lines conduct smolder; presumably from conducting electricity between them. However, it takes more than a minute for any flames to become visible. Within seconds of the flame becoming visible, you can hear audible electrical arc sounds for a few seconds before the tree branch outright explodes, turning the smoke given off from grey to brown.

 

So what's going on here? Does the electricity directly cause chemical reactions that produce compounds more electrically conductive than those of the tree branch itself? Or does the smoldering cause that? As well, why the abrupt shift from flame to explosion if it took more than a minute for flames to appear?

[John Cuthber]

6 minutes ago, ScienceNostalgia101 said:

Wasn't sure whether this belonged in physics or chemistry, but being that from my familiarity with physics, heat makes objects LESS conductive, I

Only with metals.

With electrolytes and semiconductors, they generally conduct better when hot.

 

However, you may be right in thinking that chemistry gets involved, heating cellulose- a poor conductor- converts it to charcoal- a much better conductor.

 

Also, flames are quite good conductors compared to air

Edited January 15, 2020 by John Cuthber

[druS]

Not sure on thison your specific query, but to ignite the fuel has to be gasified. It is the gas that then ignites. There is a definite step process happening for fire.