[Shop-talk] sparky extension cord

[Wayne]

On 2/4/2010 10:22 PM, Eric J Russell wrote:
> block heater. I have noticed that when I unplug the extension cord from the
> block heater in the morning there is a noticeable spark as the connection is
> broken. Is this 'normal'? I haven't noticed sparks when unplugging other items

I'm going way out on the limb with a guess here... since it's been ~ 25 
years since I flunked out of EE.  But from what I remember, the spark is 
related to the collapse of the electric field, and its field energy 
being dissipated.  An inductive load of even just a coiled up heating 
element would have a bigger field than say, a light bulb, and make a 
bigger spark when disconnected.  Plus there's probably just enough extra 
shade under the hood to make it seem brighter.

-Wayne