Sock Physics - Experiments with Static Electricity

Zap!  Pull your clothes from the dryer and unless you've used one of those funny smelling anti-static papers you just might get a shock of electricity.   When the clothes tumble in the dryer and the water is removed, electrons are removed from their bonding atoms and static charges build on the clothing the same way walking across a rug on a dry day builds charge which is then released with a zap when you touch a conducting surface, like a door knob.  Zap!

When I tossed my clothes into a pile for sorting, I  watched as a loose strand from one sock reached upward as to defy gravity but stayed tethered to the sock.   Even knowing why this is so (or at least one explanation) it fascinates.  Over the next few minutes I held off sorting the clothes and took a few photographs.

Fig 1: Back lit sock with strand balanced against gravity by the repulsive force of static electricity

Even more amazing (to me), was the fine structure in the hair-like appendages that stood in repulsion to the main strand due to the repulsive forces of like charges.  When electrons are removed from neutrally charged atoms, a net positive charge remains.  The force between like charges is a repulsive one so the individual strands are forced apart.

Fig 2: fine structure detail from Fig 1 showing small fibers of the sock in mutual repulsion.

A few minutes later, the long strand was clearly losing the battle against gravity as the collected charges slowly dissipated as nitrogen and oxygen molecules took them away.   

Fig 3: Strand 5 minutes later

Eventually, the rebellious strand lost its charge and rejoined the sock.  

Fig 4:  Composite showing positions of strand over 5 minutes as it loses charge and settles under the force of gravity

Fig 5: Mouse-click for animation