Q: If you walk briskly across a carpet , you often experience a spark on touching a door knob (a)what causes this? (b)how mighet it be prevented.
a; friction between two objects capably of holding an electrical charge.
b. reduce the friction potential, by increase humility in the air, use a anti static spray, or change one of the elements to a item that can not hold a static charge, such as wearing rubber soled shoes instead of leather soles.
Electrostatics is the branch of science that deals with the phenomena arising from stationary or slow-moving electric charges.
Since classical antiquity it was known that some materials such as amber attract light particles after rubbing. The Greek word for amber, Î®Î»ÎµÎºÏÏÎ¿Î½ (electron), was the source of the word ‘electricity’. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb’s law. Even though electrostatically induced forces seem to be rather weak, the electrostatic force between e.g. an electron and a proton, that together make up a hydrogen atom, is about 40 orders of magnitude stronger than the gravitational force acting between them.
When you are walking across a carpet your feat come in contact with the carpet and upon breaking contact you “brush off” electrons onto your self resulting in you having a net negative charge when you touch the metal conductor your body discharges itself through your finger resulting in the shock you experience.
You could prevent it by stepping on moist soil before touching metal objects or have a metal object touching you when you accumulate the charge and then use that object to hold and touch it to the other metal object that would normally shock you, this way you’ll be discharged but you wont feel it.
Electrostatics is a set of physical principles used to understand the forces among charged particles and charged bodies, when any relative motion of charges is insignificant.
(a)what causes this?
I’ve never experienced it, but I know it is caused by exchange of electrons among you and the carpet such that one of you has an electron surplus and the other an electron deficit. The spark experienced between you and the doorknob is you attempting to neutralize yourself with the initially neutral doorknob which is conductive.
(b)how might it be prevented?
Walk more carefully such as to not make as much of a scuffing with the floor.
b) by frequently discharging yourself by touching large metal objects.