Static Charge and the Van de Graaf Generator

Static Charge Latin word “Stasis” which means “Stays” Latin word “Stasis” which means “Stays” Objects are typically “Neutral” w/ the same # of protons and electrons Objects are typically “Neutral” w/ the same # of protons and electrons They can become “charged” by gaining or losing electrons – They can become “charged” by gaining or losing electrons – NOT PROTONS! – They stay in the nucleus! NOT PROTONS! – They stay in the nucleus! The buildup of these charges is “Static Electricity” The buildup of these charges is “Static Electricity” In Static Electricity the charges build up and STAY; In Static Electricity the charges build up and STAY; they don’t flow as they do in electric currents they don’t flow as they do in electric currents

Transferring Static Charge Friction – electrons are transferred from rubbing Friction – electrons are transferred from rubbing Some objects have a greater affinity for electrons Some objects have a greater affinity for electrons Example: you get shocked after walking on carpet in socks Example: you get shocked after walking on carpet in socks

Transferring Static Charge Conduction – electrons are transferred by direct contact w/ another object. Conduction – electrons are transferred by direct contact w/ another object. Hair stands on end w/ Van de Graff machine because all of the hair strands have the same charge and repel each other. They are trying to discharge the electrons. Hair stands on end w/ Van de Graff machine because all of the hair strands have the same charge and repel each other. They are trying to discharge the electrons.

Transferring Static Charge Induction – the force field of a highly negatively charged object pushes the electrons away from nearby objects causing them to become + charged, they then are attracted to each other. Induction – the force field of a highly negatively charged object pushes the electrons away from nearby objects causing them to become + charged, they then are attracted to each other. i.e. statically charged balloon attracts small pieces of torn up paper i.e. statically charged balloon attracts small pieces of torn up paper

Static Discharge Objects don’t hold a static charge forever – objects tend toward equilibrium – they “want” to be neutral Objects don’t hold a static charge forever – objects tend toward equilibrium – they “want” to be neutral When electrons move toward this equilibrium – static discharge occurs When electrons move toward this equilibrium – static discharge occurs Humidity – water (a polar molecule) vapor in the air pulls electrons off negatively charged objects, preventing static charges to build up Humidity – water (a polar molecule) vapor in the air pulls electrons off negatively charged objects, preventing static charges to build up Sparks & Lightning - objects reaching static equilibrium Sparks & Lightning - objects reaching static equilibrium

The Van de Graaf Generator The Van de Graaf uses a moving belt to create an electrostatic charge. The charge will accumulate in the hollow metal globe. If you are holding on to the globe as it builds this charge, you will become charged also. The Van de Graaf uses a moving belt to create an electrostatic charge. The charge will accumulate in the hollow metal globe. If you are holding on to the globe as it builds this charge, you will become charged also.