STATIC ELECTRICITY UM Physics Demo Lab 07/2013 ANALYSIS On a dry day, many hapless individuals feel the shock of static electricity after traversing a carpet and touching a door-knob. The circumstances that precede such an event are exactly what Ben Franklin first used to observe and differentiate electric charge. Charged Particles All elements are a balance of charged particles: positively charged protons and negatively charged electrons. When the particles are present in equal numbers, the system has no net charge. When there is more of one type of charge (either electrons or protons), then the net charge is either positive or negative. Figure 1: Net charges When there is a net charge of either positive or negative, the system strongly wants to return to equilibrium. That strong desire can produce a spark. This is the phenomenon that causes lightning bolts. Storm clouds separate charges until finally the electric fields are strong enough to force ions onto the earth in a bolt of lightning. Friction From chemistry we learn that elements have electronegativity. This means that some elements are willing to surrender electrons, and others want to capture electrons. This transfer of electrons between these two types of material can be aided by rubbing the materials together. We did this intentionally by rubbing the Teflon and the fur; many people do it unintentionally when they rub their shoes across a carpeted floor or their clothes across a car seat. Figure 2: Static charge build-up on person just before touching the conducting door-knob. Conduction Charge passes from one material to another when the two materials are in contact. This phenomenon is called conduction. When a person across a carpet with their excess charge toward a conducting door, the excess charge passes between the two in the form of a spark. Materials are classified in two ways: conductors pass charge readily, and insulators resist passing charge.
STATIC ELECTRICITY UM Physics Demo Lab 07/2013 ANALYSIS On a dry day, many hapless individuals feel the shock of static electricity after traversing a carpet and touching a door-knob. The circumstances that precede such an event are exactly what Ben Franklin first used to observe and differentiate electric charge. Charged Particles All elements are a balance of charged particles: positively charged protons and negatively charged electrons. When the particles are present in equal numbers, the system has no net charge. When there is more of one type of charge (either electrons or protons), then the net charge is either positive or negative. Figure 1: Net charges When there is a net charge of either positive or negative, the system strongly wants to return to equilibrium. That strong desire can produce a spark. This is the phenomenon that causes lightning bolts. Storm clouds separate charges until finally the electric fields are strong enough to force ions onto the earth in a bolt of lightning. Friction From chemistry we learn that elements have electronegativity. This means that some elements are willing to surrender electrons, and others want to capture electrons. This transfer of electrons between these two types of material can be aided by rubbing the materials together. We did this intentionally by rubbing the Teflon and the fur; many people do it unintentionally when they rub their shoes across a carpeted floor or their clothes across a car seat. Figure 2: Static charge build-up on person just before touching the conducting door-knob. Conduction Charge passes from one material to another when the two materials are in contact. This phenomenon is called conduction. When a person across a carpet with their excess charge toward a conducting door, the excess charge passes between the two in the form of a spark. Materials are classified in two ways: conductors pass charge readily, and insulators resist passing charge.