Static Electricity: Charge Imbalance and Buildup

• Static electricity is a nuisance but can damage electronics and cause explosion
• Static electricity occurs because of an imbalance between negative and positive charges in objects
• Electric charge is a fundamental property of protons and electrons
• Protons have a charge of +1 electron unit
• Electrons have a charge of -1
• Electrons are more easily moved than protons because protons are confined to the atomic nuclei

Causes of Static Charge Buildup

• Static charge buildup is due to contact between solids
• When objects are rubbed together, one object gives up electrons becoming more positively charged
• The other object collects electrons to become more negatively charged
• This is because one material has weakly bound electrons while the other has vacancies in its outer electron shells
• Materials that lose or gain electrons are called triboelectric
• An example includes shuffling feet across carpet, particularly in low humidity which makes the air less conductive
• Like charges repel each other and migrate to the extremities of a charged object
• Touching a grounded piece of metal provides a path to ground for built up charge
• This sudden discharge creates a visible and audible spark through the air of up to 25,000 volts

Dangers of Static Charge Buildup

• Static charge buildup can cause painful shocks
• It can provide a source of ignition for flammable substances
• Static shock can damage delicate electronics
• Sparks from a finger can damage sensitive components
• Preventative measures should be taken such as keeping circuit boards in conductive plastic bags and wearing grounding straps
• Motion of fluids through a pipe or hose is another source of static charge
• If fluid is flammable, a spark could cause a fire or explosion
• Liquid fuel handlers must avoid charge buildup and sudden discharge by touching a metal part of the car after getting out
• Gas cans should be placed on the ground while filling
• Guidelines are in place for large tank farms to minimize static generation

Application of Static Electricity

• Electrostatic precipitators removes smoke and dust from waste gases
• A wire grid is kept highly charged so that a continuous corona discharge occurs between the grid and earthed metal plates
• The discharge involves a continuous stream of ions which attach themselves to the dust particles
• Charged dust particles are repelled from the wire grid and attracted to the earthed plates where they become deposited

Revealing Fingerprints on Surfaces

• Concealed fingerprints on paper or plastic can be revealed using charged powder
• A metal plate with a coating of fine powder is given a high positive charge
• The specimen is connected to a negative terminal
• The powder becomes positively charged and is repelled from the metal plate towards the specimen
• When the powder strikes the specimen, particles stick only to the tacky ridges of the fingerprint
• The particles lose their positive charge, pick up a negative charge, and are repelled back to the plate below
• A dark powder or 'toner' is attracted to charge places on a metal plate and is then transferred onto paper

Electric Fields

• An electric field is a space around a charged particle where that particle exerts electric force on other charged particles
• Charged particles can exert force without touching
• Electric fields are represented by arrows showing the direction of electric force around a positive particle and a negative particle

Learn about static electricity, its causes, and the fundamental properties of electric charges. Understand how the imbalance between positive and negative charges leads to static charge buildup through contact between solids. Explore the concept of triboelectric materials and real-world examples like shuffling feet on carpet.