Static Electricity - Physics Notes PDF

**PHYSICS 4-3, SEM 2 WK1**: Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Topic: **Electricity** Class: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Sub-topic: **Static Electricity** **[What is Static Electricity?] and Charge.** **Support Video Link: ** **Static electricity can be a nuisance or even a dang...

**PHYSICS 4-3, SEM 2 WK1**: Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Topic: **Electricity** Class: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Sub-topic: **Static Electricity** **[What is Static Electricity?] and Charge.** **Support Video Link: ** **Static electricity can be a nuisance or even a danger. The energy that makes your hair to stand on end can also damage electronics and cause explosions. However, properly controlled and manipulated, it can also be a tremendous boon to modern life.** **"Electric charge is a fundamental property of matter. Nearly all electric charge in the universe is carried by protons and electrons. Protons are said to have a charge of +1 electron unit, while electrons have a charge of −1, although these signs are completely arbitrary. Because protons are generally confined to atomic nuclei, which are in turn imbedded inside atoms, they are not nearly as free to move as are electrons. Therefore, when we talk about electric current, we nearly always mean the flow of electrons, and when we talk about static electricity, we generally mean an imbalance between negative and positive charges in objects.** **[Causes of Static Charge buildup.]** **One common cause of static charge buildup is contact between solid materials. According to the University of Hawaii, "When two objects are rubbed together to create static electricity, one object gives up electrons and becomes more positively charged while the other material collects electrons and becomes more negatively charged." This is because one material has weakly bound electrons, and the other has many vacancies in its outer electron shells, so electrons can move from the former to the latter creating a charge imbalance after the materials are separated. Materials that can lose or gain electrons in this way are called triboelectric, according to Northwestern University. One common example of this would be shuffling your feet across carpet, particularly in low humidity which makes the air less conductive and increases the effect.** **Because like charges repel each other, they tend to migrate to the extremities of the charged object in order to get away from each other. This is what causes your hair to stand on end when your body takes on a static charge, according to the Library of Congress. When you then touch a grounded piece of metal such as a screw on a light switch plate, this provides a path to ground for the charge that has built up in your body. This sudden discharge creates a visible and audible spark through the air between your finger and the screw. This is due to the high potential difference between your body and the ground which can be as much as 25,000 volts.** **[Dangers of static charge buildup.]** **In addition to causing in a painful shock, these sudden high-voltage discharges can provide a source of ignition for flammable substances. Static shock can also damage delicate electronics. According to NASA, a simple spark from a finger can damage sensitive components and render them unusable, so precautions must be taken such as keeping circuit boards in conductive plastic bags and wearing grounding straps to dissipate static charge continuously from your body.** **Another source of static charge is the motion of fluids through a pipe or hose. If that fluid is flammable --- such as gasoline --- a spark from a sudden discharge could result in a fire or explosion. People who handle liquid fuels should take great care to avoid charge buildup and sudden discharge. In an interview, Daniel Marsh, professor of physics at Missouri Southern State University, warned that when putting gasoline in your car, you should always touch a metal part of the car after getting out to dissipate any charge that might have developed by sliding across the seat. Also, when buying gas for your lawn mower, you should always take the can out of your car and place it on the ground while filling it. This dissipates the static charge continuously and keeps it from building up enough to create a spark.** **Large tank farms present an even greater danger of fire and explosions, so guidelines are in place so to minimizing static generation, preventing charge accumulation, avoiding spark discharge, and controlling the environment inside the tank.** **[Application of Static Electricity:]** **(i)** An electrostatic precipitator removes smoke and dust from waste gases going up the chimneys of factories and power stations. The diagram shows how the precipitator works. The wire grid is kept highly charged so that a continuous corona discharge occurs between the grid and the earthed metal plates. This discharge involves a continuous stream of ions which attach themselves to the dust particles in the gas going up the chimney. The charged dust particles are now repelled from the wire grid and attracted to the earthed plates where they become deposited. These plates are tapped from time to time so that the dust and smoke particles fall down the chimney and are removed at the bottom. **(ii) Revealing of finger prints on surfaces.**  **A concealed finger prints on the surface of a paper such as a bank note, or a plastic object such as a handbag, can be revealed using charged powder. A metal plate with a coating of a fine powder (e.g. silicon carbide) is given a high positive charge from a 10 000 Volts supply. The specimen is connected to a negative terminal of the supply. 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 finger print. Elsewhere on the specimen the particles lose their positive charge, pick up a negative charge and are repelled back to the plate below. The finger print in the photograph was made visible by this electrostatic process at the University of Manchester Institute of Science and Technology. The finger print, which is on paper, was invisible before the process was used. The same kind of idea is used in most photocopiers, where a dark powder or 'toner' is attracted to charge places on a metal plate and is then transferred onto paper.** **[Electric Fields: Video Support:] ** **An electric field is a space around a charged particle where the particle exerts electric force on other charged particles. Because of their force fields, charged particles can exert force on each other without actually touching. Electric fields are generally represented by arrows, as you can see in the Figure to the right. The arrows show the direction of electric force around a positive particle and a negative particle. Below are different Electric Fields mappings.** **[Lesson Assessment:]** ***Assignment: Answer the following in your notebooks.*** ***(i) Students are to State and Explain (pictures included) three other uses of Static Electricity.*** ***(ii) Answer the Question, What is lightning?***