E Static
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Static electricity – Wikipedia
Contact with the slide has left this child’s hair positively charged so that the individual hairs repel one another. The hair can also be attracted to the negatively charged slide surface.
Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors and transmits energy. [1]
A static electric charge can be created whenever two surfaces contact and have worn and separated, and at least one of the surfaces has a high resistance to electric current (and is therefore an electrical insulator). The effects of static electricity are familiar to most people because people can feel, hear, and even see the spark as the excess charge is neutralized when brought close to a large electrical conductor (for example, a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static shock – more specifically, an electrostatic discharge – is caused by the neutralization of a charge.
Causes[edit]
Materials are made of atoms that are normally electrically neutral because they contain equal numbers of positive charges (protons in their nuclei) and negative charges (electrons in “shells” surrounding the nucleus). The phenomenon of static electricity requires a separation of positive and negative charges. When two materials are in contact, electrons may move from one material to the other, which leaves an excess of positive charge on one material, and an equal negative charge on the other. When the materials are separated they retain this charge imbalance.
Contact-induced charge separation
Electrons can be exchanged between materials on contact; materials with weakly bound electrons tend to lose them while materials with sparsely filled outer shells tend to gain them. This is known as the triboelectric effect and results in one material becoming positively charged and the other negatively charged. The polarity and strength of the charge on a material once they are separated depends on their relative positions in the triboelectric series. The triboelectric effect is the main cause of static electricity as observed in everyday life, and in common high-school science demonstrations involving rubbing different materials together (e. g., fur against an acrylic rod). Contact-induced charge separation causes your hair to stand up and causes “static cling” (for example, a balloon rubbed against the hair becomes negatively charged; when near a wall, the charged balloon is attracted to positively charged particles in the wall, and can “cling” to it, appearing to be suspended against gravity).
Pressure-induced charge separation
Applied mechanical stress generates a separation of charge in certain types of crystals and ceramics molecules.
Heat-induced charge separation
Heating generates a separation of charge in the atoms or molecules of certain materials. All pyroelectric materials are also piezoelectric. The atomic or molecular properties of heat and pressure response are closely related.
Charge-induced charge separation
A charged object brought close to an electrically neutral object causes a separation of charge within the neutral object. Charges of the same polarity are repelled and charges of the opposite polarity are attracted. As the force due to the interaction of electric charges falls off rapidly with increasing distance, the effect of the closer (opposite polarity) charges is greater and the two objects feel a force of attraction. The effect is most pronounced when the neutral object is an electrical conductor as the charges are more free to move around. Careful grounding of part of an object with a charge-induced charge separation can permanently add or remove electrons, leaving the object with a global, permanent charge. This process is integral to the workings of the Van de Graaff generator, a device commonly used to demonstrate the effects of static electricity.
Removal and prevention[edit]
Removing or preventing a buildup of static charge can be as simple as opening a window or using a humidifier to increase the moisture content of the air, making the atmosphere more conductive. Air ionizers can perform the same task. [2]
Items that are particularly sensitive to static discharge may be treated with the application of an antistatic agent, which adds a conducting surface layer that ensures any excess charge is evenly distributed. Fabric softeners and dryer sheets used in washing machines and clothes dryers are an example of an antistatic agent used to prevent and remove static cling. [3]
Many semiconductor devices used in electronics are particularly sensitive to static discharge. Conductive antistatic bags are commonly used to protect such components. People who work on circuits that contain these devices often ground themselves with a conductive antistatic strap. [4][5]
In the industrial settings such as paint or flour plants as well as in hospitals, antistatic safety boots are sometimes used to prevent a buildup of static charge due to contact with the floor. These shoes have soles with good conductivity. Anti-static shoes should not be confused with insulating shoes, which provide exactly the opposite benefit – some protection against serious electric shocks from the mains voltage. [6]
Static discharge[edit]
The spark associated with static electricity is caused by electrostatic discharge, or simply static discharge, as excess charge is neutralized by a flow of charges from or to the surroundings.
The feeling of an electric shock is caused by the stimulation of nerves as the neutralizing current flows through the human body. The energy stored as static electricity on an object varies depending on the size of the object and its capacitance, the voltage to which it is charged, and the dielectric constant of the surrounding medium. For modelling the effect of static discharge on sensitive electronic devices, a human being is represented as a capacitor of 100 picofarads, charged to a voltage of 4000 to 35000 volts. When touching an object this energy is discharged in less than a microsecond. [7] While the total energy is small, on the order of millijoules, it can still damage sensitive electronic devices. Larger objects will store more energy, which may be directly hazardous to human contact or which may give a spark that can ignite flammable gas or dust.
Lightning[edit]
Lightning is a dramatic natural example of static discharge. While the details are unclear and remain a subject of debate, the initial charge separation is thought to be associated with contact between ice particles within storm clouds. In general, significant charge accumulations can only persist in regions of low electrical conductivity (very few charges free to move in the surroundings), hence the flow of neutralizing charges often results from neutral atoms and molecules in the air being torn apart to form separate positive and negative charges, which travel in opposite directions as an electric current, neutralizing the original accumulation of charge. The static charge in air typically breaks down in this way at around 10, 000 volts per centimeter (10 kV/cm) depending on humidity. [8] The discharge superheats the surrounding air causing the bright flash, and produces a shock wave causing the clicking sound. The lightning bolt is simply a scaled-up version of the sparks seen in more domestic occurrences of static discharge. The flash occurs because the air in the discharge channel is heated to such a high temperature that it emits light by incandescence. The clap of thunder is the result of the shock wave created as the superheated air expands explosively.
Electronic components[edit]
Many semiconductor devices used in electronics are very sensitive to the presence of static electricity and can be damaged by a static discharge.
The use of an antistatic strap is mandatory for researchers manipulating nanodevices.
Further precautions can be taken by taking off shoes with thick rubber soles and permanently staying with a metallic ground.
Static build-up in flowing flammable and ignitable materials[edit]
Static electricity is a major hazard when refueling an aircraft.
Discharge of static electricity can create severe hazards in those industries dealing with flammable substances, where a small electrical spark might ignite explosive mixtures. [9]
The flowing movement of finely powdered substances or low conductivity fluids in pipes or through mechanical agitation can build up static electricity. [10]
The flow of granules of material like sand down a plastic chute can transfer charge, which can be easily measured using a multimeter connected to metal foil lining the chute at intervals, and can be roughly proportional to particulate flow. [11] Dust clouds of finely powdered substances can become combustible or explosive. When there is a static discharge in a dust or vapor cloud, explosions have occurred. Among the major industrial incidents that have occurred are: a grain silo in southwest France, a paint plant in Thailand, a factory making fiberglass moldings in Canada, a storage tank explosion in
Glenpool, Oklahoma in 2003, and a portable tank filling operation and a tank farm in Des Moines, Iowa and Valley Center, Kansas in 2007. [12][13][14]
The ability of a fluid to retain an electrostatic charge depends on its electrical conductivity. When low conductivity fluids flow through pipelines or are mechanically agitated, contact-induced charge separation called flow electrification occurs. [15][16]
Fluids that have low electrical conductivity (below 50 picosiemens per meter), are called accumulators. Fluids having conductivity above 50 pS/m are called non-accumulators. In non-accumulators, charges recombine as fast as they are separated and hence electrostatic charge accumulation is not significant. In the petrochemical industry, 50 pS/m is the recommended minimum value of electrical conductivity for adequate removal of charge from a fluid.
Kerosines may have conductivity ranging from less than 1 picosiemens per meter to 20 pS/m. For comparison, deionized water has a conductivity of about
10, 000, 000 pS/m or 10 µS/m. [17]
Transformer oil is part of the electrical insulation system of large power transformers and other electrical apparatus. Re-filling of large apparatus requires precautions against electrostatic charging of the fluid, which may damage sensitive transformer insulation.
An important concept for insulating fluids is the static relaxation time. This is similar to the time constant τ (tau) within an RC circuit. For insulating materials, it is the ratio of the static dielectric constant divided by the electrical conductivity of the material. For hydrocarbon fluids, this is sometimes approximated by dividing the number 18 by the electrical conductivity of the fluid. Thus a fluid that has an electrical conductivity of 1 pS/m has an estimated relaxation time of about 18 seconds. The excess charge in a fluid dissipates almost completely after four to five times the relaxation time, or 90 seconds for the fluid in the above example.
Charge generation increases at higher fluid velocities and larger pipe diameters, becoming quite significant in pipes 8 inches (200 mm) or larger. Static charge generation in these systems is best controlled by limiting fluid velocity. The British standard BS PD CLC/TR 50404:2003 (formerly BS-5958-Part 2) Code of Practice for Control of Undesirable Static Electricity prescribes pipe flow velocity limits. Because water content has a large impact on the fluids dielectric constant, the recommended velocity for hydrocarbon fluids containing water should be limited to 1 meter per second.
Bonding and earthing are the usual ways charge buildup can be prevented. For fluids with electrical conductivity below 10 pS/m, bonding and earthing are not adequate for charge dissipation, and anti-static additives may be required. [citation needed]
Fueling operations[edit]
The flowing movement of flammable liquids like gasoline inside a pipe can build up static electricity. Non-polar liquids such as gasoline, toluene, xylene, diesel, kerosene and light crude oils exhibit significant ability for charge accumulation and charge retention during high velocity flow. Electrostatic discharges can ignite the fuel vapor. [18]
When the electrostatic discharge energy is high enough, it can ignite a fuel vapor and air mixture. Different fuels have different flammable limits and require different levels of electrostatic discharge energy to ignite.
Electrostatic discharge while fueling with gasoline is a present danger at gas stations. [19] Fires have also been started at airports while refueling aircraft with kerosene. New grounding technologies, the use of conducting materials, and the addition of anti-static additives help to prevent or safely dissipate the buildup of static electricity.
The flowing movement of gases in pipes alone creates little, if any, static electricity. [20] It is envisaged that a charge generation mechanism only occurs when solid particles or liquid droplets are carried in the gas stream.
In space exploration[edit]
Due to the extremely low humidity in extraterrestrial environments, very large static charges can accumulate, causing a major hazard for the complex electronics used in space exploration vehicles. Static electricity is thought to be a particular hazard for astronauts on planned missions to the Moon and Mars. Walking over the extremely dry terrain could cause them to accumulate a significant amount of charge; reaching out to open the airlock on their return could cause a large static discharge, potentially damaging sensitive electronics. [21]
Ozone cracking[edit]
A static discharge in the presence of air or oxygen can create ozone. Ozone can degrade rubber parts. Many elastomers are sensitive to ozone cracking. Exposure to ozone creates deep penetrative cracks in critical components like gaskets and O-rings. Fuel lines are also susceptible to the problem unless preventive action is taken. Preventive measures include adding anti-ozonants to the rubber mix, or using an ozone-resistant elastomer. Fires from cracked fuel lines have been a problem on vehicles, especially in the engine compartments where ozone can be produced by electrical equipment.
Energies involved[edit]
The energy released in a static electricity discharge may vary over a wide range. The energy in joules can be calculated from the capacitance (C) of the object and the static potential V in volts (V) by the formula E = ½CV2. [22] One experimenter estimates the capacitance of the human body as high as 400 picofarads, and a charge of 50, 000 volts, discharged e. g. during touching a charged car, creating a spark with energy of 500 millijoules. [23] Another estimate is 100–300 pF and 20, 000 volts, producing a maximum energy of 60 mJ. [24] IEC 479-2:1987 states that a discharge with energy greater than 5000 mJ is a direct serious risk to human health. IEC 60065 states that consumer products cannot discharge more than 350 mJ into a person.
The maximal potential is limited to about 35–40 kV, due to corona discharge dissipating the charge at higher potentials. Potentials below 3000 volts are not typically detectable by humans. Maximal potential commonly achieved on human body range between 1 and 10 kV, though in optimal conditions as high as 20–25 kV can be reached. Low relative humidity increases the charge buildup; walking 20 feet (6 m) on vinyl floor at 15% relative humidity causes buildup of voltage up to 12 kV, while at 80% humidity the voltage is only 1. 5 kV. [25]
As little as 0. 2 millijoules may present an ignition hazard; such low spark energy is often below the threshold of human visual and auditory perception.
Typical ignition energies are:
0. 017 mJ for hydrogen,
0. 2–2 mJ for hydrocarbon vapors,
1–50 mJ for fine flammable dust,
40–1000 mJ for coarse flammable dust.
The energy needed to damage most electronic devices[specify] is between 2 and 1000 nanojoules. [26]
A relatively small energy, often as little as 0. 2–2 millijoules, is needed to ignite a flammable mixture of a fuel and air. For the common industrial hydrocarbon gases and solvents, the minimum ignition energy required for ignition of vapor–air mixture is lowest for the vapor concentration roughly in the middle between the lower explosive limit and the upper explosive limit, and rapidly increases as the concentration deviates from this optimum to either side. Aerosols of flammable liquids may be ignited well below their flash point. Generally, liquid aerosols with particle sizes below 10 micrometers behave like vapors, particle sizes above 40 micrometers behave more like flammable dusts. Typical minimal flammable concentrations of aerosols lay between 15 and 50 g/m3. Similarly, presence of foam on the surface of a flammable liquid significantly increases ignitability. Aerosol of flammable dust can be ignited as well, resulting in a dust explosion; the lower explosive limit usually lies between 50 and 1000 g/m3; finer dusts tend to be more explosive and requiring less spark energy to set off. Simultaneous presence of flammable vapors and flammable dust can significantly decrease the ignition energy; a mere 1 vol. % of propane in air can reduce the required ignition energy of dust by 100 times. Higher than normal oxygen content in atmosphere also significantly lowers the ignition energy. [27]
There are five types of electrical discharges:
Spark, responsible for the majority of industrial fires and explosions where static electricity is involved. Sparks occur between objects at different electric potentials. Good grounding of all parts of the equipment and precautions against charge buildups on equipment and personnel are used as prevention measures.
Brush discharge occurs from a nonconductive charged surface or highly charged nonconductive liquids. The energy is limited to roughly 4 millijoules. To be hazardous, the voltage involved must be above about 20 kilovolts, the surface polarity must be negative, a flammable atmosphere must be present at the point of discharge, and the discharge energy must be sufficient for ignition. Further, because surfaces have a maximal charge density, an area of at least 100 cm2 has to be involved. This is not considered to be a hazard for dust clouds.
Propagating brush discharge is high in energy and dangerous. Occurs when an insulating surface of up to 8 mm thick (e. a teflon or glass lining of a grounded metal pipe or a reactor) is subjected to a large charge buildup between the opposite surfaces, acting as a large-area capacitor.
Cone discharge, also called bulking brush discharge, occurs over surfaces of charged powders with resistance above 1010 ohms, or also deep through the powder mass. Cone discharges aren’t usually observed in dust volumes below 1 m3. The energy involved depends on the grain size of the powder and the charge magnitude, and can reach up to 20 mJ. Larger dust volumes produce higher energies.
Corona discharge, considered non-hazardous.
See also[edit]
Electrical charge
Electrostatic discharge
Electrostatic generator
Electrostatics
Triboelectrification
Van de Graaff generator
Wimshurst machine
References[edit]
^ Dhogal (1986). Basic Electrical Engineering, Volume 1. Tata McGraw-Hill. p. 41. ISBN 978-0-07-451586-0.
^ “Ionizers and Static Eliminators”. GlobalSpec. 2009. Archived from the original on 2009-02-10. Retrieved 2009-04-13.
^ “Fabric Softener and Static”. Ask a Scientist, General Science Archive. US Department of Energy. 2003. Retrieved 2009-04-13.
^ Antistatic Bags for Parts. PC Chop Shop. John Wiley and Sons. 2004. ISBN 978-0-7821-4360-7. Retrieved 2009-04-13.
^ Antistatic Wrist Strap. Retrieved 2009-04-13.
^ “Safetoes: Safety Footwear”. Safetoes. Trojan Tooling. Retrieved 2009-04-13.
^ Carlos Hernando Díaz, Sung-Mo Kang, Charvaka Duvvury, Modeling of electrical overstress in integrated circuits Springer, 1995 ISBN 0-7923-9505-0 page 5
^ J. J. Lowke (1992). “Theory of electrical breakdown in air”. Journal of Physics D: Applied Physics. 25 (2): 202–210. Bibcode:1992JPhD… 25.. 202L. doi:10. 1088/0022-3727/25/2/012.
^ Kassebaum, J. H. & Kocken, R. A. (1995). “Controlling Static Electricity in Hazardous (Classified) Locations”. Petroleum and Chemical Industry 42nd Annual Conference Papers: 105–113. 1109/PCICON. 1995. 523945. ISBN 0-7803-2909-0. S2CID 110221915.
^ Wagner, John P. ; Clavijo, Fernando Rangel Electrostatic charge generation during impeller mixing of used transformer oil Department of Nuclear Engineering, Safety Engineering and Industrial Hygiene Program, Texas A&M University, College Station, online 21 August 2000; accessed Jan 2009 doi:10. 1016/S0304-3886(00)00019-X
^ Downie, Neil A., Exploding Disk Cannons, Slimemobiles and 32 Other Projects for Saturday Science (Johns Hopkins University Press (2006), ISBN 978-0-8018-8506-8, chapter 33, pages 259-266 “Electric Sand”
^ Hearn, Graham (1998). “Static electricity: concern in the pharmaceutical industry? “. Pharmaceutical Science & Technology Today. 1 (7): 286–287. 1016/S1461-5347(98)00078-9.
^ Storage Tank Explosion and Fire in Glenpool, Oklahoma April 7, 2003 National Transportation Safety Board
^ Static Spark Ignites Flammable Liquid during Portable Tank Filling Operation Archived 2009-01-17 at the Wayback Machine Chemical Safety Board October 29, 2007
^ Egorov, V. N. (1970). “Electrification of petroleum fuels” (PDF). Khimiya I Tekhnologiya Topliv I Masel. 4: 20–25. [dead link]
^ Touchard, Gérard (2001). “Flow electrification of liquids”. Journal of Electrostatics. 51–52: 440–447. 1016/S0304-3886(01)00081-X.
^ Chevron Corporation Aviation Fuels Technical Review Archived 2009-03-19 at the Wayback Machine 2006, accessed Dec 2008
^ Hearn, Graham Static electricity – guidance for Plant Engineers – Wolfson Electrostatics University of Southampton 2002; accessed Dec 2008
^ “CarCare – Auto Clinic” Popular Mechanics, April 2003, p. 163.
^ Kinzing, G. E., ‘Electrostatic Effects in Pneumatic Transport: Assessment, Magnitudes and Future Direction’, Journal Pipelines, 4, 95–102, 1984
^ “NASA – Crackling Planets”. Retrieved 2021-02-23.
^ Nomograms for capacitive electrostatic discharge risk assessment. Retrieved on 2010-02-08.
^ “High voltage safety: VandeGraaff Electrostatic Generator”. Retrieved 2010-01-27.
^ Index. Retrieved on 2011-03-17.
^ M. A. Kelly, G. E. Servais, T. V. Pfaffenbach An Investigation of Human Body Electrostatic Discharge, ISTFA ’93: The 19th International Symposium for Testing & Failure Analysis, Los Angeles, California, USA/15–19 November 1993.
^ “ESD Terms”. Archived from the original on 2004-09-17. Retrieved 2010-01-27.
^ Static Electricity Guidance for Plant Engineers. Graham Hearn – Wolfson Electrostatics, University of Southampton.
External links[edit]
Static Electricity 3: More About Static Electricity – Science NetLinks
Purpose
To reinforce the concept that static electricity is a phenomenon that involves positive and negative charges.
Context
This lesson is the third of a four-part series on static electricity. These lessons are meant to help students understand that static electricity is a phenomenon that involves positive and negative charges. An understanding of static electricity must begin with the concept that all matter is composed of atoms, and all atoms are composed of subatomic particles among which are the charged particles known as electrons and protons. Protons carry a positive charge (+), and electrons carry a negative charge (-). The number of electrons in an atom—ranging from one up to about 100—matches the number of charged particles, or protons, in the nucleus, and determines how the atom will link to other atoms to form molecules. Electrically neutral particles (neutrons) in the nucleus add to its mass but do not affect the number of electrons and so have almost no effect on the atom’s links to other atoms (its chemical behavior). To further understanding about static electricity, you should help your students to make connections between their day-to-day experiences with static electricity—such as lightning, receiving shocks after shuffling across a carpet, taking clothes that cling to each other out of the dryer, combing their hair in the wintertime—with the static activities conducted in the classroom. Ask them to try to describe and explain their everyday experiences with static in the terms they are learning: repel, attract, static charge, electron transfer. It is important that students grasp the concept that oppositely charged objects attract each other and like charged objects repel each other. It is less important that they are able to recall which materials tend to acquire negative or positive charges. When two different materials come into close contact, for example, felt rubbing against a balloon or two air masses in a storm cloud, electrons may be transferred from one material to the other. When this happens, one material ends up with an excess of electrons and becomes negatively charged, while the other ends up with a deficiency of electrons and becomes positively charged. This accumulation of imbalanced charges on objects results in the phenomena we commonly refer to as static electricity. When students first begin to understand atoms, they cannot confidently make the distinction between atoms and molecules. Students often get the idea that atoms somehow just fill matter up rather than the correct idea that the atoms are the matter. Middle-school students also have trouble with the idea that atoms are in continual motion. Coming to terms with these concepts is necessary for students to make sense of atomic theory and its explanatory power. (Benchmarks for Science Literacy, p. 75. ) In Static Electricity 1: Introducing Atoms, students are asked to review websites to learn about the atom’s basic structure and the positive and negative charges of its subparticles. This lesson lays the groundwork for further study of static and current electricity by focusing on the idea of positive and negative charges at the atomic level. Due to the amount and complexity of the information related to this topic, students will gain an understanding of these concepts over time. It is important that they explore this topic in a variety of contexts. Static Electricity 2: Introducing Static Electricity helps expand students’ concepts about atoms and how they relate to static electricity. In this lesson, students perform some simple experiments, creating static electricity to demonstrate how opposite charges attract each other and like charges repel each other. Then, students explore a website that further explains these concepts. Static Electricity 3: More About Static Electricity helps expand students’ concepts about atoms and how they relate to static electricity. In this lesson, students explore a website to investigate concepts related to static electricity. Then, students perform experiments in which they create static electricity and demonstrate how opposite charges attract each other and like charges repel each other. Static Electricity 4: Static Electricity and Lightning introduces students to concepts about lightning and how they relate to static electricity. In this lesson, students explore a variety of websites to learn about lightning and then explain in their own words what causes lightning and how it is related to static electricity.
Motivation
Before exploring the website, review with students some of the concepts leading up to this lesson.
Ask students these questions:
What are atoms? (Atoms are some of the tiniest particles of any material or element. Atoms are the building blocks of matter. )
What are the subatomic particles that make up an atom? (They are protons, electrons, and neutrons. )
What kind of electrical charge do protons, electrons, and neutrons have? (Protons have a positive charge, electrons have a negative charge, and neutrons do not have any charge. )
What often happens when you rub one object with another object? (When you rub one object with another, one of the objects will pick up some of the other object’s electrons. )
Explain what causes clothes to stick together when they come out of the dryer or a shock to occur after shuffling across the carpet and then touching a door handle. (The rubbing of clothes in a dryer or shoes on the carpet causes an imbalance of electrons. These electrons are then attracted to objects with the opposite charge. )
Development
In this lesson, students will explore the Static Electricity section of the Science Made Simple website to learn more about the causes and effects of static electricity. Then, they will perform experiments demonstrating that opposite charges attract and like charges repel.
It may be useful to have students work together in pairs so they can help each other understand the facts and concepts in the online activity.
Distribute the More About Static Electricity student sheet. Ask students to answer the questions from the student sheet, as they explore the Static Electricity resource.
After students have had an opportunity to complete Part 1, lead a discussion of the questions they answered on the student sheets:
What are three examples of static electricity? (Some examples might include: walking across a carpet and touching a metal door handle and pulling your hat off and having your hair stand on end. )
When is there a positive charge? (A positive charge occurs when there is a shortage of electrons. )
When is there a negative charge? (A negative charge occurs when there are too many electrons. )
What role does friction play in static electricity? (Friction, or rubbing together of two objects, causes an imbalance of electrons by transferring electrons from one object to another. )
When do objects attract each other? (Opposite charges attract. If one object has a negative charge and the other a positive charge, then they will be attracted to each other. )
When do objects repel each other? (Like charges repel. If two objects both have a negative charge, then they will repel each other. )
Next, have students perform the activities as directed on Parts 2 and 3 of the student sheet. In Part 2, students will conduct the activity called Opposite Charges Attract. This is a simple demonstration of the effect of static electricity when objects with opposite charges attract each other using an inflated balloon, a few small pieces of paper, and wool.
After students have conducted the activity and recorded their answers to the questions, discuss with the class how the activity shows that opposite charges attract. Students should be able to explain that the paper is attracted to the balloon because the balloon has a negative charge and the paper has a positive charge. Thus, the opposite charges attract each other.
In Part 3, the Similar Charges Repel activity, students conduct another activity to demonstrate the effect of static electricity when objects with the same charge repel each other. Using two plastic combs, a piece of cotton string, and a piece of wool, students will charge two plastic combs and see what happens when the two combs come together.
After students have conducted the activity and recorded their answers, discuss with the class how the activity shows that similar charges repel. Students should be able to explain that both combs have an excess of electrons that was created by rubbing them on the wool. The suspended comb rotates away from the one in your hand because they both have the same charge.
Assessment
To assess students’ understanding, ask them to perform an experiment:
Supply each student with a plastic comb and several small pieces of paper. Ask students to find a way to use the comb to pick up the pieces of paper without touching them.
After students have completed their experiment, ask them to write down the steps they used to perform the experiment and whether the experiment worked. Also, ask students to write a brief explanation of what causes static electricity.
To perform the experiment, students should rub the comb against a wool object or another object that easily gives up its electrons. When the comb is rubbed, it becomes negatively charged with an excess of electrons. When the comb is placed close to the paper, the positive charges from the paper are attracted to the negative charges from the comb.
Students should be able to explain that static electricity is created when an object gives up or gains electrons.
Extensions
Continue exploring these concepts with the next Science NetLinks lesson in this series, Static Electricity 4: Static Electricity and Lightning.
The following Internet resources can be used to further explore the topics related to static electricity:
Activities to explore Static Electricity, on the Boston Museum of Science site, provides background information for the teacher and includes several experiments demonstrating static electricity.
Static Electricity, part of Frankenstein’s Lightning Laboratory on the Atoms Family site, is an experiment that uses a plastic comb, wool cloth, puffed rice, and a large plastic bag with tie.
Other activities in Frankenstein’s Lightning Laboratory include Electrical Safety and Fruity Electricity.
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Frequently Asked Questions about e static
What is static E?
Static electricity is an imbalance of electric charges within or on the surface of a material. … A static electric charge can be created whenever two surfaces contact and have worn and separated, and at least one of the surfaces has a high resistance to electric current (and is therefore an electrical insulator).
What are 3 examples of static?
What are three examples of static electricity? (Some examples might include: walking across a carpet and touching a metal door handle and pulling your hat off and having your hair stand on end.) When is there a positive charge? (A positive charge occurs when there is a shortage of electrons.)
Is static electricity positive?
The protons are positively charged, the electrons are negatively charged, and the neutrons are neutral. … Static electricity is the result of an imbalance between negative and positive charges in an object. These charges can build up on the surface of an object until they find a way to be released or discharged.Nov 19, 2019
