2007 - V 4/15 615-3085 (10-091) Electrostatic .

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2007 - v 4/15615-3085 (10-091)ElectrostaticDemonstration Kit Experiments ApplicationsSCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/15Warranty and Parts:We replace all defective or missingparts free of charge. Additional replacement parts may be ordered toll-free. Weaccept MasterCard, Visa, checks andSchool P.O.s. All products warranted tobe free from defect for 90 days. Doesnot apply to accident, misuse or normalwear and tear. Intended for children 13years of age and up. This item is not atoy. It may contain small parts that canbe choking hazards. Adult supervisionis required.Maintenance:For best results, maintain these kitmaterials between each use.1. Protect insulating materials fromsalt spray, chemical flames and perspi ration. They coat them with a film ofmoisture which conducts away elec triccharges, affecting your ex periments.You can remove any moisture filmbuildup with a rinse of distilled water.2. Your experiments are BEST performed in a dry room. Avoid handlingthe material with moist hands.3. At high humidities (over 80%),lint strands may cause short circuitsor act as discharge points. If using anelec trophorus, note that damp lint diminishes the potential of metal surfacesand makes them less effective. See Page11 for a list common materials and theireffectiveness as charge generators.4. Watch for radiation, open flamesetc. that might ionize the nearby air.These will slowly dis charge the bodiesyou have charged and are testing.Product Description:See drawings and photos on next page.body to other bodies. Hold by plastic(insulator) handle. Ball “carries” charge. Friction Rods (polystyrene, acrylic, glass, nylon, PVC and polyethylene)and Friction Surfaces (acetate cloth,polyethylene film) are basic materials forgenerating electrical charges by rubbingrod against surface. (Additional materiallike hard rubber comb, flannel/wool/silkcloth can be added. Conductive coated ball has ahook to suspend with a piece of threador fishline. Use it to detect charges andminal to be screwed on to the rod end.This pro vides a direct conductive channel to any electric charge landing on theterminal, all the way to the foil leaves.[Note: When the leaves are charged, theyspread apart because of similar chargeson both leaves. Otherwise, in their neutralstate, they remain collapsed.]An electrophorus is a metal discwith insulating handle.A Faraday Cage is an insulatedmetal cage. If charged, the charges onthe outside repel one another and get asfar away from one another as possible.to study attraction and repulsion beAn electroscope inside the cage will nottween charges (that is, between ball andget charged.charged bodies.) Neon Lamp helps detect presenceof electrical charges. The brightness ofits glow tells the intensity of electrostaticWhat is electricity? It is, as wefields. With the electrophorus you can know today, a flow of electrons betweengenerate, store and transfer small quanti- two points (of a conducting body) muchties of electrostatic charges. Electropho- like the flow of liquids from a higher torus consists of a metal disc with vinyl a lower level.What are electrons? They are tinyhandle and acrylic charge plate. Pith Balls are lightweight masses particles carrying an electric charge. Allthat you hang from strings and use for bodies contain electrons in their atoms.demonstrating repulsion from or attrac- Even though the electrons are chargedparticles, the atoms and the bodiestion to charged bodies. An Electro scope has vanes, a which they make up are normallypair of thin metal foil leaves sensitive to electrically neutral (uncharged.) Thiselectrostatic charges. They are connected is because each atom holds its electronstogether at one end to they spread apart revolving around a nucleus which con(re pel each other) or collapse (come tains an equal number of particles calledclose together.) The vanes are enclosed protons. Since protons carry the oppoin a 250 ml flask and are hung on 4 brass -site kind of charge as electrons carry,hooks by means of holes at one end. The the atom as a whole remains neutral orhanger connects to a short metal rod uncharged. Therefore the bodies arewhich passes through (and ends outside neutral or uncharged in their normalof) an insulating stopper that closes the state. Since by convention we think ofmouth of the flask. This permits the electrons as carrying a negative charge,metal ball terminal to be placed on the protons are electrically positive.Theory: Proof plane or Transfer Ball- flask stopper, so it is in direct contactto “move” charges from the generator with the rod end; or the metal disc ter-SCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/15Rods and ClothNeon LampProof PlaneElectrophorusWhat is static electricity?ConductiveBallPith Ball,suspendedMounted PointStand for CageFaraday Cage,point, coversIce PailAll matter is formed from positively charged nuclei and negativelycharged electrons. A body with possessequal numbers of positive and negativecharges is electrically neutral.A body which more negativelycharged electrons than positive chargesto complement them is electrically negative. A body with fewer negative chargesthan positive would be termed positivesince positive charges predominate.Except under rare circumstances, onlythe electrons flow. They flow away froma negative charge and toward a positivecharge.How does static electricitydiffer from currentelectricity?Static electricity resembles waterin a lake, current electricity resembleswater in a river. Provide a channel anda lake will flow as much as the channel permits and as long as the supplylasts.Static means to stand still. Staticelectricity is an electric charge whichremains stationary. Provide a channelfor its flow and it can become currentelectricity.Experiment 1:Friction GeneratesElectrical ChargesAdditional Items Needed: Lightweight materials(Paper, straw, feathers etc.)Kit Components Needed: Friction rods Friction surfacesFigure 1Procedure:1. Choose a friction road and surface(for example, acrylic rod andacetate cloth.)2. Cut out small bits of lightweightpaper (or straw, packing material,feathers etc.) and spread them onthe table.3. Hold one end of rod and rub theother end with fabric. (Figure 1)4. Bring rubbed end close to thematerial on the table.5. Watch the bits fly and stick to therod! Experiment with other rodsand surfaces.Further applications:Check out our websiteatwww.sciencefirst.comElectroscopeAssembly, flasksand terminalsDownload instructions,free articles, new productliterature and originalscience projects! Different students can usedifferent rods and surfaces.Compare cases! For older students, useuniform paper cut outs (from ahole puncher) in order to see ifthe rods pick up equal amountsof material when rubbed more. Plot a graph with the numberof paper pieces (Y-axis)againstthe length of time (or numberof rubs received.SCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/15Discussion:Why do rubbed rods behave thisway? Because the rods become chargedby friction and attract lightweight material electrostatically. See Experiment 3.How do the rods become charged?All matter has a fraction of its electronsin a relatively loosely held state. Whenbodies touch each other or come intoclose contact by rubbing, the surfaceelectrons from one body “get loose” andmove to the other surface. The bodies areno longer neutral; the one which gainselectrons is “negatively charged” andthe other body which has lost electronsis positively charged.Different materials have different affinities for gaining or losingelectrons. Silk gains electrons whenrubbed against glass and leaves it positively charged. Fur, flannel and woollose electrons and charge amber or hardrubber negatively.Frictional generation of electriccharges was how electricity was accidentally discovered by the ancientGreek philosopher Thales 25 centuriesago. He observed that amber (Elektron inGreek) attracted light material like strawand feathers after being rubbed with fur.He thought amber (electron) was lost inthe fur, but today we know that amberdraws electrons from the fur to becomenegatively charged.In generating electric charges, friction does not create more electrons.Electrons simply move between surfaces,keeping their total number the same.Electrons get redistributed and are notcreated or destroyed.Figure 2 -Attracting an Uncharged Body.Why does the rod attract the ball eventhough the ball is not charged? Thenegatively charged side, being closer to therod, is attracted by the rod more stronglythan the positive side of the ball is repelledby it.Experiment 2:Charged Bodies Can BeDischargedThe “shock” you get when touchinga doorknob or car door is because theseobjects are discharging the built-upcharge through you.Spark is discharge through ionizedair.Additional Items Needed:Experiment 3: Rods Pieces of paper, straw Metal surfaceLike Charges Repel;Unlike Charges AttractKit Components Needed: Friction rods Friction surfacesProcedure:1. Take the charged rod, touch withyour finger or to a metal surface (i.e.door knob.)2. Carry the rod to pieces of paper(or straw, feather etc.) as before. Usenew pieces of paper for best results!3. The rod now cannot pick up material. It has lost its charge.4. Compare cases using differentcombinations of rods and surfaces.In particular, use a positively chargedrod (glass rubbed against silk) and anegatively charged rod (acrylic rubbedagainst wool or fur.)5. Both kinds of charges can beremoved by discharging.Discussion:In charging, there is redistributionof electrons between two bodies so oneis positive while the other is negative.Discharging involves redistribution ofelectrons in which the charged bodiesbecome neutral.During discharge, electrons movebetween bodies through a transportingmedium. They use your body or doorknob to be transported - to the groundif your rod is negatively charged, orfrom the ground if positive.Certain substances are better transporters or conductors of electrons thanothers. Metals are good conductors. Therods and surfaces in these experimentsare not. They are insulators.There is electrostatic cling fromfriction when you rub against car seats,walk with shoes on carpets or in clotheswhen they rub against each other in adryer.Kit Components Needed: Charged RodsFishlineStandPith Balls(Procedure 3)Graphite Ball (Procedure 4)Electrophorus (Procedure 4)Procedure 1:1. Charge acrylic rod negatively byrubbing it against acetate cloth.2. Suspend it by a fishline or stringfrom a stand or high surface.3. Charge another acrylic rod negatively and bring its end nearthe charged end of the rod.4. Observe that the first rod swingsaway from the charged end of theother (Fig. 3). The two negativecharges repel each other.Figure 3 - A. 2 negative rods swingaway from each other B. Negativerod pulled toward positive. C.Positive rod pulled away frompositive. D). Positive rod pulledtoward negative.5. Bring positive rod (glass rubbedwith silk) toward charged end of suspended rod.6. Watch as it is pulled towardthe other. A positive charge attracts anegative one.SCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/157. Suspend the charged glass rodand bring another charged glass rodclose to the first one. They shouldrepel each other. Two positive chargesalso repel each other. Like chargesrepel while unlike charges attracteach other.Procedure 2:Perform the following variation:1. Instead of a charged rod, suspenda pithball (see Fig. 4)2. Bring a negatively chargedacrylic rod or positively charged glassrod close to it. Observe that the ball isattracted to the rod.3. Touch the ball with the rod.4. Watch the ball repel the rod.5. Move the rod close. You will bechasing the pith ball!now touches the first rod, it bounces offit too! You can actually keep the ball going back and forth between the two!Procedure 4:Show the same effects as in Procedure 2 by using the conductive ballinstead of the pith ball and an electrophorus in place of charged rods. SeeFig. 6.UnchargedBallBallinfluencedby chargedelectrophorusBallcharged byelectrophorusFigure 4Notemovementof ballNotemovementof ballFigure 6Procedure 3:1. Bring two rods, one of themcharged (either positively or negatively), the other uncharged, close to asuspended pith ball. (Figure 5)Approach it from opposite sidessimultaneously. (Uncharge pith ball bytouching it with fingers or wall beforeyou iscussion:This demonstrates several electrostatic properties. Attraction takes placebetween opposite charges and repulsionbetween like charges, as in Procedure1. The forces of attraction/repulsioncome from the electric field surroundingcharges (Fig. 7.)If an isolated electron is in the field,it would move towards the positive pole(charge concentration) and away fromthe negative pole.pith ball reorient themselves such thattheir electrons are closest to the positive end of the charged body (Fig. 8).In doing so they acquire the oppositeFigure 8charge.Subsequent to induction, there isattraction (between pith ball and rod)due to opposite polarity between them.When they touch, there is direct transferof electrons by conduction. The twobodies face each other with like chargesand therefore repel. The sequence induction, attraction, conduction and repulsion explains the bounding behaviorof the pith ball in Procedure 3.Advanced Concepts: Electrostatic attraction andreplication of a DNA molecule; thepassing on of genetic characteristics during cell division. Ionic vs chemical bonds.Experiment 4:Separating MixturesElectrostaticallyAdditional Items Needed: Salt and pepper PaperKit Components Needed: Acrylic charge plate Acetate clothProcedure:GlassFigure 52. Let the ball be attracted to thecharged rod. Then touch it.3. The ball will be repelled by thecharged rod, as before.4. Let the ball touch the other (uncharged) rod on the other side. Watchwhat happens. It bounces off. And if itFigure 7The experiments in Procedures 2and 3 demonstrate the concept of electrostatic induction, whereby a chargedbody induces an opposite charge inan uncharged body placed close to it.(Example - charged rod held close touncharged pith ball.) Molecules of the1. Spread mixture of salt and pepper(think of other combinations to use!)evenly on a sheet of paper lad flat.2. Place plate above paper, supportedon 2 blocks or books as in Fig. 9.3. Give a negative charge to theplate by rubbing its top with acetatecloth.4. Watch pepper particles jumpto the bottom of the plate (by induction and attraction), fall down (due tocontact, conduction and repulsion) andbounce up again.SCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/15MetalPlateAFigure 95. Cut out a paper piece in someshape (the number “8”, for example)and tape to the surface of the acrylicplate. Since the plate does not getcharged in the parts covered by thepaper figure, the pepper is finally attracted and held to the parts coveredby the figure.Discussion:This illustrates the principle of thephotocopier machine, where toner dustis attracted to the surface of a sheetof paper by electrostatic attractionand fixed by heating. Other examplesinclude: the filtering in air pollutiondevices; the illumination of TV monitor screens.To charge an electroscope:BCFigure 9 - An Electrophorus. A) Ametal plate lying on a negativelycharged surface. Electrons arerepelled to the upper surface of theplate. B) When you touch the plate, theelectrons escape from it. C) Lift thepositively charged plate. Bring yourfinger near it. You will get a spark.Experiment 5:Storing and TransferringElectrostatic Charges Electrophorus andProof PlaneKit Components Needed: Electrophorus Acrylic plate Neon lamp (optional)Procedure:Charge an electrophorus as in Fig 9.1. Rub plate with polyethylene soplate acquires negative charge. Placeflat on table.2. Holding electrophorus by handle,bring disc close to acrylic plate. Byinduction, the top acquires negativecharge (electrons reorient and aredriven to the top).3. Touch the top with a finger todischarge as electrons flow throughyour body.(See Figure 10.)Note: An electroscope detects andidentifies electrical charges. Presenceof charge makes its vanes diverge(due to similar charges acquired byboth). In the absence of charge, thevanes remain neutral and collapse.Note: You can show the discharge byusing the neon bulb. Hold one leadwith your finger and touch the disc topwith the other lead; the bulb will glowto show there is a charge flowing.4. Remove your finger. The dischas a net positive charge (fewer electrons.)5. Pull away disc from plate, holding it by handle.The electrophorus is positivelycharged.Note: You can place the disc onthe charged insulator plate in Steps2, 3 and 4. Contact is only at a fewmicroscopic projections to which theinsulator does not conduct electrons.Electrons on the insulator leak away.6. Transfer charges for different purposes from the “reservoir” of positivecharges built up in the electrophorus.Use a proof plane or transfer ball tocharge an electroscope Touch proof plane ball to disc. Itacquires a positive charge bycontact (conduction.) Move proof plane to electroscopeand touch ball to terminal. Vanes diverge due to the deposit ofpositive charge. You have used the proof plane totransfer positive charges. Can ittransport negative charges? Discharge proof plane by grounding it. Repeat with negativecharges. At first, the vanescollapse. Bring more charges, theydiverge. Why?Discussion:Figures 10 and 11 show the chargingof the electroscope with both positiveand negative charges done by conduction. The initial collapse of vanes is dueto neutralization of vanes by the negative charges you are depositing. Thesubsequent deposit of negative chargeswill make the vanes diverge becauselike charges were acquired.The proof plane in the experimentis physically transporting electrostaticcharges or static electricity.Static vs current electricity Anelectric current (or flow of electrons)along a conductor can be generatedby a perpendicularly moving magneticfield. Think of current electricity as theflowing water of a river, the generatorsas the water pumps and the wires as thewater pipes. By contrast, static electricity (that is, stationary charges) is likewater in a lake. Provide a channel andelectrostatic charges can also flow andbecome current electricity.Static electricity can be generatedusing mechanical means. Electrostaticcharges can be carried and moved aselectrons adhere to matter and go withthem. While an electric current can beSCIENCE FIRST 86475 Gene Lasserre Blvd., Yulee, FL 32097 800-875-3214 www.sciencefirst.com info@sciencefirst.com

2007 - v 4/15likened to the flow of liquids from ahigher to a lower level, moving chargesis like transporting liquids with dipperand pail.Experiment 6:Charge an Electroscopeby Induction.Kit Components Needed: Electroscope with assembly andflask Friction rodIntroduction:An electroscope detects the presence of an electrostatic charge by being“charged” by it.Try charging the elec troscope, firstwith a positive charge and then with anegative charge, as follows.Procedure:1. Fit one of the electroscopes witha ball terminal as sembly.2. Charge a glass rod positivelyby rubbing it with silk and bring thecharged (rubbed) end close to, but notin contact with, the ball terminal of theelec troscope.3. Observe the leaves of the electro scope diverge (go apart).4. Remove the charged rod awayfrom the electroscope terminal and ob serve the electroscope leaves collapse.5. Repeat the entire procedureabove, and obse

Electrostatic . Demonstration Kit Experiments . salt spray, chemical flames and perspi . Faraday Cage . is an insulated metal cage. If charged, the charges on the outside repel one another and get as far away from one another as possible. An electroscope inside the cage will not

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