Description
Produce net charge by rubbing a rubber rod with a piece of rabbit fur; or an acrylic rod with cellophane; or a glass rod with silk. Use an electroscope as a charge indicator.
NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Alternate: Instead of the rubber rod, use a piece of amber.

Equipment
PVC Rod, felt, rubber rod, rabbit fur, Acrylic rod and/ or cellophane; Gold leaf electroscope, probe electroscope and/ or overhead electroscope
Support Equipment
Overhead projector for the overhead electroscope

Description
Remove, by finger touch, excess charge from a metal paddle that is in contact with a statically charged acrylic sheet.
1. Rub insulating stand's acrylic sheet with rabbit fur. (Acrylic sheet becomes negatively charged. This static charge does not move around or off of plate during demonstration due to the insulating nature of the acrylic. On humid days, the negative charge will "leak off" of acrylic sooner than desired.)
2. Holding metal paddle with its insulating handle, place paddle in good contact with acrylic sheet. (Acrylic's negative charge repels metal paddles electrons to the top of the paddle. Metal paddle will still have a overall net neutral charge.)
3. Touch the top of the metal plate with finger. (Negative charge, electrons, will move off of plate on to you, the ground. Plate is left with a net positive charge, a deficit of electrons.)
4. Remove finger, remove the now positively charged plate.
5. Optional: to have students "observe" the net charge on the paddle:
- bring paddle in proximity of/ or in contact with an electroscope
- bring paddle in proximity of/ or in contact with a student's hand
6. The metal paddle can be recharge multiple times without "rerubbing" acrylic sheet. The acrylic sheet's static charge is not removed by this procedure.
NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Web Simulation:
Charging an Electrophorus by Induction Using a Negatively-Charged Object
http://www.physicsclassroom.com/mmedia/estatics/epn.html

Equipment
Induction Paddle, Insulating Stand w/ acrylic top sheet, Rabbit Fur

Coulomb's Law: Electrostatics
Rods & Pivot
PIRA Class: 5A20.10

Purpose
To demonstrate like charges repelling and unlike charges attracting.

Description
With one charged rod on a pivot, use another rod of the opposite or same charge to show attraction or repulsion.
NOTE:
- This demo may not work on a humid day.
NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Equipment
Glass & rubber rods, silk & rabbit fur, & nylon thread
Support Equipment
Small stand

Description
Suspend two small, similarly charged pith balls and observe that they repel each other.
Pith balls are covered with a conducting material. (Aluminum foil or graphite spray paint)
1. Hang pith balls side by side, touching.
2. Rub down rubber rod with fur, rod will acquire a negative charge.
3. Carefully slide charged rod over one of the pith balls to transfer over as much negative charge as possible.
4. Since pith ball surfaces are conducting and in contact with each other, negative charge will spread out uniformly over both surfaces, and in turn repel each other.

NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.
ALTERNATES:
- Use glass rods rubbed down with a piece of silk. (Glass rods will lose electrons in the process.) When gently sliding glass rod over  the pith ball, electrons from the pith ball will transferred to the positively charged glass rod and pith ball will gain a net positive charge.
- Use two balloons, one hanging and the other handheld. Charge (negatively) with fur. Balloons will be statically charged and will not transfer charge from one to the other by contact.

Web simulation:

Equipment
Pith balls, fur, rods
Support Equipment
Small stand

Description
By direct contact of charging by induction, use light weight gold leaves within the electroscope to indicate the relative amount an object is charged. Leaves will spread out more and more as they gain more and more charge, whether positively or negatively charged.
- Charging by induction: Place the object near to the electroscope, the electroscope top knob will acquire the opposite charge of the object at hand. Strips will then have the same charge as the object. (Object's net charge is not changed during this process.) The closer the object is brought to the top knob, the greater the separation of charge within electroscope, the greater the separation of the gold leaves. Move the object away from electroscope and electroscope charges will redistribute 'evenly' about, and leaves will return to original position.
- Charging by contact: Bring the object in contact with the top knob of the electroscope, charge can then transfer from object to the electroscope and its gold leaves. Leaves separate, this separation distance will depend on the amount of charge transferred. Remove object from electroscope, charged leaves will remain separated.

NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Web Simulation: 
Charging an Electroscope by Induction Using a Negatively-Charged Balloon
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/estatics/esn.html

Equipment
Gold Leaf Electroscope, charged object
Support Equipment

Description
By direct contact or charging by induction, observe the relative charge of a charged object. Needle will register according to the relative measure of net charge present, whether positive or negative.
- Charging by induction: Placing the object near to the electroscope, the electroscope  knob will acquire the opposite charge of the object at hand. Needle will then have the same charge as the object. (Object's net charge is not changed during this process.) The closer the object is brought to the knob, the greater the separation of charge within electroscope, the greater the register of the needle. Move the object away from electroscope and electroscope charges will redistribute 'evenly' about, and needle will return to original position.
- Charging by contact: By bring the object in contact with the   knob of the electroscope, charge can then transfer from object to the electroscope. Needle register will depend on the amount of charge transferred. Remove object from electroscope, and electroscope will remain charged.
NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Web Simulation: 
Charging an Electroscope by Induction Using a Negatively-Charged Balloon
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/estatics/esn.html

Equipment
Projector Electroscope, charged object
Support Equipment
Overhead Projector

Description
Induced charge is used to rotate a long 2"x4" wood board balanced on a watch glass.
1. Balance a long 2"x4" board on a watch glass that has been placed on a stool in front of the class.
2. Have two students (one standing at each end of the balanced board) charge up their respective balloon using a piece of rabbit fur.
NOTE: Students could use the old fashion method of rubbing balloon on their hair, but hair styling gels, etc. will interrupt the transfer of negative charge from their hair to their balloon.
3. Have students position balloons on opposite sides of the board: near to the board, but not touching the board (see figure).
4. As board starts to turn to the balloon, instruct student to slowly, and continually move the balloons away from board. Board's rotation speed will actually increase as the balloons exert their respective torques.
NOTE: Negatively charged balloons induce a positive microscopic surface charge on the nearby board. Opposite charges will attract each other, i.e. exert forces of attraction on each other's masses.
VARIATION: Charge up a balloon and have it statically cling to the wall.

Equipment
watch glass, balloons, 6-8 foot long 2"x4" board
Support Equipment
Stool

Description
Crank a Wimshurst generator to produce large amounts of stored charge. Negative charge will be removed to one side of the generator, leaving other side positively charged. Using this generator is a good fall back for electrostatic demonstrations on humid days.
NOTE:
- Remind students that the overall net charge of generator remains zero.
- Use high voltage wire leads (labeled "Wimshurst leads") to transfer charge to objects
- Take care not to touch any metal portions of the generator.
- Bring Wimshurst "arms" close to each other, but not touching, to observe discharging. On days of low humidity, this discharge could be as long as 3 cm.

Equipment
Wimshurst machine, Small/ Large; High voltage "Wimshurst" leads
Support Equipment

Description
Show the electric discharge from Van de Graff generator to a nearby grounded rod.

Beforehand:
-On the day before / week prior to your classroom demonstration, make sure Van de Graff control box is plugged in and heater is turned on. This will reduce moisture within the Van de Graff.
-Check the base's desiccant stores. If desiccant is pink instead of blue, it needs to be replaced (or dried out in a 400 oven for 12 hours.)
- If during trial run no discharge is produced (and all connections, etc. are in order), securely attach a grounding lead from dome to base (with duct tape) and run belt motor for ~30 minutes. (No HV!) This will help remove excess humidity from inside dome.

1. Locate Van de Graff in classroom 5 feet away from any student/ student desk/ classroom electronics/ etc.
2. Make sure grounding rod and control box connections with Van de Graff base are secure.
3. While holding grounding rod pole in one hand, flip on belt motor at control box with the other.
4. Flip on HV (high voltage) at control box. Bring grounding rod close to dome to observe discharge.
5. To turn off Van de Graff, turn off High Voltage first and then the belt motor. Once belt is no longer moving, touch grounding rod to dome one last time to insure that dome is completely discharged.
NOTE:
- Depending on the day's humidity, discharge will be small or large.
- Internal belt and brushes remove electrons from Van de Graff dome, leaving dome positively charged. When brought in close contact, grounding rod replaces these negative charges; belt immediately strips them off again.
- Dome's potential will reach ~20,000V with respect to grounding rod.

Web simulation:

Equipment
Van de Graff generator, control box and grounding rod

Description
Standing on an insulated stand with one hand on a Van de Graff generator, long hair can be observed to fly radially outward.

Beforehand:
-On the day before / week prior to your classroom demonstration, make sure Van de Graff control box is plugged in and heater is turned on. This will reduce moisture within the Van de Graff.
-Check the base's desiccant stores. If desiccant is pink instead of blue, it needs to be replaced (or dried out in a 400 oven for 12 hours.)
- If during trial run no discharge is produced (and all connections, etc. are in order), securely attach a grounding lead from dome to base (with duct tape) and run belt motor for ~30 minutes. (No HV!) This will help remove excess humidity from inside dome.

In Class:
1. Locate Van de Graff in classroom 5 feet away from any student/ student desk/ classroom electronics/ etc. (Van de Graff has been seen to fry a computer's muse board. That's right, Fried Mice in class!)
2. Make sure grounding rod and control box connections with Van de Graff base are secure.
3. Choose a pace-maker free student with oil-free, relatively well groomed, med./ long hair. Have student remove any metal objects/ jewelry, especially from the side of their body that will be closest to Van de graff. (Small earrings are ok; Van de Graff has been known to discharge to students' metal shoe buckles.)
4. Have student stand on insulating stand and place one or both hands firmly (and flatly) of Van de Graff dome. (Inform student that if they remove their hand from the dome at any time durin the demonstration, they should not put it back on the dome.)
5. While holding grounding rod pole in one hand, flip on belt motor at control box with the other.
6. Flip on HV (high voltage) at control box. Observe hair to stand on end, illustrating the electric field about the student's head.
7. To turn off Van de Graff, turn off High Voltage first and then the belt motor. As student's hair falls back down, have student remove hand. Once hair is fairly "back in Place", student may step off of insulating stand. By rubbing shoulders with another, most excess charge will be removed.
8. Before moving Van de Graff aside, touch grounding rod to dome one last time to insure that dome is completely discharged.
NOTE:
- Depending on the day's humidity, discharge will be small or large.
- Internal belt and brushes remove electrons from Van de Graff dome, leaving dome positively charged. When brought in close contact, grounding rod replaces these negative charges; belt immediately strips them off again.
- Dome's potential will reach ~20,000V with respect to grounding rod.

PEDAGOGY: Remind students that excess charge distributes itself all over dome and student alike. Each strand of hair will have this same charge (positive). Thus, the strands of hair repel each other

Equipment
Van de Graff generator, control box and grounding rod; Insulating Stand, Student w/ long, oil-free hair

Description
See the 'eruption of salt' from the surface of a Van de Graff upon the generation of static

Equipment
Van de Graff generator, control box and grounding rod; Salt packages

Description
Confetti (puffed wheat, Styrofoam peanuts) flies off the dome of the Van de Graff generator.
See Demo: 5A50.30 Van de Graff Generators for demo preparation and operation
ALTERNATE: Use Vanessa Van de Graff's wig or student's hair to illustrate the field lines.

Equipment
Van de Graff generator, control box and grounding rod; Confette, puffed wheat, Styrofoam "peanuts", or Vanessa Van de Graff wig

Description
A fountain spray of water can be created when a charged rod placed near a water stream jetting upward.

Equipment
Rod & Fur, Eye Dropper & Hose Jet

Description
Bermuda seeds suspended in oil display electric field lines about a round object and a square object.
- Attach leads from Wimshurst to the Field Visualizer situated on overhead projector.
- Separate discharge arms on Wimshurst and crank it up. NOTE: During this demo, all metal parts, visualizers included, are highly charged, take care in handling this equipment.
- Observe the action of the burmuda seeds:
     * Burmuda seeds are initially attracted to metal portions by charge induction.
     * Upon touching either side, individual seeds acquired the charge of that respective side and is subsequently repelled by that side and attracted to the other (oppositely charged) side.
     * Some "seed charge bridges" are formed from one side of the visualizer to the other.
     * For the visualizer with the center rectangular "terminal", note the difference between the field line densities at the rectangle ends vs. sides.

Equipment
Med. Wimshurst, high voltage leads, Field Visualizers
Support Equipment
Overhead projector

Description
With a proof plane and electroscope, show charge is on the outside of a hollow conductor.

Equipment
Faraday Ice Pail
Support Equipment

Description
Charged pith ball is lowered in to 'Ice Pail', charge is observed on an electroscope.

Equipment
Faraday Ice Pail

Description
With peanuts in the metal cup on top of the Van de Graff, turn on Van de Graff; repeat w/ peanuts inside Styrofoam cup.
See Demo: 5A50.30 Van de Graff Generators for demo preparation and operation
- Peanuts within metal cup stay charge free, "protected" by the metal cup.
- Peanuts within Styrofoam cup (or plastic beaker) acquire a net charge, and dramatically fly out due to the force of the electric field.
NOTE: Do not reuse Styrofoam peanuts. The net charge that they acquire is very difficult to remove and they end up statically clinging to plastic containers that they are put back into. Rinse out synthetic cups with water to remove any excess charges before reusing synthetic cups.

Equipment
Metal cup, Styrofoam cup & peanuts (discharged)

Support Equipment
Van de Graff Generator

Description

Equipment
Carbon Arc

Support Equipment
Power supply, wire connections

Description
A pinwheel connected to a Wimshurst machine turns due to the like polarity of the points and their corona discharge.

Equipment
Electrostatic pinwheel on stand
Support Equipment

Description
A discharge tube is illuminated due to the electrostatic potential generated by the Van de

Equipment
Discharge tube
Support Equipment
Van de Graff generator

Description
Change the spacing of a charged parallel plate capacitor while it is attached to an

Equipment
Parallel Plate Capacitor Demo
Support Equipment
Med. Wimshurst

Description
Insert & remove a dielectric from a charged parallel plate capacitor while it is attached to an electroscope.

Equipment
Parallel Plate Capacitor Demo, Acrylic and wood boards
Support Equipment
Med. Wimshurst

Description
Wooden balls are rolled down a ramp with nails. The slope of the incline can represent the applied E.M.F.
NOTE: To insure that balls roll freely down board and not get "stuck" on the side nails, be sure to have the board end marked "TOP" elevated.

Equipment
Orange (golf or wooden) balls
Support Equipment
Resistance Model Board

Description
A pencil lead and its drawn line are part of a simple circuit. As the line is drawn longer and longer, the resistance of this circuit is observed to increase, or alternately the current is observed to decrease.
1. Connect (in series) a 6 volt battery, a high graphite art pencil, a thickly drawn line (~3 cm. long), and a multimeter set up to measure resistance.
2. Extend the length of the line while observing the change in the circuit's resistance.
ALTERNATES:
- To demonstrate a conductor's width and resistance inverse proportionality, double the thickness of the line and the resistance will decrease
- Draw (curved) lines side by side to demonstrate how parallel circuits will generally have decreased resistance.
NOTE: The thickness and width of these hand drawn lines is difficult to control. Do not expect multimeter readings that can quantitatively compared.

Equipment
Very soft graphite Pencil
Support Equipment
Ohmmeter

Description
A circuit's wire coil is dropped into liquid nitrogen and a subsequent drop in the circuit resistance is observed. An increased in the circuit's resistance is observed when the same

Equipment
Wire coil, Light Bulb
Support Equipment
Power Supply, Overhead projector, liquid Nitrogen, Heat source

Description
With the room lights off, watch a pickle glow and sizzle when hooked up to a 110 V outlet.

Equipment
Cord with Nail Prongs, Pickle
Support Equipment

Description
Electric discharge climbs with rising ionized air.

Equipment
Jacob's Ladder
Support Equipment

Description
Measure current and voltage in a simple circuit. Change the voltage or resistance.

Equipment
Ohm's Law Unit for Overhead Projector
Support Equipment
Overhead Projector

Equipment
Ohm's Law Board
Support Equipment

Description
Identical light bulbs are connected in various series and parallel connections and their relative brightness is predicted by the students before the circuit is closed.

Equipment
Lamp Unit
Support Equipment
Power supply

Description
A light bulb board with switches and lead wires allows for several combinations/ configuration of series and parallel lightbulbs.

Equipment
Series & Parallel Lightbulb Board, Lead wires
Support Equipment
110/ 120 V outlet

Description

Equipment
Support Equipment

Equipment
Assorted magnets, Rotating Magnet Stands, Iron Filings
Support Equipment

Description

Equipment

Support Equipment

Description
Students are given a magnet and a non-magnet and asked how they can determine which rod is the magnet.

Equipment
Two identical rods: one magnet & one non-magnet
Support Equipment

Description
An array of small compass needles illustrates the domain structures within a ferromagnetic material.

WARNING: Many students already confuse the north and south poles of a magnet to be positive and negative charges (respectively!). This apparatus reinforces this misconception!!!

Equipment
Magnetic Domain Model; small, strong magnet
Support Equipment

Description
Use a compass and/ or several compasses to investigate the field lines about a magnet.

Equipment
Magnet, compass
Support Equipment

Description

Equipment
Dip Needle
Support Equipment

Description
Show the magnetic field lines about a bar magnet.

Equipment
Rectangular bar magnets, glass sheet, Iron filings, tray (or 2-D Magnetic Field Demonstrator)
Support Equipment
Overhead projector

Description
Show magnetic field lines in all 3 dimensions about pole ends: Like and Dislike Poles

Equipment
Pair of cylindrical bar magnets, 3-D Magnetic Field Demonstrator
Support Equipment
Overhead projector

Description
To show the magnetic field about a current carrying wire with: I. Wire pacing through the center of 3D magnetic field demonstrator II. Wires wrapped around the 3D Mag Field

Equipment
3-D Magnetic Field Demonstrator, compass
Support Equipment
Power supply, Overhead projector, Wire

Description
Use several mini compasses to 'see' the magnetic field lines about a current.

Equipment
Minicompasses
Support Equipment
Power supply, Overhead projector,

Description
Observe the magnetic field lines about a solenoid.

Equipment
Solenoid board, iron filings
Support Equipment
Power supply, Overhead projector

Description
To show the repulsion force between like poles.

Equipment
Linearly levitating magnets
Support Equipment

Description
Use a magnet to deflect an electron beam.

Equipment
Crooke's Tube (CRT)
Support Equipment

Description
A beam of free electrons is bent into a circular/ spiral path by large Helmholtz coils.

Equipment
e/m tube, power supply and lead wires
Support Equipment

Description
Trigger the current through a wire, that is between the pole faces of a large magnet, on and

Equipment
Jumping Wire
Support Equipment
Lg. magnets (part of Lenz's pendula), power supply

Description
Small coil of wire connected to a C battery spins on its own over a magnet

Equipment
World's Simplest Motor
Support Equipment

Description
Compare the galvanometer readings for different solenoid turns and direction of current flow.

Equipment

Support Equipment

Description
Induce currents of varying magnitude by passing a magnet back and forth through different coil wraps.

Equipment
10/20/40 unit, magnet
Support Equipment
Power supply, Overhead projector

Description
Swing a large coil of wire through the magnetic field of the earth.

Equipment
Earth Inductor, Lecture room galvanometer
Support Equipment

Description
Swing solid metallic pendulum paddles between poles of a magnet. Slots in otherwise identical paddles prevent the circulation of the eddy currents.

Equipment

Support Equipment
Lenz's Law Pendulum

Description
To observe the opposing induced magnetic field's effect on a magnet falling through a

Equipment
Spring scale, magnet, dummy magnet
Support Equipment
Two 1.5 m Aluminum tubes

Description
Faraday Magnetic Field Effect

Equipment
Jumping ring accessory set

Support Equipment
Vertical Transformer

Description
Slowly wind a wire connected to a small light bulb around a vertical transformer.

Equipment
Light bulb on a board
Support Equipment
Vertical Transformer

Description

Equipment

Support Equipment

Description
Students observe the rotation of a Coil of Wire over a magnet

Equipment
World's Simplest Motor

Support Equipment

Description

Equipment
4.5 V maximum motor
Support Equipment

Description
Hand crank a current to light the lightbulb.

Equipment

Support Equipment

Description
Pass the basket of old transistor tubes about the class.

Equipment
Transistor Tube Basket

Support Equipment

Description

Equipment

Support Equipment