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Electrostatics

  • J1-01 TRIBOELECTRICITY - CHARGING BY FRICTION

    J1-01
    Demonstrates "charging by friction"
    Rubbing silk on a glass rod makes the glass positive and the silk negative. Rubbing fur on a hard rubber rod makes the hard rubber negative and the fur positive. This effect is known as "triboelectricity," from the Greek "tribein," or to rub. The positively charged glass rod and the negatively charged hard rubber rod can then be used (1) simply to illustrate that electrical charge exists using an electroscope or (2) to perform other electrostatics experiments.
    J1b

  • J1-02: TRIBOELECTRICITY - WATER JET IN AIR

    J1-02
    Illustrate triboelectricity.
    A water jet falls from a reservoir through a small opening and falls into a receptacle can which is electrically connected to an electroscope. The source reservoir is ungrounded and can be shown to be electrically neutral at the beginning of the experiment. The water stream breaks up as it falls, charging the the water droplets falling into the pan, which can be seen from the electroscope. Charging materials may be used to ascertain the sign of the charge on the electroscope, if desired.

  • J1-03 KILOVOLT CARPET

    J1-03
    Demonstrates "charging by friction"
    Connect one end of the fluorescent tube to the grounded cable. Hold the other end of the tube as you scuff your shoes on the carpet.
    J1b

    J1-03-KILOVOLT-CARPET

  • J1-05 CHARGED BALLOONS

    J1-05
    Demonstrates "charging by friction"
    Rub a balloon on your clothing to give it electrical charge, then stick it on the blackboard, wall, etc. This is essentially the same triboelectric effect as J1-01, but with materials more familiar to students.

    Note that the backplane shown in the photo is for illustrative purposes; most classrooms have walls that work just fine.
    J1b

  • J1-06: FUN-FLY-STICK

    J1-06
    Demonstrates electrostatic fundamentals
    This is a battery operated static electricity generator that allows you to float tinsel shapes above the electrically charged stick. Since like charges repel each other, the negatively charged tinsel floats above the negatively charged stick.
    J1b

  • J1-11 ELECTROPHORUS

    J1-11
    Demonstrates an electrophorus
    An electrophorus is a device which retains its charge so that it can act as a continuing source of charge for experiments. Charge the acrylic electrophorus plate negative by rubbing it with fur. Placing the aluminum plate on top of the plastic plate and grounding it charges the aluminum positive by induction. Existence of these charges can be verified using the electroscope. The charge remains on the surface of the plastic plate, so the aluminum plate can be charged by induction a number of times before the charge on the plastic leaks away
    J1b

  • J1-12: INDUCTION - ELECTROSCOPE

    J1-12
    Demonstrate charging by induction.
    A charged rod (black rubber in the photograph is negative) is held near the top plate of the electroscope, causing the electroscope to deflect. While the rod is in this position, the plate is touched by a grounded banana wire, and the electroscope returns to the uncharged position. When the charged rod is pulled away, the electroscope is charged positive, and deflects. This experiment can also be done using a positive glass rod to charge the electroscope negative by induction. The sign of the charge on the electroscope can be checked as follows: a rod with the same charge as the electroscope will cause further deflection of the electroscope when held close to the top plate, but a rod with charge opposite that of the electroscope will cause less deflection of the electroscope when brought close to the plate.
    J1b

  • J1-13: ELECTROSTATIC INDUCTION

    J1-13
    Illustrate charging by induction.
    Run the Van de Graaff for a couple of seconds to develop a small charge on the dome, then turn it off. Hold the two plates touching each other near the dome (but do not draw a spark) with one closer to the dome and one further away. While the plates are near the dome, separate the two plates and then remove them from the area of the dome. The two plates will be equally but oppositely charged, as can be verified using the electroscope.
    J1a, J1b

  • J1-14: Electrostatic Induction - Attracting a Can

    j1-14
    To illustrate electrostatic induction and the force between charged objects

    Place a dry, empty aluminum soda can on the table. Build up a charge on one of the charging rods and hold it alongside the can, and you should see the can move slightly towards the rod; with a strong enough charge, you can pull the can across the table via the attraction to the rod. The charge on the rod is inducing an opposite charge on the side of the can.

    Now, pick up the can, and ask the students to predict what will happen if you do the same thing with the other rod and an opposite charge. Poll them for their predictions, and the reasons behind them. Then put the can down and perform the experiment again with the other rod; you should see the same behaviour. Invite the students to discuss why this happened. The can was grounded when you picked it up, and retains no net charge on any side; the induction process is the same as before.

    Note that this is the same effect that causes the ground sphere to slowly lean towards the Van de Graaff generator before a spark forms in demonstration J2-03.

    J1b, SU14

  • J1-21 ELECTROSTATIC ATTRAC AND REPULS - CHARGED CYLINDERS

    J1-21
    Demonstrates electrostatic attraction and repulsion
    Charge the glass cylinders positive by rubbing with silk, and charge the hard rubber cylinder negative by rubbing with fur. The two positive glass cylinders repel each other, but both are attracted to the negative hard rubber cylinder.
    J1b

  • J1-22 ELECTROSTATIC ATTRAC AND REPULS - WIMSHURST MACHINE

    J1-22
    Demonstrates electrostatic attraction and repulsion
    Two conducting balls suspended from the two arms of the Wimshurst machine are oppositely charged and attract each other. The same two balls suspended from a single arm of the machine will repel each other.
    J1a

  • J1-23: ELECTRIC CHIMES

    J1-23
    Demonstrate electrostatic forces.
    A small ball is suspended between two bells, which are in turn electrically connected to the two sides of a Leyden jar capacitor. When the capacitor is charged, the ball oscillates between the two bells.

    This demonstration can build up significant charge; please handle carefully.
    J1a

  • J1-24 ELECTROSTATIC HAIR RAISING

    J1-24
    Demonstrates electrostatic repulsion
    While standing on a large styrofoam insulating block, touch your hands to the top of the Van de Graaff dome, then have someone turn it on. The fact that your hair stands on end is a result of the repulsion between charges of the same sign that collect on your hair.
    J1a, OS2

  • J1-25 VAN DE GRAAFF - TRAINED RABBIT

    J1-25
    Demonstrates electrostatic repulsion
    A piece of fur, the "rabbit," is placed on top of the Van de Graaff dome, and a grounded point is held adjacent to the dome as the Van de Graaff is turned on. Pull the point back, allowing the dome and fur to charge, while ordering the rabbit to "sit up." Move the point closer to the dome while ordering the rabbit to "sit down."
    J1a, J1b

  • J1-26 VAN DE GRAAFF - REPULSION OF PIE PANS

    J1-26
    Demonstrates electrostatic repulsion

    A group of aluminum pie pans is placed on top of the Van de Graaff dome and the Van de Graaff is turned on. The pie pans are pushed off the top of the dome one at a time by the electrostatic repulsion. Use this as a way to argue that electrostatic forces might be stronger than gravitational forces.

    Engagement Suggestion:
    • Before turning the generator on, encourage students to predict what is going to happen. Challenge them to explain their hypotheses in terms of what they have learned about the behaviour of electrical charge.
    • Feel free to invite students to collect the scattered pans, but remind them not to get close to the Van de Graaff while it is turned on.
    J1a

  • J1-27: QUALITATIVE EXISTENCE OF ELECTROSTATIC FORCES

    J1-27
    Demonstrate the existence of electrostatic forces.
    The Van de Graaff is first turned on, charging the dome, and the ground sphere by induction; sparks between them indicate the existence of high voltages. The Van de Graaff is then turned off, and conducting aluminum foil cylinders hanging from strings are inserted between the dome and the ground sphere. The cylinders move back and forth between the dome and the ground sphere, demonstrating the existence of electrostatic forces.
    J1a, FS2

  • J1-29: VAN DE GRAAFF - PENDULUM

    J1-29
    Demonstrate electrostatic force.
    A pendulum isolated by a wooden vertical support is placed on top of a Van de Graaff. The pendulum bob becomes charged, experiences a repulsive force from the dome, and moves about erratically. Try other lengths to get different motion.
    J1a, FS2

  • J1-41: CONDUCTORS AND INSULATORS

    J1-41
    Demonstrate the difference between materials that conduct electricity and those that do not.
    Two electroscopes are charged with equal and opposite charges. The electroscopes are then connected by a clean rod of acrylic (left), that does not conduct, and of metal (right) that will discharge both electroscopes when it contacts both.
    J1b

    j1-41a

  • J2-01: WIMSHURST MACHINE

    J2-01
    Generate high electrostatic potentials.
    Cranking the handle rotates the two plates in opposite directions, generating a large electrostatic potential. The Leyden jars can be charged to increase the intensity of the spark between the two balls on the arms mounted above the Leyden jars. This machine can also be used for other demonstrations requiring high potentials. This gizmo may go up as high as 500,000 volts.
    J2a

  • J2-02: KELVIN ELECTROSTATIC GENERATOR

    J2-02
    Demonstrate the Kelvin electrostatic generator.
    This device generates electrostatic charge from the breakup of a water stream. The water stream is split and directed downward simultaneously through two cylindrical metal shells into two receptacle cans. Wires connect the shell of one side to the bottom can of the other side to provide positive feedback for the generation of high potentials. One of the cans is connected to an electroscope, to indicate the presence of an electrostatic potential. After a few seconds of dripping, sufficient voltage is developed to deflect the water droplets away from the receptacle cans. A grounded stop on the electrometer discharges the system and the cycle restarts.