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PHYS270

  • C5-14 ROCKET TRIKE

    C5-14
    Demonstrate Newton's third law of motion

    Pressing the fire extinguisher handle expels carbon dioxide out a nozzle straight behind the tricycle, causing forward thrust of the tricycle. Be sure the exhaust is not oriented to hit the audience or anything else likely to be adversely affected but a sudden blast of cold air.
    Background
    This is a dramatic illustration of Newton's Third Law of Motion: the principle of action and reaction. The mass of gas being ejected out of the back of the tricycle at a very high velocity imparts an equal and opposite force to the tricycle, which thus moves forward. The tricycle is much more massive, so it does not move as quickly, but the acceleration is still very real - be careful not to run into the wall!
    FS1

  • G3-01 SHIVE WAVE MACHINE - TRAVELING WAVES

    G3-01
    Demonstrates traveling waves

    Make sinusoidal waves by moving the spines at one end of the machine up and down sinusoidally, either with your hand or using the wave generator. Vary the amplitude and the frequency and observe the wavelength. You can show semi-quantitatively that the wave speed is approximately the same for all frequencies.
    Background
    The Shive wave machine illustrates transverse waves - the direction of displacement is perpendicular to the direction of transmission. This can be used as a model of many wave phenomena.
    FS0

  • G3-02: SHIVE WAVE MACHINE - SUPERPOSITION OF PULSES

    G3-02
    Demonstrate constructive and destructive interference using pulses.

    Starting identical pulses from both ends simultaneously, either in or out of phase, they can be observed as they pass. For two identical pulses, move your hand rapidly down and up at the center of the machine with the two ends fixed. The two pulses created will reflect off the ends (left photograph) and interfere constructively as they cross each other on their return (right). Repeat this with one end clamped to get a phase reversal of the pulse which reflects off that end.
    Engagement Suggestion
    • This is a good opportunity to bring up one or two volunteers from the class to participate, rather than trying to reach both ends simultaneously yourself.
    • Encourage the class to predict what will happen when the pulses pass each other.
    Background
    In a linear medium like this, two waves moving in opposite directions can be seen to pass through each other. The principle of superposition states that when two mechanical waves pass each other in a medium, the net displacement at any point is the sum of the individual wave displacements.
    Ofc

  • G3-03: SHIVE WAVE MACHINE - REFLECTION OF PULSES

    G3-03
    Demonstrate reflection of pulses from fixed ends and free ends.

    A pulse generated at the left end (photograph at left) reflects off the right end. The reflecting end can either be fixed (clamped, center photograph) or free (right photograph).
    Engagement Suggestion
    • Encourage students to make a prediction before each combination as to whether the wave will reflect, and whether that reflection will be upright or inverted. • This can be combined with demonstration G3-05, showing that fixed and free end reflections are the extreme cases of partial reflections due to a change in impedance.
    Background
    Like any wave in a transmission medium, when the medium ends the energy in the wave has to go somewhere. The wave is reflected back from the end. With a free end, the wave reflects identically; with the end clamped, it reflects inverted.

    g3-03 g3-03a g3-03b

  • G3-04: SHIVE WAVE MACHINE - STANDING WAVES

    G3-04
    Demonstrate standing waves.

    Standing waves can be generated with either (1) both ends fixed, (2) one end fixed and one end free, or (3) both ends free. You can use either your hand or the motorized drive; your hand possesses better feedback for small adjustments in frequency.
    A metronome is available upon request for comparing the frequencies of various harmonics, or you can time them using the classroom clock or computer.
    Engagement Suggestion
    • Ask students to make predictions before each configuration of the device. Will fixed ends, free ends, or one open and one free end have the longest wavelength fundamental?
    Background
    A standing wave oscillates in time, but the peaks do not travel in space. A standing wave can be created in a mechanical medium of fixed length with an oscillation at that medium's natural frequency, or a multiple thereof.

    g3-04 g3-04b g3-04d

    g3-04a g3-04c g3-04e

  • G3-28 SUSPENDED SLINKY

    G3-28
    Shows longitudinal and transverse traveling waves & standing waves
    Transverse or longitudinal pulses can be created by appropriate motion of your hand at one end of the SLINKY. Using your hand you can also create transverse standing waves and discuss the overtone series. Gently vibrating one end of the spring (either by hand or using the motor) at the appropriate frequency creates longitudinal standing waves.
    FS1

  • H2-21 AUDIBLE YOUNG'S EXPERIMENT - GROUP LISTENING

    H2-21
    Demonstrates interference of sound waves with two coherent sources
    The oscillator-amplifier is set to approximately 3000 Hz, with identical signals being applied to both loudspeakers. Rotating the loudspeakers past the listeners allows them to observe the interference pattern by hearing the alternating maxima and minima in the intensity pattern.
    OS2

  • H4-51: MODULATION - AM AND FM

    H4-51
    Demonstrate AM and FM signal modulation as an introduction to vibrato and tremolo.
    The Pasco Dual Function Generator is used to produce either amplitude modulation or frequency modulation using various combinations of sine, triangular, and square waves. Frequency modulation is pure vibrato and amplitude modulation is pure tremolo; actual vocal vibrato is a combination of pure vibrato and pure tremolo.
    H4, ME2

    h4-51ah4-51b

  • 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

  • J1-21 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

  • J4-32 DISCHARGE OF CAPACITOR WITH BANG

    J4-32
    Demonstrates that capacitors store electrical energy
    A 3500 microfarad capacitor is charged to 100 volts using the battery pack. Touch the capacitor terminals to the copper contacts on the battery pack; check that the polarity is correct, this is an electrolytic capacitor. Discharging the capacitor with the large screwdriver produces a very loud BANG.
    J4

  • J5-01 MAGNETIC FIELD OF A BAR MAGNET

    J5-01
    Visualize the magnetic field around a bar magnet
    A bar magnet is positioned beneath a plastic box on an overhead projector. Sprinkle iron filings into the box above the magnet and tap the box slightly so that the filings will align along the magnetic field lines.
    J5a, J5b

  • J5-04: MAGNETS

    J5-04
    Show various magnets
    A varied collection of magnets is presented, including bar magnets, horseshoe magnets, disc magnets, ring magnets, and rare earth magnets. Ask about other types of magnets.
    J5

  • J5-05: MAGNET MODEL - FIELD LINES

    J5-05
    Visualize the magnetic field of a bar magnet.
    A bar magnet is placed on an array of small compass needles on an overhead projector. The array of compasses maps out the magnet field of the bar magnet.
    J5

  • J5-06 MAGNET - BROKEN BUT NO MONOPOLE

    J5-06
    Demonstrates that magnet poles come in pairs
    The magnetic field of a bar magnet is demonstrated using iron filings on an overhead projector. The magnet is then broken and the demonstration is repeated. Each half of the original magnet has both poles
    J5

  • J5-11: MAGNETIC FIELD - EME SET - STRAIGHT WIRE

    J5-11
    Visualize the magnetic field around a straight wire.
    The magnetic field around a straight wire can be visualized by sprinkling iron filings in the area around where the wire passes through a plastic sheet which is positioned on an overhead projector. Alternatively, small compasses can be arranged around the wire.
    J5, PS1

    j5-11a

  • J5-13: MAGNETIC FIELD - EME SET - SOLENOIDS

    J5-13
    Visualize the magnetic field around a solenoid.
    Solenoids of three and seven turns respectively are wound through a plastic sheet. The magnetic field around either solenoid can be visualized by sprinkling iron filings in the area around where the solenoid passes through a plastic sheet which is positioned on an overhead projector. Alternatively, small compasses can be arranged within and around the solenoids.

  • J5-14 MAGNETIC FIELD AROUND SINGLE AND PARALLEL WIRES

    J5-14
    Visualize the magnetic field around a wire and near two wires carrying opposite currents.
    A large number of turns of small wire are used to produce a larger current, which passes through a plastic sheet on an overhead projector. Two current sources are available on this one: a single wire and two nearby wires with equal but opposite currents. Sprinkling iron filings on the plastic sheet near the wires and gently tapping the sheet causes the filings to line up along the magnetic field lines
    J5, PS1

  • J5-15: MAGNETIC FIELD OF A RING OF CURRENT - MODEL

    J5-15
    Model the geometry for the magnetic field along the axis of a ring of current
    This is three-dimensional visual model of the magnetic field of a ring of current. Vector current elements on opposite sides of the ring of current are shown along with vectors extending from the current elements to the point on the axis at which the magnetic field is to be determined. The two magnetic field vectors created by the two elements of current are perpendicular to both the current elements and to the radius vectors. The radial components of the vectors cancel, but the two axial vector components add, forming the net axial field vector shown in the model.
    J5b

  • J5-16 MAGNETIC FIELD OF WIRE, LOOP, SOLENOID

    J5-16
    Visualize magnetic field lines for simple current configurations

    A portable power supply and switch mechanism are used to provide a brief, strong current through any of three transparency-mounted conductor configurations. Connect current leads to the conductor configuration desired; single wire, single loop of wire, and multiple-turn coil are available. While current is on, sprinkle iron filings on plastic sheet passing through the sample and gently tap the plastic sheet to make the iron filings align along the magnetic field lines.

    For safety and to preserve the lifespan of the apparatus, do not turn current on for more than a second. Please be careful not to touch leads or conductors while current is on.
    J/K