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PHYS121

  • F4-01: VISCOSITY OF LIQUIDS

    F4-01
    Compare the viscosities of water and mineral oil.
    Two tubes contain heavy balls in water and mineral oil, respectively. Invert the tubes and compare terminal velocities to compare viscosities.
    OS4

  • F4-11: LAMINAR AND TURBULENT FLOW OF AIR

    F4-11
    Demonstrate laminar and turbulent flow.
    Place the streamers near the front of the fan, and notice that they line up due to the laminar flow. Then place the streamers behind the fan or about one meter away, and note that they move irregularly due to the turbulent flow.
    F4, OS6

    f4-11a

  • F5-21 VENTURI TUBE WITH MANOMETERS

    F5-21
    Illustrates the venturi effect
    Turn on the blower and slowly move it so that it directs some air into the venturi tube device. The higher water level indicates less air pressure in that tube.

  • I1-01: THERMOMETERS

    I1-01
    Show several types of thermometers.
    Several thermometers, as photographed above, just lie there reading the temperature. You must plug in the electronic one and turn it on.
    I1, I0

  • I1-11 THERMAL EXPANSION - BALL AND HOLE

    I1-11
    Illustrates thermal expansion
    At room temperature the ball will not fit through the hole in the metal plate. When the plate is heated by a burner for about 30 seconds, the ball easily fits through the hole
    I1, I0

  • I1-13 THERMAL EXPANSION - BIMETAL STRIP

    I1-13
    Demonstrates differential thermal expansion

    Two strips of different metals, invar steel and brass, are welded together to form a bimetal strip. Since each metal has a different coefficient of thermal expansion, heating the bimetal strip will result in the metals expanding at different rates, causing it to bend.

    When heating, always wear goggles and handle the flame with care, ensuring that it is not pointed near students or flammable materials. Use in a well ventilated classroom.

    Engagement Suggestion
    Ask your students: • Which metal will expand more when it is heated, and why?
    • What happens when it is cooled?
    • How could you make use of this to measure or control something?
    Background

    The amount a metal expands or contracts with temperature is governed by its coefficient of thermal expansion, a property which varies between different metals depending on their molecular structure. Invar steel is an alloy designed to have an exceptionally low coefficient, about one-tenth that of most steel, while brass has a higher coefficient than even ordinary steel. So the brass expands much more rapidly than the steel does when heated.

    Bimetallic strips like this are used in some types of thermometers and thermostatic controllers (including many older window thermometers and household thermostats). Check out demonstrations I1-17 and I1-18 for examples and to see how this works.
    I1, I0

  • I1-63: HYDROGEN EXPLOSION

    I1-63
    Produce a hydrogen explosion

    A balloon filled with hydrogen is tethered about six feet above head level. The burning match on a stick is positioned under the balloon, creating the hydrogen explosion.
    Engagement Suggestion
    • One option for presenting this would be to compare the behaviour of two different balloons, hydrogen and helium. You can tell students what is in each balloon and have them make a prediction about what each will do, or show the demonstration first and then have students analyze why the results were different.
    I1, I0, FS1

    I1-63B

  • I2-06 THERMOPILE WITH AUDIO OSCILLATOR

    I2-06
    Observe infrared radiation
    The output from a commercial thermopile is connected to an audio oscillator (as in N1-05) such that the frequency of the oscillator is proportional to the temperature observed: the hotter the object the higher the pitch. Use various sources: ice, boiling water, liquid nitrogen, the floor, people, etc. This is only qualitative; the system is not calibrated.
    N1, I2, PS1

  • I2-07: THERMOPILE WITH DVM

    I2-07
    Observe infrared radiation.
    The output from a commercial thermopile is connected to a digital voltmeter where the voltage is proportional to the temperature observed: the hotter the object the higher the voltage. Use various sources: ice, boiling water, liquid nitrogen, the floor, people, etc. This is only qualitative; the system is not calibrated.
    N1, ME2, I2, PW1

  • I2-21 THERMAL CONDUCTIVITY IN METALS

    I2-21
    Demonstrates thermal conductivity in various metals
    Heat from a gas burner at the center is conducted along rods of copper, aluminum, and brass. Wax blocks at the ends of the rods melt and drop off the rods due to the conduction of heat, in the following order: copper (3.98 Watts/cm deg C), aluminum (2.37 Watts/cm deg C), and brass (1.23 Watts/cm deg C).
    I2, I0

  • I2-22 THERMODYNAMICS BY TOUCH

    I2-22
    Demonstrates that touching a material tells something about its conductivity, not necessarily its temperature
    Various materials, all at room temperature, are arranged on a cart, and students are invited to touch them. The materials in order of increasing conductivity, are: styrofoam, wood, plastic, slate, steel, aluminum, and copper.
    I2

  • I2-27: THERMAL EQUILIBRIUM BETWEEN ALUMINUM AND COPPER

    I2-27
    Show process of thermal equilibrium happening between touching aluminum and copper cylinders.
    Pieces of copper and aluminum are held together by a large C-clamp. Small holes are drilled into the pieces to a allow a digital thermometer probe to be inserted to measure the temperature of each block, showing that the blocks are initially the same temperature, at equilibrium. Remove the thermometer probes and put a flame under one block to create a temperature difference. Remove the flame, reinsert the probes, and watch as the blocks come to thermal equilibrium.
    I2, I0, tools

  • I3-12: WATER BAROMETER - CAN CRUSHER

    I3-12
    Illustrate a result of atmospheric pressure.
    A rectangular can, connected to a long rubber hose, is filled with water from a large reservoir. The can is then raised about 15 feet, keeping the end of the hose in the water reservoir. The pressure differential between the inside and the outside of the can crushes the can as the water runs out in about 30 seconds. NOTE: Requires a high ceiling!

    i3-12a

  • I3-19: LIFTING USING ATMOSPHERIC PRESSURE

    I3-19
    Dramatically demonstrate an effect of air pressure.
    A rubber cup with a molded handle is held in contact with some horizontal object like a wooden box (in photograph above) or a cart top. Pulling upward on the handle allows you to lift the object, due to the ability of atmospheric air pressure to hold the rubber sheet in contact with the surface.
    I3

    i3-19ai3 19

  • I3-52: CONSTANT VOLUME GAS THERMOMETER - ABSOLUTE ZERO

    I3-52
    Determine the value of absolute zero.

    With a constant volume of air in the chamber, measure the pressure P(B) at the boiling point and the pressure P(F) at the freezing point of water. If the pressure P is read at some arbitrary temperature T, then that temperature in degrees celsius is:

    T=100 [P-P(F)] / [P(B)-P(F)]

    For an ideal gas, the pressure should go to zero at the temperature of absolute zero. Setting P=0, the value of absolute zero in degrees celcius can be calculated.

    Another way to do this is to plot a graph of pressure as a function of temperature. Draw the best line through the three points determined at boiling, freezing, and room temperature, and extend it so that it intersects the pressure axis, which is T=0 in celsius degrees.

    Above are photographs of the pressure gauge at each of the three points described.
    I3, I0

    i3-52ai3-52bi3-52c

  • I4-19: CONDENSATION OF STEAM - SODA CAN COLLAPSE

    I4-19
    Surprising demonstration using condensation of steam.
    A soda can with a small amount of water in the bottom is heated until the water boils, filling the can with steam. Very quickly the can is removed from the heater and inserted upside down into a container of cold water. The steam condenses so quickly that the can collapses, as seen in the photograph. This is quite a dramatic demonstration, and gets a good reaction from students.
    I4, I0, SU15

  • I5-32: STIRLING ENGINE

    I5-32
    Demonstrates a Stirling engine
    The Stirling engine is a closed-cycle regenerating heat engine using an external heat source. Air expands when heated, driving the piston, which drives the flywheel and forces cool air into the chamber for reheating. Heating the heat sink on the engine starts the flywheel rotating.

    Safety note: Please make very certain that fuel tank is fully closed when finished.
    I5

  • I6-33: MOLECULAR MOTION DEMO - GAS PRESSURE

    I6-33
    Model gas pressure.
    A set of about 20 steel balls models the air. A bar is positioned in the center of the device so that it will be continuously struck by the moving balls. The balls are set into motion by vibration of the walls with the device tilted. Collisions of the balls with the bar push the bar upward to model the force of a gas on a surface.
    I6, PW1

    i6-33a

  • I6-52: ENTROPY - FOUR BALLS IN GAS DIFFUSION MODEL

    I6-52
    Demonstrate that an ordered state is statistically possible.

    Place two balls of each of two different colors in the diffusion apparatus. To start, either place all four one the same side of the apparatus; or place two of one color on one side of the apparatus, and two balls of another color on the other side. Start the machine going with the hole between sides open.
    Engagement Suggestions
    • Encourage students to notice that although statistically it is less probable, the arrangement of both orange balls on one side and both green balls on the other side will happen occasionally.
    • Ask: Is this as likely to happen using three balls of each color? With four?
    Background
    This is essentially showing the exception to the general principle of demonstration I6-21. With a small enough number of balls in the model, it is statistically possible to “reverse entropy” to a limited extent – that is, occasionally, the balls will randomly organize themselves so that they are once again sorted by color.
    FS1

  • 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