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PHYS260

  • I5-02: TRANSFORMATION OF MECHANICAL ENERGY INTO HEAT

    I5-02
    Demonstrate transformation of mechanical energy into heat.
    Use an electric drill to spin a wooden dowel rod in a hole on a large wooden beam. Shortly the contact point begins to smoke, indicating generation of heat due to friction.
    I3,I5

    i5-02a

  • I5-11 ADIABATIC PROCESS - AIR PISTON WITH THERMISTOR

    I5-11
    Demonstrates adiabatic compression and expansion of air
    A thermister is enclosed in a small cylinder of air, the volume of which can be rapidly changed by moving a piston up and down. Pushing the piston down compresses the air, the air heats and the temperature increases, producing an increase in the resistance of the thermistor. Pulling the piston up expands the air adiabatically, the air cools and the temperature decreases, producing a decrease in the resistance of the thermistor. The thermistor is identical to those used in the thermometer probes of the old commercial digital thermometer.
    I5, I0

  • I5-13: ADIABATIC EXPANSION OF AIR - GRAPH OF TEMP

    I5-13
    Demonstrate adiabatic expansion of air by plotting the temperature.
    A tightly corked bottle containing air with a small amount of water is pressurized using a bicycle tire pump. When the cork pops the air expands adiabatically, cooling sufficiently to form fog in the bottle. The computer plots a graph of the air temperature in the jar using a thermistor probe, as seen in detail below. As air is pumped into the jar the temperature slowly rises; when the cork blows the temperature suddenly falls to below its initial level. The graph can be displayed on video projectors in the lecture hall.

    i5-13a

  • I5-22 FIRE SYRINGE

    I5-22
    Demonstrates heating air by compression

    This demonstration consists of a transparent cylinder with a flared base, and a plunger that can be pushed into it. A small (very small) piece of cotton is pushed into the bottom of the tube using the wire provided, and the plunger is sealed into the tube. The plunger is pushed down sharply, compressing and thereby heating the air within. The temperature rises high enough to ignite the cotton with a flash, which can be readily seen through the plastic tube.
    Engagement Suggestion
    • Consider inviting a volunteer from the audience to try the demonstration. This will require careful supervision, but is safe. Just ensure that the syringe isn't knocked off the table by an overenthusiastic student!
    • This demonstration works best with a very small amount of cotton to ignite, no more than a few millimeters at most. Consider showing the device with different amounts of cotton, and how the results change. Encourage students to discuss reasons for this.
    Background
    This demonstration illustrates that an essentially fixed mass of air will increase in temperature when its volume is reduced, i.e. it is heated when compressed. The fire syringe is a simple piston, and can be used to introduce a discussion of the use of pistons in engines.

    Consider using this demonstration in conjunction with both other thermodynamics demonstrations from section I5, and relating it back to general gas behaviour with demonstrations from section I3.
    I5

  • I5-31 STEAM ENGINE - STATIONARY

    I5-31
    Working model of a steam engine
    The engine can be attached to a weight hanging by a string over an axle which is connected to the engine through a series of gears.
    I5

  • 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

  • I5-33 STEAM ROLLER

    I5-33
    Toy steam roller with real steam engine
    Fire up the engine, put it into gear, and let it roll. Try the whistle.
    I5

  • I5-51: SPECIFIC HEAT - ALUMINUM AND COPPER

    I5-51
    Illustrate calorimitry and to determine experimentally the specific heats of aluminum and of copper.
    Boil the aluminum and copper blocks in a pan of water and place the metal blocks at 100 degrees C into equal amounts of water at room temperature in two styrofoam containers. Stir the water in the containers with the digital thermometer probe, measuring the temperature when equilibrium is reached. From these measurements the specific heats can be determined.

    Multiply the specific heat by the molar mass to find the molar specific heat. The values for both materials are nearly the same and equal to 3R=6(1/2)kT.
    I5, I0, ME1

  • I6-01 GAS PRESSURE - MODEL

    I6-01
    Illustrates the molecular nature of gas pressure
    A vibrator motor is activated causing chaotic motion of a group of ball bearings in a clear plastic container. The upward motion of the ball bearings pushes a black plastic plate upward, indicating the upward force of "air pressure" on the plate. Increasing the speed of the motor by turning up the variac increases the average speed of the balls and pushes the plate up further, modeling a greater pressure.
    I6, PW1

  • I6-03 EQUIPARTITION OF ENERGY

    I6-03
    Demonstrates equipartition of energy
    Into the glass bowl are placed balls of the same size but three different masses: ping pong balls, cork balls, and superballs. Shaking the bowl gives all of the balls approximately the same kinetic energy. Because the light balls have greater velocities for the same average kinetic energy, as you shake the bowl more and more fervently first the ping pong balls, then the cork balls, and finally the superballs jump out.
    I6

  • I6-23 DIFFUSION - FOOD COLOR IN WATER

    I6-23
    Demonstrates diffusion
    A drop of food coloring is placed gently into a beaker of water. In a few minutes the food coloring will diffuse through the entire beaker of water.
    F2, glassware

  • I6-26: DIFFUSION - PERFUME

    I6-26
    Illustrate diffusion.
    Spray the perfume into the air and the students soon notice the fragrance of the perfume. Point out that the perfume fragrance spreads through the room due to diffusion. Be sure to point out that there may be other reasons why the fragrance spreads, such as air currents.

  • I6-32: MOLECULAR MOTION DEMO - RANDOM MOTION IN GASES

    I6-32
    Model random molecular motion.
    A set of small balls of the same mass models the air. Random motion of any ball can be observed.

    i6-32a

  • 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

  • I6-34: MOLECULAR MOTION DEMO - TEMPERATURE OF A GAS

    I6-34
    Model gas pressure.
    Two sets of small balls (larger green and smaller blue) are used to model the molecules in the air. The balls are set into motion by vibration of the walls. Increasing the vibration speed of the walls imparts more energy to the balls, simulating higher temperature.

    Using a single set of balls, the distribution of velocities can be observed. Using two sets of balls with different mass, the average velocity of the smaller balls is seen to be greater than that of the larger balls.
    I6, PW1

    i6-34a

  • I6-38: MOLECULAR MOTION DEMO - BOYLE'S LAW

    I6-38
    Model Boyle's law.
    A set of small balls of equal mass models the air. The balls are set into motion by vibration of the walls with the device level. A bar is positioned in the device to divide the volume into two parts, with all of the balls on one side. A rough observation of the rate at which balls hit the wall is then made. The bar is removed, keeping the motion the same. Note that fewer balls hit the same section of wall in the same time, indicating that when the volume increased the pressure decreased.

    i6-38bi6-38a

  • I6-39: MOLECULAR MOTION DEMO - CHARLES' LAW

    I6-39
    Model Charles' law.
    A set of about 20 small steel balls of equal mass models the air. The balls are set into motion by vibration of the walls with the device tilted. A moveable bar positioned in the device is pushed upward by collisions with the balls. As the vibration rate of the walls is raised, raising the temperature and thus increasing the average molecular speed, the bar is pushed further upward, representing increased volume at a constant pressure (the weight of the bar). Use of a 140 Volt Variac extends the temperature range upward to make the trend more clear.
    I6, PW1

    i6-39a

  • I6-40: MOLECULAR MOTION DEMO - SOLIDS

    I6-40
    Model the behavior of solids.
    A set of small balls of equal mass is placed in the vibrator in a curved glass dish with the concave side up. The gravitational force caused by the curvature of the dish causes them to form an array, corresponding to a crystal lattice. As the vibrator motion is increased, the molecules do not move about randomly, but rather vibrate about their original positions, representing vibratory motion of atoms in a crystal lattice.

    i6-40ai6-40b

  • I6-41: MOLECULAR MOTION DEMO - LIQUIDS

    I6-41
    Model the behavior of liquids.
    Using the arrangement of balls from the solid (Demonstation I6-40), the vibration speed is further increased. The balls remain in a small clump, with a few "boiling off" but most free to migrate within the tight clump, representing molecular motion within the liquid state. Use of a Variac operating at 140 VAC makes this effect more clear.

    i6-41ai6-41b

  • I6-51 ENTROPY - SORTING MARBLES

    I6-51
    Demonstrates that increasing entropy requires less energy than decreasing entropy
    Shaking the system with the larger holes on the top causes the marbles to separate by size (yellow, green, pink, and blue). Simply inverting allows them to fall under the influence of gravity to their lowest level and mix. It apparently takes more energy to unmix the marbles than to mix them.
    I6