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PHYS105

  • K5-14: ELECTRIC CELL

    K5-14
    Demonstrate how an electric cell is formed.
    A container is filled with a dilute solution of HCl or diluted vinegar, and and a pair of electrodes is inserted into the electrolyte solution. The voltage is measured using the lecture meter or digital interface. The standard electrode pair is copper and zinc.
    K5, ME2

  • K5-23: ROTATING TWO-COLOR LED

    K5-23
    Demonstrate that what comes out of a 110 VAC plug is in fact alternating current.
    The bi-color LED is wired across the 110 VAC line. When current flows one direction the red side glows, and when current flows the other direction the green side glows, so if it is viewed from a distance the color appears yellow. When the device is swung in a circle the alternating colors become easily visible, indicating that the current in the line is alternating direction. This new and improved version of the device was created by Prof. Steven Rolston.

    Try showing the class the light while it is stationary, then explain how it works and have them predict what it will look like in motion.

  • K5-31 OHM'S LAW

    K5-31
    Demonstrates relationship between current, voltage, and resistance

    This simple circuit consists of a variable voltage power supply and a socket that can hold one of three modular resistor units, with a ammeter measuring the current through the resistor and a voltmeter measuring the voltage across the resistor. The whole circuit is mounted on a transparent plate that can be placed on an overhead transparency projector to show the wiring and the meters.

    The voltage can be varied to show how the voltage and current change together in a linear relationship to the resistance. Both two 1,000 Ohm resistors and one 2,000 Ohm resistor modules are available; the two 1,000 Ohm modules can be placed in parallel if desired.

    It can be valuable to ask students to make predictions about how the results will change when you change the resistance, then afterwards have them discuss their predictions and compare them to the results.
    K5

  • K5-33 CONDUCTIVITY OF SALT SOLUTION

    K5-33
    Shows that pure water is not conducting, but a solution of an electrolyte is conducting
    A 110 VAC lead is connected to a series arrangement of a light bulb and two parallel plates. Shorting the plates will light the bulb. Inserting the plates into distilled water does not light the bulb. Inserting the plates into tap water lights the bulb dimly, and inserting the plates into salt water lights the bulb fully. An electrolyte solution allows passage of electric current.
    K5

  • K6-03 SERIES AND PARALLEL LIGHTS - BATTERY AND CLIP-ON WIRES

    K6-03
    Shows voltages and currents in series & parallel circuits
    Series and parallel combinations of light bulbs can be connected to the 7.5 volt battery source. Meters indicating current and voltage can be inserted in the circuit as required.

    Note that due to the aging of our large display galvanometers, this is better performed now with digital multimeters. A camera can be used to show them on the lecture hall screen if desired.
    K6, ME2

  • K6-22: ENERGY CONVERSION - IMMERSION HEATER

    K6-22
    Demonstrate quantitatively the conversion of electrical energy into heat.
    This 300-watt immersion heater is used to heat approximately 300 ml of water in a borosilicate beaker. Measure the initial water temperature with a digital thermometer, allow it to heat for a fixed time, then measure the final temperature. Compare the temperature change calculated for the energy conversion (as per Q=mcT where ! is the energy transferredm m is the mass of water, c is the specific heat, and T is the change in temperature) to that measured, and invite students to talk about the meaning of the difference (heat loss through the sides of the beaker, etc.).

    Note that the heater will (obviously) get hot! Do not allow it to burn your hand or the power cord.
    K6, I0

  • L3-16 FOCUSING OF HEAT WAVES BY MIRRORS

    L3-16
    Demonstrates that concave mirrors can focus heat waves
    Two parabolic concave mirrors are used to focus heat from a nichrome heater and light a match.
    L3, PW1

  • N1-05 SPECTRA - VISIBLE AND INVISIBLE

    N1-05
    Demonstrates continuous spectrum
    The carbon arc lamp is used to provide a continuous white light spectrum. Light from the arc lamp is focused by a condenser lens with iris and a 20 cm focal length cylindrical lens onto a slit. A 20 cm focal length convex lens then images the slit onto the screen through an equilateral prism. A fluorescent screen (with fluorescein) is used to show that there is ultraviolet radiation, including a strong UV line, in the carbon arc spectrum. A thermopile is used to sense infrared radiation, where the heat measured by the thermopile causes an audio oscillator to rise in pitch, so a hotter source produces a higher tone. (see I2-06 for more on this apparatus) Aiming the thermopile from the spectrum back toward the prism, it is observed that the hottest part of the spectrum is just off the red color, in the infrared.
    N1, OM1, LS1

  • N1-07: VARIATION OF SPECTRUM WITH LAMP INTENSITY

    N1-07
    Demonstrate continuous spectrum as the brightness of the source changes

    A bright white light source is directed through a series of lenses and a prism to provide a continuous white light spectrum. The intensity of the source bulb is adjusted using a variable transformer on the input to the light source.
    Engagement Suggestion
    • Encourage students to predict how changing the input power will change the spectrum. Will the spectrum grow uniformly brighter and dimmer, or will there be a change in what colors we see in what proportions?
    Background
    As the light intensity is decreased, the spectrum becomes less intense but also shifts significantly toward the red. Increasing the source intensity, and thus the blackbody temperature, shifts the spectrum to the blue as the intensity increases.
    OM1, LS1, PS1, FS0

  • O2-11 PULFRICH PENDULUM

    O2-11
    Demonstrates visual latency and the Pulfrich phenomenon
    Stand back 8-10 feet or more from the pendulum and swing the pendulum perpendicular to your line of sight. Watch the bob with both eyes and hold a dark filter over one eye to see the pendulum appear to move in an elliptical path. Hold the filter over the other eye to make the direction of rotation reverse. This effect is due to a delay in synapses along the optical nervous system between the retina and the brain of dimmer light signals relative to bright signals. Any dark filter or polaroid can be used; most commonly we use either the red or the blue filter from a pair of red/blue stereoscopic goggles. In darker rooms it may help to illuminate the pendulum bob with a goose neck lamp.

  • O4-31: TRAPEZOIDAL WINDOW

    O4-31
    Classic depth illusion.

    The trapezoidal window is rotated at about one revolution per two seconds by an electric motor in the box. When the taller side rotates away from us, it appears to reverse direction and rotate toward us.

    Everyone knows that any object appears to get smaller as it moves away and bigger as it moves toward you. Mind over matter!

  • O4-33: IMPOSSIBLE TRIANGLE

    O4-33
    Classic impossible triangle illusion with a twist.

    The classic impossible triangle is constructed from three orthogonal aluminum bars. The front bar has a cutout which is aligned with the rear bar so that the triangle appears closed when viewed from a particular point (or along a short line), forming an impossible figure.

    This gizmo bothers people more when it is set up with a pendulum apparently swinging through the "solid" metal of the triangle. The photograph shows the triangle with the pendulum at its equilibrium position along with the view of the triangle from an appropriately positioned camera.

    Photographs of actual 3D realizations of a number of Escher art works will be found at the "Escher for Real" web site http://gershonelber.org/EscherForReal/.

    Note: Due to complexities of setup, please give at least three working days notice when ordering this demonstration.

    o4-33o4-33BlockImpossibleTriangle

  • P2-06 PHOTOELECTRIC TRUCK

    P2-06
    Demonstrates solar cells
    Shine a 100 watt goose neck lamp onto the photocell on top of the truck to make it start; remove the lamp to stop the truck.
    P2, LS2

  • P4-06 RADIOACTIVE CONSUMER PRODUCTS

    P4-06
    Shows some consumer products and naturally occuring materials that are weakly radioactive
    A number of materials that are naturally occuring or consumer products can be investigated. Shown in the photo above (CCW from radiation detector at the lower right) are a Fiestaware plate, KCl salt substitute, and a commercial educational set of radioactive rocks. The Fiestaware contains a uranium gamma-ray source in its orange paint, and both the rocks and the welding rods are also gamma-ray sources. To observe radioactivity for the gamma sources it is only necessary to position the counter reasonably close to the sources. K40 is a source of 1.33 MeV betas with a half-life of about 1.3 billion years. Because of the more limited range of the betas, it is necessary to pour some of the salt substitute product into an open container and hold the window of the detector in contact with the product.
    SU19