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PHYS272

  • 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

  • J5-04: 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

  • J5-16 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

  • J5-20 OERSTED EXPERIMENT- LARGE COIL AND COMPASS

    J5-20
    Demonstrates that magnetic fields are generated around current-carrying wires
    The compass is positioned within the coil. When current is run through the coil the compass lines up along the axis of the coil in the direction of the magnetic field.
    J5, PS1

  • J5-34: DECLINATION AND INCLINATION NEEDLE

    J5-34
    Determine the declination and the inclination of the earth's magnetic field.
    Both magnetic declination and inclination, or dip, can be measured with good precision using this well-made instrument. The strongly magnetized needle is 10 cm long and mounted on sapphire bearings at the center of an 11-cm circular ring graduated to single degrees to indicate inclination. This ring is mounted on a horizontal diameter and is free to turn on a tapered bearing in the center of a tripod base, a 6-cm disk on the base being graduated to 5-degree divisions to indicate declination. The instrument is equipped with leveling screws and a spirit level for making the pillar accurately vertical. The over-all height is 28 cm. (from Sargent Welch catalog)

  • J5-36: MAGNETIC SPINNER

    J5-36
    Demonstrate magnetic levitation.
    Axle with two magnets mounted on it levitates above a magnetic base as it spins.

  • J5-51: GAUSSMETER

    J5-51
    Demonstrate use of a gaussmeter
    This is a Hall probe gaussmeter of research quality. It can measure fields from a fraction of a gauss to over 10 kilogauss (1 Tesla). Radial (the flat one) and axial (the cylindrical one) probes are included. Ask for magnets (Demonstration J5-04: MAGNETS) and measure their fields with a gaussmeter.
    J5, K1

  • J6-02: ELECTROMAGNET WITH JUNK

    J6-02
    Demonstrate an electromagnet.
    Close switch to pick up junk with coil. Release switch to let junk fall. Some light items may cling to the magnet after the switch is released due to residual magnetism of the core.
    J6, PS1

  • J6-03: ELECTROMAGNET WITH JUNK - WITHOUT CORE

    J6-03
    Demonstrate electromagnetism.
    This shows the functioning of J6-02 without the iron core. The absence of a core makes the field weaker, but the physics a bit simpler.
    J6, PS1

  • J6-04: LOW-POWER HIGH-FORCE ELECTROMAGNET

    J6-04
    Show that a small amount of energy can produce large magnetic forces
    A magnet and keeper are held together by energizing the magnet with a flashlight battery. It usually takes more than one person pulling on each side to separate the magnet and keeper.
    J6

  • J7-01: LODESTONE

    J7-01
    Demonstrate the natural magnetism of lodestone.
    Bring a compass up close to the lodestone to demonstrate that it is magnetic.

  • J7-11 PARAMAGNETISM AND DIAMAGNETISM

    J7-11
    Demonstrates paramagnetic and diamagnetic materials
    A sample of copper sulfate, a paramagnetic material, is slightly attracted to a magnet. A sample of bismuth, a diamagnetic material, is slightly repelled by a magnet. Samples of copper sulfate and bismuth are balanced on a light dowel rod hanging by a strip of plastic audio recording tape. The 2-kilogauss horseshoe magnet is used to push and/or pull the samples around, illustrating the small paramagnetic and diamagnetic forces.
    J7

  • K1-03 FORCE ON CURRENT IN MAGNETIC FIELD

    K1-03
    Demonstrates force on a current-carrying wire in a magnetic field

    A wire (reinforced by a plastic tube for safety) passes between the pole tips of a strong magnet. When the key is pressed so that current flows in the wire, the wire jumps out from between the pole tips.
    Engagement Suggestion
    • Once students have seen what happens, encourage them to predict the results of reversing the direction of the flow of current. Then swap the leads and show what happens. Have them discuss the results.
    • What if you flip the magnet itself over? Again, have them predict what will happen, then try the experiment and discuss.
    Background

    This illustrates the Lorentz force, or Laplace force, as predicted by Maxwell’s equations. A current flowing through a magnetic field experiences a force determined by the cross product of the current vector and the magnetic field.


    See demonstration K1-04 in this section for a more portable version of this experiment.

    K1

  • K1-12 CATHODE-RAY TUBE - DEFLECTION BY MAGNET

    K1-12
    Demonstrates the force on an electron beam by a magnetic field
    The cathode ray discharge tube produces an electron beam moving from left to right, which can be seen on the fluorescent screen inside the tube. Holding a bar magnet close to the tube, parallel to the tabletop so that it produces a horizontal magnetic field inside the tube, causes the electron beam to deflect up or down. If the directions of the magnet's poles are reversed, the direction of the deflection should also reverse, illustrating the vector nature of the force.

    If desired, a video camera may be requested to display this demonstration on the projection screen in the large lecture halls.
    K1

  • K1-21 TORQUE ON CURRENT LOOP IN MAGNETIC FIELD

    K1-21
    Demonstrates the torque on a current loop in a magnetic field
    A few-turn coil is positioned in the magnetic field of a small horseshoe magnet, as shown in the photograph. Pushing the switch connects the battery to the coil, passing electrical current through the coil and creating the torque, which is visible as a small rotation of the coil about its axis. Reversing the coil leads reverses the direction of the torque.

    A video camera can be made available upon request for displaying this demonstration in large lecture halls.
    K1

  • K1-22 TORQUE ON 500-TURN COIL IN MAGNETIC FIELD

    K1-22
    Demonstrates the torque on a current loop in a magnetic field
    A large coil sits between the poles of strong magnets, with the plane of the coil parallel to the magnetic field lines. A large current pulse can be applied to the coil by charging and then discharging a capacitor. When the current pulse is applied to the coil, a torque is exerted on the coil by the magnetic field which rotates the coil so that the magnetic field is perpendicular to the plane of the coil. This effect can be quite dramatic; be sure to keep fingers clear of the magnets.

    Charge capacitor to no more than 25V.
    K1

  • K1-31: MAGNETOHYDRODYNAMIC GENERATOR

    K1-31
    Illustrate magnetohydrodynamic forces.
    A shallow bowl of copper sulfate solution is placed in the (downward) magnetic field of a medium-strength horseshoe magnet. An electron current is created between the negative electrode band around the circumference of the bowl and the positive electrode at the center of the bowl. The resulting vxB force on the electrons creates counterclockwise rotation of the copper sulfate solution. Small pieces of paper are dropped onto the surface of the rotating liquid as an indicator.
    K1, PS1

  • K2-01 EARTH INDUCTOR

    K2-01
    Induces an emf by moving a coil through Earth's magnetic field
    A large wire coil is connected to a projection galvanometer. Motion of the coil through the magnetic field of the earth induces an emf which is indicated on the meter. Alignment of the coil relative to the earth's magnetic field lines can be found which produces a maximum deflection of the coil, or almost no deflection. Optionally, a bar magnet (available upon request) can be thrust in and out of the coil to induce a larger voltage, illustrating the relatively low strength of the Earth's field.
    K2

  • K2-02 INDUCTION IN A SINGLE WIRE

    K2-02
    Demonstrates magnetic induction
    A single wire is connected to a projection galvenometer. Passing the wire quickly between the pole tips of a strong permanent magnet induces electric current, which is seen on the meter.
    K2, K1