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Magnetic Fields and Forces

  • C4-54: WEIGHTLESSNESS IN FREE FALL - MAGNET AND KEEPER

    C4-54
    Illustrate weightlessness in free fall.
    The keeper is placed on an aluminum shelf about two centimeters below the "C" magnet; the gravitational force on the keeper is sufficient to keep it from being attracted to the magnet. When the system is released and allowed to fall with the acceleration of gravity, the keeper becomes weightless and is attracted to the magnet

  • I1-41: THERMOELECTRIC MAGNET

    I1-41
    Demonstrate production and use of thermoelectric current.
    One junction of the thermocouple is kept at the temperature of ice, and the other heated by a burner, thus generating a large thermoelectric current. The current forms a single loop through the two sections of an electromagnet. The bottom section is a 5 kG mass, which can be supported by the magnetic field created by the thermoelectric current when the device is lifted by the hook on the top section after about 2 minutes of heating.

  • I7-21: SUPERCONDUCTOR - MAGNET LEVITATION

    I7-21
    Demonstrate levitation of a magnet above a high-temperature superconductor
    A one-inch diameter superconducting disc is set on a conducting base in a bath of liquid nitrogen. A cubic samarium cobalt magnet levitates above the superconductor. Note that to show the Meissner effect you must place the magnet on the disc before cooling it down. When the superconductor passes through its transition temperature the magnet rises up by itself and levitates. For large groups, a camera can be provided.
    I7, I0

  • I7-23: Magnetic Track and Superconductor

    I7-23
    To illustrate levitation of a superconductor and magnetic pinning
    A chilled superconducting puck is levitated above a magnetic track. Despite the curve and slope of the track, the puck will remain above the track as it moves.

    This is an illustration of the diamagnetic and magnetic pinning effects of a superconducting material. When setting up, be sure to chill the puck in the position you want it above the track for maximum efficiency.

    The University of Cambridge has made available a helpful video lecture on magnetic pinning: https://ascg.msm.cam.ac.uk/lectures/fundamentals/pinning.php.

  • 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

  • J5-02: MAGNETIC FIELD - EME SET - BAR MAGNET

    J5-02
    Visualize the magnetic field of a bar magnet.
    This is a commercial version of the magnetic field visualization using iron filings. Place the magnet beneath the plastic box on an overhead projector, sprinkle on filings and tap to get the filings to line up along the magnetic field lines.
    J5

  • J5-03: MAGNETIC FIELD OF A BAR MAGNET - 3D VERSION

    J5-03
    Three-dimensional field visualization of magnetic field of bar magnet.
    A cylindrical bar magnet is inserted into the center of a cube filled with a suspension of magnetic powder. When the device is shaked, mixing the magnetic powder uniformly through the liquid, and the magnet inserted, the powder lines up along field lines, allowing three-dimensional visualization of the field of a bar magnet.
    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

  • J5-07: MAGNETIZED WIRE FIELD LINE INDICATOR

    J5-07
    Demonstration of field lines using magnetized wires.
    A bar magnet is placed on top of the wire array, and the wires become magnetized and line up along the magnetic field lines.
    J5

    j5-07a

  • J5-08:

    J5-08
    To illustrate magnetic fields
    ...
    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

  • J5-12: MAGNETIC FIELD - EME SET - TWO-TURN HELIX

    J5-12
    Visualize the magnetic field around a two-turn helix.
    The magnetic field around a two-turn helix can be visualized by sprinkling iron filings in the area around where the helix passes through a plastic sheet which is positioned on an overhead projector. Alternatively, small compasses can be arranged within and around the helix.

  • 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

  • J5-17: HELMHOLTZ COILS AND HALL PROBE

    J5-17
    Investigate quantitatively the magnetic field of a pair of Helmholtz coils.
    Current is passed through a pair of Helmholtz coils and the magnetic field measured using an azimuthal Hall effect probe. The field of the Helmholtz coils can be seen to be very uniform over a large volume near the center of the coils. Have your students do the calculation showing that spacing the coils at a distance equal to their radius provides the greatest volume of nearly uniform field by producing zero gradient in the axial component of the magnetic field at the center of the coils.
    J5, OS9, PS1

  • J5-18: OERSTED EXPERIMENT

    J5-18
    Demonstrates that magnetic fields are generated around current-carrying wires
    A compass needle is mounted directly below a wire on a clear plastic sheet which is positioned on an overhead projector. When a current (provided by a battery and switch) flows in the wire the compass needle lines up perpendicular to the wire, showing that the current-carrying wire produces a magnetic field perpendicular to the wire. The action is viewed using an overhead projector. The two geometries are excited individually, as seen in the center (left coil) and right (right coil) photographs. However, notice that the compass near the wire that is not being excited is affected by current in the other coil.
    J5, PS1

    j5-18b j5-18a

  • J5-19: MAGNETIC FIELDS OF PARALLEL AND ANTIPARALLEL CURRENTS

    J5-19
    Show the magnetic fields of parallel and antiparallel current-carrying wires.
    Overhead projector projectuals have been constructed for parallel and antiparallel currents in wires. The difference between the magnetic fields in these two cases can easily be seen.

    j5-19a

  • 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