Follow

Inductance

  • J2-33: TESLA COIL - PORTABLE

    J2-33
    Easy-to-use high-voltage device for use in various demonstrations or just to draw a nice spark.
    This is an easy-to-operate 110V/60Hz device that reliably produces a nice spark. It can be used to demonstrate discharge to grounded objects. Please handle carefully.
    J2b

  • 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.

  • J6-33: ELECTROMAGNETIC GUN

    J6-33
    Demonstrate the force on a solenoid core, and to contrast forces on magnetic and non-magnetic cores.
    This demonstration uses the coil from demonstration K2-22, but in an unusual configuration:

    (1) Insert iron core, displace it as far as possible toward the base, and apply current until the core reaches the center of the coil. The core will eject a few meters. (2) Insert copper core (hollow) about one inch forward of the center of the coil. Apply current to slowly eject the core. (3) Insert both cores about an inch forward of the center of the coil. Predict the results. Dramatic. Stand clear!!

    K2, PS1

  • 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

  • K2-11: SELF-INDUCTION

    K2-11
    Demonstrate self-induction
    A 1.5V battery and switch are connected to a neon bulb in parallel with a large coil. When the switch is closed, connecting the battery to start current flowing in the large coil, there is no visible effect on the bulb. When the switch is turned off, however, the collapsing field creates a back EMF sufficient to light the neon bulb (about 90 volts). Note that the switch and coil have exposed terminals; while the current here is very low and generally harmless, it is wise to try to avoid contact with the exposed terminals.
    K2

  • K2-12: SELF-INDUCTION - DEMOUNTABLE TRANSFORMER

    K2-12
    Demonstrate back-EMF in an inductor.
    A 1000-turn transformer coil and a neon bulb connected in parallel are connected in series with a 7.5 volt battery and a key switch, as shown in the circuit below. When the switch is closed current flows in the inductor. When the key is released the field of the inductor collapses, inducing an EMF sufficient to light the neon bulb.
    K2, K3, PS1

  • K2-22 INDUCTION COIL WITH LIGHT BULB

    K2-22
    Demonstrates megnetic induction with 110 VAC
    Closing the switch puts 110 VAC on the primary coil, which is coupled to the secondary coil (on top) by a ferromagnetic core. The induced current in the secondary coil lights the 110 VAC light bulb.

  • K2-24: MUTUAL INDUCTION

    K2-24
    Demonstrate mutual induction.
    Two pairs of concentric coils are coupled by an iron core. Connect 9-volt battery to start and stop current in any one of the coils. The current induced in any of the other coils can be seen using the galvanometer. Connecting battery to coil with meter will damage the meter.

  • K2-25: MUTUAL INDUCTION - DEMOUNTABLE TRANSFORMER

    K2-25
    Demonstrate mutual induction and to show the effect of various core materials.
    Two matching 500-turn coils from the demountable transformer set are positioned adjacent to each other. Switching the current in the primary on and off induces short spikes of current in the secondary. Rods of various core materials are available; experiment with the class to determine their effect on the induced current. While holding down the key so that current is flowing in the primary coil, insert and remove various cores. Have the class make predictions as to the effect of different materials.
    K3, PS1, ME2

  • K2-26: MUTUAL INDUCTANCE STANDARD

    K2-26
    Demonstrate the standard for mutual inductance.
    A tall coil serves as the primary of a simple transformer. A smaller coil wraps around its center as a secondary. Switching the current in the primary on or off induces a calibrated voltage in the secondary. This can be displayed on a projection meter.

    If desired, the roles can be reversed to show the effects; also, a center tap is available.,/p>

    K1, K2, PW1

  • K2-27: MUTUAL INDUCTION - M12 eq M21 MEASUREMENT

    K2-27
    Demonstrate that the mutual inductance between two coils is independent of which one is the primary.
    Two coils with different shape and number of turns are used as the primary and the secondary in a transformer. (Case 1) The oscillator produces an AC current for the primary coil, which is displayed on the upper trace of the oscilloscope. The voltage across the secondary is displayed on the lower trace. (Case 2) The leads are then swapped between the two coils, without changing their positions, and the primary current is adjusted so that it is the same as that for the first case. The secondary voltage will also be the same as the first case. The voltage of the secondary of a transformer is equal to the current in the primary times the mutual inductance. Because this system is symmetric the mutual inductance going either way must be the same, being only a function of the geometry.
    K2, ME2, ME3

  • K2-28: DEMOUNTABLE TRANSFORMER - 10 KV ARC

    K2-28
    Demonstrate that a large voltage increase is attainable using a transformer.
    The 250-turn primary coil is plugged into 110 VAC. The turn ratio of nearly 100 produces a large secondary voltage which arcs across electrodes placed on the output of the 23,000-turn secondary coil.
    K3, PS1

  • K4-08: MAGNETOELECTRIC GENERATOR WITH INDUCTOR

    K4-08
    Demonstrate how a magnetoelectric generator stores energy in an inductor and how that energy is returned to the generator.
    A "Genecon" hand-cranked motor-generator is used to store energy in the large inductor from demonstration K2-11. While the handle is being cranked, it is stopped and immediately released.

    A question for the students: What will the handle do? (a) continue to move in the same direction, (b) reverse, and move in the opposite direction, or (c) immediately stop and not move at all.

    Note: When preparing to use this demonstration, make certain that the attached knife switch is open, or it will short out the generator and damage it (as well as failing to demonstrate induction).

    K4, K2

  • K7-01: RL CIRCUIT - 50 MICROSECOND TIME CONSTANT

    K7-01
    Illustrate RL time constant.
    A resistance box and an air-core coil (from K2-27) are used in an RL circuit. The inductance of the air-core coil can be calculated (if desired) and the time constant L/R calculated from the inductance and the resistance of the box. This can be compared with the experimental result. The signal source, a square wave of about 2000 Hertz, is displayed on the upper trace, and the current in the RL circuit on the lower trace. See circuit above.
    K2, K7, ME2, ME3

  • K7-02 RL CIRCUIT - L/R TIME CONSTANT

    K7-02
    Shows L/R time constant for a slow circuit
    A nine-volt battery is used to energize the LR circuit while the current through the LR system is observed on an oscilloscope. The system is then shorted and allowed to de-energize. This setup uses an approximately 6 kilohenry coil and about 12 kilohms series resistance to produce a time constant of about 1/2 second.

  • K7-03 INDUCTOR DELAYING A LAMP

    K7-03
    Demonstrates the timing of current in a switched inductor circuit
    An inductor and light bulb are connected across a battery with a switch. In parallel with this inductor and light bulb is a second identical light bulb. The separate light bulb will light immediately, but the light bulb in series with the inductor will be delayed in lighting until the current reaches a high enough level. The delay time is related to the L/R time constant of that leg of the circuit.
    K7, PS1

  • K7-04: RL CIRCUIT - FIELD COLLAPSE WITH FLUORESCENT BULB

    K7-04
    Demonstrate the magnitude of induced voltage
    A 9-volt battery is connected across a large inductor; pushing the red button disconnects the inductor from the battery and immediately connects it across a fluorescent light tube. Collapse of the magnetic field in the inductor induces a voltage large enough to cause the fluorescent bulb to flash - well over 100 volts, or over ten times the voltage of the battery.
    K7

  • K7-05: SERIES MOTOR AND LIGHT BULB CONUNDRUM

    K7-05
    Generate thought about how a motor works.
    A 1.5 volt motor and 1.5 volt light bulb are wired in series such that a 1.5 volt battery can be connected across either of them individually, or across both in series. The first mpeg video linked below shows what happens when each is connected to the battery individually.
    Ask the students what will happen when both are connected in series: Will (a) only the light bulb operate, (b) only the motor operate, (c) both operate, or (d) neither operate?
    Again, only the motor spins, as seen in he second mpeg video below.

  • K7-30: RLC CIRCUIT - RINGING

    K7-30
    Demonstrate ringing in a simple RLC circuit.
    A capacitor is charged and immediately connected to a series RLC circuit. The oscillation of the voltage across the capacitor of the RLC circuit is recorded using an oscilloscope. Pressing the red switch charges the capacitor; releasing the switch connects the capacitor back to the series RLC circuit, initiating the ringing effect. The circuit diagram is on the apparatus, as seen in the picture above. The oscilloscope is not shown in the picture.

  • K7-31: RLC CIRCUIT - OVER/UNDER/CRITICAL DAMPING

    K7-31
    Demonstrate over/under/critical damping in a series RLC circuit.
    The capacitor in an RLC series circuit is charged and then quickly allowed to discharge through the circuit. The series resistor is a potentiometer that can be adjusted to produce underdamping, critical damping, or overdamping, shown left-to-right in that order on the circuit assembly photograph above. The voltage across the capacitor is can be displayed on an oscilloscope (not shown).