Magnetism

B-S1 : 2D Magnetic Field Lines

Unit

Magnetic Fields

Purpose

To show magnetic field lines in 2D

Equipment

  1. Assorted magnets
  2. 2D field visualizer

Suggestions

Experiment with different magnet shapes (ring magnets are particularly interesting)

Discussion

  1. Equipment
  2. Magnetic field lines of horseshoe magnet
  3. Magnetic field lines of ring magnet
  4. Magnetic field lines of cylindrical magnet

B-S2 : 3D Magnetic Field Lines

Unit

Magnetic Fields

Purpose

To illustrate magnetic field lines in 3D

Equipment

  1. 3D field line visualizer
  2. Magnet

Suggestions

  1. Try magnets with different sizes and shapes.
  2. Before use, shake the visualizer to evenly distribute the iron filings.

Discussion

3D magnetic field lines of the magnet

B-S3 : Biot-Savart Law

Unit

Magnetic Fields

Purpose

To demonstrate Biot-Savart Law

Equipment

  1. Biot-Savart law demonstrator (stand, compass needle)
  2. Power supply (with wires)

Suggestions

Before turning on the current, orient the base so the needle is parallel to the wire.

B-S4 : Ampere's Law

Unit

Magnetic Fields

Purpose

To illustrate the direction of magnetic field due to current in a wire. (Right-Hand Rule II)

Equipment

  1. Oersted Equipment Kit
  2. Laboratory DC Power Supply Model: GPS-1850
  3. Two banana head wires

Suggestions

  1. Experiment is to be done way from current-carrying wires.
  2. Rotate kit at different angles and observe the compass. Note the effect of Earth's magnetic field.

Discussion

  1. Equipment
  2. Compass's aligning with the Earth's magnetic field
  3. No current or voltage being used.
  4. Compass's aligning with the induced magnetic field.
  5. Current and voltage being used.

B-S5 : Large Ampere's Law

Unit

Magnetism

Purpose

To Demonstrate Ampere's Law

Equipment

  1. Wires
  2. Base 
  3. Power Supply

Discussion

  1. Equipment
  2. Wires pushed apart (anti parallel currents)
  3. Wires pulled together (parallel currents)

B-S6 : Helmholtz

Unit

Magnetic Fields

Purpose

Illustration of a magnetic field produced by a current

Equipment

  1. Helmholtz coils on base
  2. Compass
  3. Hall Effect Sensor
  4. Power supply (with wires)

Suggestions

Put the compass closest to the middle so it lines up straight with the magnetic field.

Discussion

  1. Compass aligning with magnetic field produced by coil
  2. Compass aligning with magnetic field produced by coil
  3. Hall effect sensor in the magnetic field produced by coil

B-S7 : B Field Coils

Unit

Magnetic Fields

Purpose

Illustrate magnetic field lines

Equipment

  1. Coil Plate
  2. Power Source (with wires)
  3. Iron Filings

Suggestions

Gently tap the plate to let the iron filings align with the magnetic field.

Discussion

  1. Equipment
  2. Iron filling not aligned (current off)
  3. Iron filling aligned (current on)

B-S8 : Semaphore Magnetic Force

Unit

Magnetic Force

Purpose

To demonstrate magnetic force on a current carrying wire

Equipment

  1. Large Magnet with attached semaphore (eagle)
  2. Power supply (with wires)

Suggestions

Switch the current direction to illustrate the direction of the magnetic force. The field of the magnet points up.

Discussion

  1. Equipment in starting position
  2. Semaphore after current is run from the red terminal to the black

B-S9 : Lorentz Force (I)

Unit

Magnetic Force on Moving Charges.

Purpose

Illustrate F = qv x B

Equipment

  1. Lorentz Force Projection Demo.
  2. NaOH solution
  3. DC Power Supply Model: GPS-1850

Suggestions

  1. Current on 1-3 A, no magnets; no motion
  2. Single pair of magnets with B "up"; vary the current, I=0.5-3 A. Reverse the current direction.
  3. Keep i=const. Add the second pair of magnets.

Discussion

1. Equipment
2 & 3. Current flowing radially out

B-S10 : Lorentz Force (II)

Unit

Electrodynamics

Purpose

To illustrate the effects of magnetic fields on moving electrons

Equipment

  1. Tesla Coil
  2. Discharges Tubes
  3. Connecting Wires
  4. Magnet

Suggestions

Use the magnet to deflect the electron beam and verify the right hand rule.

Discussion

1. Equipment
2-3. Electron beam with cross down
4-5. Electron beam with cross up

B-I1 : Electric Motor

Unit

Magnetism

Purpose

To demonstrate how an electric motor works

Equipment

Electric motor model

Suggestions

Experiment with different connections on the motor.

Discussion

  1. Equipment
  2. Electric motor in operation

B-I2 : Old Generator

Unit

Induction

Purpose

Illustrate how an electric generator works

Equipment

  1. Power supply
  2. Multimeter
  3. Banana Wires
  4. Generator

Suggestions

Set the multimeter for AC current for best results.

Discussion

  1. Equipment
  2. Generator in operation with intermittent contacts
  3. Generator in operation with continuous contacts
  4. Generator

B-I3 : Eddy Pendulum

Unit

Induction

Purpose

To demonstrate the effect of eddy currents

Equipment

  1. Pendulum base
  2. 3 pendulum bobs (solid, partially slit, fully slit)
  3. Variable gap magnet

Suggestions

  1. For best results, make sure the magnets are close together
  2. Can you determine the direction of the eddy currents?
  3. Poll the students on the effects of the slits.

Discussion

  1. Equipment
  2. The pendulum in action

B-I4 : Lenz's Law

Unit

Faraday's Law

Purpose

Illustrate Lenz's Law

Equipment

  1. Two aluminum tubes, 1 m each, with a coupler.
  2. Two masses: One "placebo" and one with magnet
  3. Round scale to measure force (0-10 N)

Suggestions

  1. First use the "placebo", then the magnet.
  2. Then hook up the scale and ask what the scale will read while the magnet falls.

Discussion

  1. Drop the "placebo" cartridge through one tube tf = √(2d/g) = √(0.2) = 0.44s 
  2. Drop the magnet cartridge; tf ~ 8s
  3. Repeat with 2m tube
  1. Equipment
  2. Timing magnet going down tube
  3. Weight of tube
  4. Waiting to drop magnet down tube to see weight change
  5. Weight of tube while magnet is going through

B-I5 : Rotational Lenz's Law

Unit

Induction

Purpose

To demonstrate Lenz law

Equipment

  1. Rotating loops on a base
  2. Magnet

Suggestions

Pass the magnet through the loops of the coil and observe the effect.

Discussion

B-I6 : Faraday's Law (I)

Unit

Induced Current

Purpose

Illustrate the induced emf in solenoids do to changing magnetic flux.

Equipment

  1. Faraday's-Electromagnetic Induction projectual
  2. Green and red bar magnets
  3. 6 volt Battery (for demonstrating the built-in ampmeter) and a resistor.
  4. Banana to alligator wire and alligator to alligator wire

Suggestions

  1. Hold the magnet in one of the solenoids (no effect).
  2. Move back and forth. Reverse direction. Vary the speed of the cut.
  3. Show the effects of increasing the number of turns by making similar cuts in all three solenoids.

Discussion

  1. Equipment
  2. Small positive current
  3. Small negative current
  4. Medium positive current
  5. Medium negative current
  6. Large positive current
  7. Large negative current
  8. Equipment for using battery
  9. Negative current
  10. Positive current

B-I7 : Faraday's Law (II)

Unit

Induced Current

Purpose

Illustrate the induced emf in solenoids do to changing magnetic flux.

Equipment

  1. Rotating Platform
  2. Variable Gap Magnet
  3. Table Clamp
  4. Threaded Rod (1/2-13)
  5. ME-8955 Motor Drive (optional)
  6. Laboratory DC Power Supply Model: GPS-1850 (Optional)

Suggestions

  1. Rotate the platform first in one direction and then in the other, noting the effect on the sequence of LED color change.
  2. Vary the angular velocity and note the effect on the length of the light track.
  3. Vary the length of the gap between the magnets and note the effect on LED intensity.
  4. Put the pole pieces, which spread the magnetic field evenly, on the neodymium magnets and note the effect on the LED color change. (Hint: the LED lights will not glow when the intensity of the field does not change.)

Discussion

  1. Equipment
  2. Green Light
  3. Changing from Green light to Red light
  4. Red light

B-I8 : Faraday's Flashlight

Unit

Induction

Purpose

To demonstrate Faraday's law of induction

Equipment

  1. Faraday's flashlight

Suggestions

Shake the flashlight horizontally for approximately 30 seconds for best results.

Discussion

B-I9 : Small Jumping Rings

Unit

Solenoid/Faraday's Law

Purpose

Illustrate mag. field of a solenoid.

Equipment

  1. Ring launcher
  2. Assorted Rings
  3. Aluminum Ring with a cut

Suggestions

  1. Launch various rings (thin aluminum ring is the best jumper)
  2. Show that the ring with a cut does not jump.

Discussion

Discuss Faraday's Law; introduce concept of inductance.

  1. Equipment
  2. Launching a large copper ring
  3. Aluminum ring with a cut

B-I10 : Large Jumping Rings

Unit

Solenoid/Faraday's Law

Purpose

Demonstrate mag. field of a solenoid, induced magnetic field, inductance.

Equipment

  1. Ring Launcher
  2. Small/large copper rings
  3. Small/large aluminum rings
  4. Aluminum ring with a cut

Suggestions

  1. Launch various rings (thin aluminum ring is the best jumper).
  2. Show the non-effect for a ring with a cut
  3. Levitate a ring; point out Joule's heating in a ring

Discussion

Discuss Faraday's Law; introduce concepts of inductance.

1. Equipment
2. Launching a large aluminum ring
3. Launching a small aluminum ring
4. Launching a large copper ring
5. Levitated small brass rings
6. Aluminum ring with a cut

7. Eqipment
8. Coil with a bulb neer the core (lights on)
9. Coil with a bulb neer the core (lights off)
10. Light with many coils closer to the magnet with the light off.
11. Flexable coil with one turn arround the core
12. Flexable coil with many turns arround the core

B-I11 : Resonance Demonstrator

Unit

RLC Circuits

Purpose

To demonstrate resonance in an electrical circuit

Equipment

  1. Resonance demonstrator

Suggestions

Experiment with both the position of the inductor core and the capacitor

Discussion

  1. Circuit out of resonance (low inductance)
  2. Circuit Resonating (low inductance, capacitor shorted)
  3. Circuit Resonating (high inductance)
  4. Circuit out of resonance (high inductance, capacitor shorted)

B-I12 : Magnetic "Levitation"

Unit

Lenz's Law

Purpose

To show the interaction between a magnet and it's induced magnetic field.

Equipment

  1. Conducting plate
  2. Strong magnet
  3. Dish
  4. Liquid Nitrogen

Suggestions

Allow the disk to cool for ~20 minutes before using. A range of magnets will work, try different sizes and shapes to see the effects. Make sure the experiment is performed on a non-magnetic surface.

Caution: Neodymium magnets are very strong and brittle, they can chip easily. 
Use caution handling the cooled disk and container.

Discussion

  1. Equipment
  2. Large magnet rebounding from the copper.
  3. Small magnet hovering over the copper.

B-I13 : Meisner Effect

Unit

Superconductivity and Magnetic Fields

Purpose

To illustrate the Meisner effect, the expulsion of magnetic field lines by a superconductor

Equipment

  1. Superconducting sample
  2. Small cube magnet
  3. Dish
  4. Plastic tweezers
  5. Liquid Nitrogen

Suggestions

Allow the superconductor to cool for ~5 minutes before using. Store the disk and magnet in a dessicator after use.

Discussion

  1. Equipment
  2. Spinning the magnet with the tweezers
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