Lecture Demos: Electricity and Magnetism

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Meissner Effect

Meissner Effect

This demonstrates levitation of a magnet above a high-temperature superconductor.

PIRA Code(s): 
5G50.50
Set up time: 
2 minutes
Physics and Science Concepts: 
Superconductivity, Magnetic Materials
Operation: 
A superconductor disc is placed in a styrofoam dish and liquid nitrogen is added to the dish. A small magnet is placed on top and within a few seconds it begins to levitate.
Safety: 
Liquid Nitrogen can be obtained from the machine shop.

Fluorescent Lamp Circuit

Fluorescent Lamp Circuit

Fluorescent lamp circuit mounted on a board can be used manually or automatically.

PIRA Code(s): 
5L20.14
Set up time: 
1 minute
Physics and Science Concepts: 
AC Circuits
Operation: 
Plug in the circuit. Flip the switch that says line and then put the lever to the automatic side for the whole lamp to light up. Flip the line switch again and move the lever to the middle. Put the line switch on again and move the lever to the manual side. This will heat up the filament. Then move the lever a little away from the manual side for the entire light to be lit.
Safety: 
None

Jumping Ring

 Jumping Ring

This experiment uses a coil of wire with a solid iron core inside the coil. When the switch is closed and AC current flows through the coil, the continuously changing magnetic field create eddy currents inside of metal rings place over the iron core. The rings will jump different heights depending on their thickness. Sparks can be created with a copper coil, while a light bulb attached to a coil will shine. Resistive heating can be demonstrated by holding the full rings down and feeling them heat up.

PIRA Code(s): 
5K20.30
Set up time: 
2 minutes
Physics and Science Concepts: 
Lenz law, Electromagnetic Induction, Eddy Currents
Operation: 
Set up the apparatus so that the silver pole sticks above the platform a few inches. Place a full ring around the tube and turn the apparatus on. This will make the ring jump into the air. Turn off the machine then, place the split ring around the pole, turn on the machine and this will not do anything. Resistive heating can be demonstrated by holding the full rings down and feeling them heat up. Next, turn off the machine, place the copper coil around the pole and press down on the copper rod sticking off the coil to create sparks. Also, place the light bulb circuit ring against the flat top part of the pole and watch it light up.
Safety: 
Do not place apparatus directly under a light. Do not stand above machine when the rings jump. Do not hold the full ring down too long, you may get burned.

Eddy Current Pendulum

Eddy Current Pendulum

A pendulum swings between the poles of a large permanent magnet. The full copper sheet swings a few times then stops in between the magnet. The comb copper sheet is unaffected by the magnetic and swing freely because the gaps in this sheet do not allow significant eddy currents to flow.

PIRA Code(s): 
5K20.10
Set up time: 
5 minutes
Physics and Science Concepts: 
Electromagnetic Induction, Eddy Currents
Operation: 
Set up the pole with the right angle clamp and pendulum. Place the permanent magnet so that the copper sheet is in between the two magnet sides. Swing the full copper sheet swing through the magnet. Watch as it damps out quickly. The, flip the pendulum so that the copper comb side is swinging through the magnet. Watch how it swings as if the magnet is not even there.
Safety: 
Stand to the side of the pendulum as it swings, not directly in the path.

Induction Coil, Magnet, Galvanometer

Induction Coil, Magnet, Galvanometer

A galvanometer is activated by placing a magnet near an induction coil and rotating the induction coil.

PIRA Code(s): 
5K10.20
Set up time: 
1 minute
Physics and Science Concepts: 
Electromagnetic Induction, Electricity and Magnetism
Operation: 
Hook the leads from the galvanometer to the induction coil. Place a magnet in front of the coil. Turn the crank and the needle on the galvanometer should move. The connection between the galvanometer and the loop changes polarity every half turn.
Safety: 
Magnet is extremely strong so do not place metal objects near it.

CRT with a Magnet

CRT with a Magnet

A bar magnet can deflect the electron beam in a cathode ray tube (CRT) according to the right-hand rule. This is due to the force a magnetic field has on a moving charge.

PIRA Code(s): 
5H30.10
Set up time: 
2 minutes
Physics and Science Concepts: 
Magnetic Fields and Forces
Operation: 
Plug in the cathode ray tube. Deflect the beam of the CRT by holding a permanent magnet near the edge of the tube. If the beam disappears, you are holding the magnet too close. Also, you can deflect the beam by attaching a battery to the binding posts and adjusting the variable control knob.
Safety: 
None

Magnet and Iron Filings

Magnet and Iron Filings

A bar magnet is positioned beneath a piece of paper on an overhead projector. Iron filings sprinkled on the paper will show the magnetic field. The overhead projector displays the image.

PIRA Code(s): 
5H10.30
Set up time: 
3 minutes
Physics and Science Concepts: 
Magnetic Fields and Forces
Operation: 
Place the magnet under the piece of paper and on the overhead. Sprinkle iron filings over the magnet and the filings should align with the magnetic field.
Safety: 
An overhead can be obtained from demonstration 9A36.10.

DC Series and Parallel light bulbs

DC Series and Parallel light bulbs

Four light bulbs with clips can be wired in series or parallel circuits using two metal rods attached to a 6V battery.

PIRA Code(s): 
5F20.50
Set up time: 
5 minutes
Physics and Science Concepts: 
Parallel and series circuits
Operation: 
First, attach the metal rods to the battery by unscrewing the black caps and place the rods around the screws. Then replace the caps. Next, clip one light bulb on the metal rods to show a circuit with a single light bulb. To show series circuits, clip two bulbs together and place the end of each clip on opposite rods. To show parallel circuits, clip each bulb separately to the rods. The bulbs in series will glow less brightly than the bulbs in parallel.
Safety: 
The ends of the rods pose an eye hazard.

Voltaic Cell

 Voltaic Cell

A voltaic cell is made with copper and zinc electrodes in a sulfuric acid solution.

PIRA Code(s): 
5E40.20
Set up time: 
1 minute
Physics and Science Concepts: 
Electromotive Force and Current
Operation: 
Pour sulfuric acid into the glass container. Wait 5 minutes for the reaction to take place between the dissimilar metals. Place the voltmeter on the overhead and display the voltage generated in the cell.
Safety: 
Be careful around acid. Gloves and goggles should be worn when handling acid.

Series and Parallel Leyden Jars

Series and Parallel  Leyden Jars

Leyden jars are charged by an electrostatic generator connected to the inner electrode while the outer plate is grounded. The inner and outer surfaces of the jar store equal but opposite charges.

PIRA Code(s): 
5C30.40
Set up time: 
5 minutes
Physics and Science Concepts: 
Electricity and Magnetism, Capacitance
Operation: 
Jars can be charged with either the Wimshurst generator (5A50.10) or Van de Graaf generator (5A50.30). Charge Leyden jars in parallel and discharge, charge in parallel again and connect in series before discharging. The intensity of the sparks as well as their duration is much greater for the series connection.
Safety: 
Do not touch the charged capacitor. Make sure the jar is discharged before storing or touching.

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