Physics Lecture Demonstrations

Demonstrations suggested for the text
Electricity and Magnetism, 2nd. ed., by
Edward M. Purcell

Revised Tue Jan 21 08:42:31 2003

Chapter1--Electrostatics: Charges and Fields

EM-a1a Frictional Electricity An electroscope is charged using charged rods.
EM-a2b Conductive Balls Two lightweight conducting spheres suspended by nylon thread can be used as charge indicators
EM-a5a Wimshurst Machine Generate sparks with a Wimhurst Machine, and explain its workings.
EM-a5b Van de Graaff Generator Describe the operation of the Van de Graaff and show sparks from the ball to a nearby grounded conductor.
EM-a5c Van de Graaff Generator--Sound The engine strains more and more as the charge on the dome increases.
M-r5a NaCl crystal model NaCl model made of wooden balls connected by metal sticks.
EM-b1b Hair on End Charge yourself with a Van de Graaff generator
EM-b1c Styrofoam Peanut Blowout Styrofoam peanuts in a box on top of the Van de Graaff fly out.
EM-b1e Tart Pan Blowoff Tart pans stacked on top of the Van de Graaff fly off.
EM-b1d Electric Field Visualizer Tiny fibers in a clear oil align in the direction of strong applied electric fields.

Chapter2--The Electric Potential

Chapter3--Electric Fields around Conductors

EM-a3a Conductors and Insulators Shows that charge can be transferred to an electroscope through conductors but not insulators
EM-a4b Charged Rods and Aluminum Can A charged rod can be used to pull a soda can by electrostatic induction
EM-b2a Faraday Bucket Show that charge resides on the outside of a hollow conductor.
EM-b2f Gauss with Electric Field Visualizer Tiny fibers in a clear oil that align in the direction of strong applied electric fields remain randomly oriented inside a charged ring.
EM-b2b Radio in a Cage Surround a radio by a Faraday cage and the signal goes away
EM-b3a Surface charge density - balls Separate two pairs of balls of different radius but same separation are attached to and charged simultaneously with the Wimhurst.
EM-b3c Charged Ovoid Use a proof plane and an electroscope to compare charge densities at different points on an egg-shaped conductor.
EM-b3g Lightning Rod Electrical arcing between two large metal spheres abruptly ceases when the lightning rod is touched to one.
EM-b3f Electric Wind with Van de Graaff A point attached to the Van de Graaff blows a hanging peice of cardboard.
EM-b3e Van de Graaff Pinwheel A pinwheel rotates on top of a van de Graaff generator.
EM-c1a Parallel Plate Capacitor Vary the spacing of a parallel plate capacitor attached to an electroscope.
EM-c1b Capacitance as a Function of Area The rotary plate capacitor is attached to the electroscope.
EM-c3a Explosive Capacitor Discharge Discharge a 10kV, 1uF capacitor through a thin wire or thick screwdriver
EM-c3b Bulb and 1 Farad Capacitor A large (1 Farad) capacitor is charged with a battery then discharged through a light bulb.

Chapter4--Electric Currents

EM-d1a Wire Resistivity Place 6V across a set of wires of different diameters and measure the currents.
EM-d2a Change of Resistance with Temperature A coil in series with a lamp is immersed in liquid nitrogen making the lamp glow brighter.
EM-d2b Carbon Resistor in Liquid Nitrogen Drop a resistor in liquid nitrogen and measure its resistance.
EM-d2c Conduction in Glass Heat a glass rod with a flame until its resistance is low enough to sustain conduction.
EM-d4a Jacob's Ladder An arc rises between rabbit ear electrodes attached to a high voltage source.
EM-e1a Thermocouple Show a thermocouple in operation
EM-f1a Resistor I-V characteristics Measure and graph the I-V characteristics for a resistor. The value of the resistance may be varied.
EM-f1b Resistance of a Wire Measure the potential drop along a wire
EM-f2a Series Circuit with Bulbs Show a series circuit of light bulbs
EM-f2b Parallel Circuit with Bulbs Show a parallel circuit of light bulbs
EM-f2c Series Parallel Combination Two bulbs in series with a power supply, and a third bulb in parallel with one of others.
EM-f1e Hot Dog Cooker Spike a hot dog with two nails and cook it.
EM-c3c Bulb, 1 Farad Capacitor, and DVM Monitor the discharge of a 1 Farad capacitor through a light bulb with a digital voltmeter.
EM-c3d Bulb, 1 Farad Capacitor, and oscilloscope Oscilloscope display of a 1 Farad capacitor discharging through a light bulb.
EM-f3c RC Time Constant on Scope Observe the RC decay from a variable gap capacitor and resistor using a square wave input and oscilloscope.

Chapter5--The Fields of Moving Charges

Chapter6--The Magnetic Field

EM-b1a Oscilloscope Show that an electron beam passing between charged, parallel plates is deflected using an oscilloscope.
EM-h1a Oersted Experiment Show that current in a wire deflects a compass needle.
EM-h3a e/m tube Deflect the beam in an e/m tube with magnets
EM-h4a Force Between Two Current Carrying Conductors Show on the overhead projector that long parallel wires with currents in the same (opposite) directions attract (repel).
EM-h4c AC and DC Lamps A magnet is brought near two carbon filament bulbs, one DC powered and one AC powered.
EM-h4b Force on Current-carrying wire A loop of wire swings to the side of a U-magnet's gap when connected to a current-limited power supply.
EM-h1k B-Field due to long straight wire Iron filings are sprinkled on a plexiglas plate through which a long vertical current-carrying wire passes.
EM-h1m B-Field due to single coil. Iron filings are sprinkled on a plexiglas plate through which a single loop of current-carrying wire is mounted
EM-h1n B-Field due to solenoid Iron filings are sprinkled on a plexiglas plate through which a current-carrying solenoid is mounted.
EM-h5a Galvanometer A magnet exerts a torque on a current-carrying coil.
EM-k4c Direct Current Motor Show and explain a DC motor running on batteries.
EM-m1b Hall Effect Measure the transverse potential difference between between the sides of silver or tungsten in crossed electric and magnetic fields

Chapter7--Electromagnetic Induction

EM-k1a Induction Coil and Magnet A magnet is moved in and out of a coil connected to a galvanometer
EM-k1b Induction with Coils and Battery Attach one coil to a galvanometer, another to a battery and tap switch. Use a core to increase coupling
EM-k2f Eddy Current Pendulum -- Classroom Swing solid. open-slotted, and closed-slotted paddles between the poles of a neodymium magnet.
EM-k2b Magnets and Eddy Tubes Drop magnet and a non-magnetic dummy down an aluminum tube.
EM-k2c Magnet and Copper Tube Drop magnet down a short length of straight copper tubing and watch it fall.
EM-k2d Jumping Rings A solid conducting ring sitting on a vertical solenoid jumps and a split ring doesn't
EM-k4e Handheld DC Motor Run the handheld DC generator with a 1.5 or 3 V battery
EM-k4a AC Generator Rotating a wire loop in a magnetic field generates an AC current in the loop.
EM-k4b DC Generator Generate a DC current by rotating a loop with a split-ring connection in a magnetic field.
EM-k4d Hand-held DC Generator Use the handheld generator to illuminate a bulb.
EM-k4f Hand-powered flashlight The Dynamo--a hand powered flashlight
EM-k3a Transformer Demonstrate step-up and step-down transformers.
EM-j1b Back EMF with light bulb Open the switch of a large coil with a light bulb in parallel
EM-j2a Series RL circuit: L/R charge/discharge "Charging" and "Discharging" of inductor shown with square wave and oscilloscope
EM-j2b Series RL circuit: L/R phase shifts Show phase shifts in a series RL circuit using the oscilloscope.
EM-j2c Variable Inductor A lamp in series or parallel with a variable inductor.

Chapter8--Alternating Current Circuits

EM-L2c non-driven LRC circuit oscillations Show the oscillations (ringing) when a charged capacitor is connected in series to an inductor and small resistor.
EM-L2a 60 Hz LRC circuit Shows the potential difference across the Capacitor and Inductor at resonance.
EM-L2b LRC circuit with function generator Show the voltage-to-current phase shift and amplitude peaking at resonance in a driven LRC circuit.
EM-L3a Bridge Rectifier with LEDs Operate a bridge rectifier with LEDs at low frequency
EM-m1a Diode I-V characteristics Circuit for measuring the I-V characteristics of a diode

Chapter9--Maxwell's Equations and Electromagnetic Waves

EM-n1c Microwave Standing Waves Use a microwave generator, detector, and metal sheet to show standing waves
EM-n1b Microwave Generation and Detection Show the generation and detection of microwaves including polarization
EM-n2a Tesla Coil Light a fluorescent lamp by holding it near a Tesla Coil
EM-n2b AM Radio Modulate the output of a function generator attached to an antenna and detect the output with a transistor radio
EM-n3a Microwave Transmission Insert different materials (wood, metal, plastic, metal grill of small holes, wet and dry cloths) in a microwave beam
O-h1a Polaroids on the Overhead Show polarization with two sheets of polaroid on the overhead
O-h1b Microwave Polarizing Filter Insert a grid of parallel wires (= cookie cooling rack) in a microwave beam and rotate the grid.

Chapter10--Electric Fields in Matter

EM-c2a Parallel Plate Capacitor with Dielectric Insert and remove a dielectric sheet from a charged parallel plate capacitor attached to an electroscope.
EM-a4c Deflection of stream of water A charged rod deflects a stream of water.
EM-e6a Piezoelectric Demonstrator Generate sparks by compressing a piezoelectric crystal.
O-h3q Demonstrating Strain with Crossed Polaroids A set of lucite shapes are stressed between crossed polaroids
O-h3a Karo Syrup Insert a beaker of liquid sugar between crossed polaroids.
O-h3p Calcite Crystals Use a polaroid filter to show the polarization of ordinary and extraordinary rays
EM-c2b Dissectable Capacitor This curious capacitor is charged, disassembled, passed around, assembled, and discharged with a spark.
EM-c2c Force on a dielectric Mineral oil climbs in the gap between parallel plates

Chapter11--Magnetic Fields in Matter

EM-g3b Paramagnetic Aluminum A small aluminum rod suspended by a thread in the gap of a powerful magnet aligns with the field.
EM-g3c Diamagnetic Glass A small glass rod suspended by a thread in the gap of a powerful magnet orients transverse to the magnetic field.
EM-g3a Paramagnetic Liquid Oxygen Liquid oxygen condensing from air drips into the gap of a strong magnet
EM-g3d Diamagnetic Levitator A small magnetic is suspended in mid-air between two diamagnetic graphite disks.
EM-g5a Meissner Effect Cool a superconductor and it will levitate and float a magnet.
EM-h1c Dip Needle A dip needle is used to show the inclination of the earth's field.
EM-h1d Magnet and Iron Filings -- 2D A small magnet on top of the magnetic domain model apparatus
EM-h1e Magnet and Iron Filings -- 3D A bar magnet surrounded in 3D by a clear acrylic tank filled with a liquid containing iron filings.
EM-h2c magnetic dipole in external B field Compare a magnetic dipole suspended by a spring in a uniform B field with a grad B field.
EM-h2f Torque balance with air bearing magnet Balance the magnetic torque on a dipole with a gravitational torque.
EM-h2d Precessing Magnetic Dipole A magnetic dipole floating in an air bearing precessess in a uniform B field.
EM-h2e Classical Magnetic Resonance Rotate a transverse magnetic field to "flip" the spin of a precessing magnetic dipole.
EM-h2a Magnets on Pivots One magnet is placed on a pivot. The other is used to attract or repel the first
EM-h2b Ring Magnets on a Pole Two or more ring magnets are placed on a vertical pole
EM-g1a Lodestone Show that the lodestone attracts small nails and paperclips.
EM-g2c Barkhausen effect A soft iron core is inserted into a coil inside a magnetic field and connected to an audio amplifier and speaker.
EM-g2a Magnetic Domain Model An array of small compasses shows domain structures
EM-g2b Hard vs. Soft magnetic materials A circular magnetic yoke connecting two wire coils is closed with soft and hard materials
EM-h1b Magnetic Permeability The height to which the jumping rings jumps depends on how far the yoke extends

Physics Lecture Demonstrations at the Department of Physics and Astronomy
The Johns Hopkins University