Electromotive Force and Current Topic

Electrolysis

Concept 2 demos

Hofmann electrolysis apparatus on a stand with graduated glass tubes showing yellow-green and violet solutions, connected via red and black leads to a Heathkit IP-32 power supply, with a bottle of sodium sulfate solution on the right

Electrolysis of Water (Hofmann Apparatus)

Electrolyzes water into hydrogen and oxygen using a Hofmann apparatus. Students observe the 2:1 volume ratio of H₂ to O₂ and pH-indicator color changes that reveal the different chemical environments …

Three views of the projection electrolysis apparatus: projected image showing gas collection chambers with electrodes (top left), full setup with horizontal projector and battery eliminator (top right), and close-up of cell mounted on projector (bottom)

Electrolysis of Water (Projection)

Projects the electrolysis of water onto a screen so the entire lecture hall can observe gas collection. Students see the 2:1 volume ratio of hydrogen to oxygen develop in real …

Cells and Batteries

Concept 6 demos

Person holding metal electrodes connected via alligator clips to a yellow-cased BK Test Bench 388A multimeter displaying .402 V

Voltage of a Human

Holding dissimilar metal electrodes (copper and zinc) creates a galvanic cell using the body's electrolytes, producing ~0.4 V. Volunteers can be wired in series to add voltages or in parallel …

Potato with copper and zinc strip electrodes connected via alligator clips to a yellow Test Bench 388A digital multimeter reading 0.363 V DC, on white paper

Organic Batteries

Demonstrates electrochemical cells using everyday produce. Students see how zinc and copper electrodes in acidic fruit or vegetables generate a measurable EMF through redox reactions, connecting chemical potential energy to …

BK Test Bench 388A multimeter displaying .567 V, connected via alligator clips to zinc and copper electrodes draped over the rim of a beaker containing cloudy salt water

Salt Water Battery

A zinc-copper cell in plain water reads only 300-400 mV due to high internal resistance from poor ionic conductivity. Adding salt dramatically increases conductivity, and the measured voltage jumps to …

Thermoelectricity

Concept 4 demos

Lecture bench setup with two simple thermocouples connected through a switch and shunt to a laser galvanometer mounted on a stand, with a projection surface visible at left

Simple Thermocouples

Demonstrates the Seebeck effect: heating a thermocouple junction generates an EMF, shown as a deflection on a laser galvanometer. Students observe direct conversion of thermal energy to electrical energy and …

Two photos: Top shows the thermocouple magnet mounted on heavy ring stands with a stack of 2 kg weights hanging from the armature and a bench torch positioned nearby. Bottom shows a close-up of the copper bar and torch heating area with a University of Colorado inventory label.

Thermocouple Magnet

A thermocouple heated by a torch and cooled by running water generates enough Seebeck-effect current through a coil to magnetize an iron core and support up to 10 kg of …

Two photos: Top shows close-up of the Peltier apparatus on a lab jack with thermometer wells and an analog projection thermometer. Bottom shows the full setup with battery eliminator at left, Peltier device on lab jack in center, and overhead projector at right.

Peltier Effect Apparatus

Demonstrates the Peltier effect: current through a thermoelectric junction produces simultaneous heating on one side and cooling on the other. Projection thermometers show the temperature divergence in real time. The …

Piezoelectricity

Concept 1 demo

Large milky-white quartz crystal chunk and smaller tan stone used as a striker

Quartz Sparks

Scraping quartz with a striker in a darkened room produces visible orange flashes from triboluminescence (light emitted when crystals fracture). While cataloged under piezoelectricity, the dominant effect is triboluminescence -- …