
Lecture Description
All stuff is electric in nature! Everything is electric! Stones - stars -all living things. For all stuff is made up of atoms - and atoms are made up of charged particles.
A - It was THALES in ancient Greece who first reported the strange behavior wherein amber when rubbed acquired the property of attracting unto itself light bits of straw and dust. THIS was the foundation of all electrical science. So we show these things with a rubber rod rubbed with fur. Cork dust is quickly ''attracted".. AND - quite as important - the dust is soon DRIVEN AWAY. It is very important to UNDERSTAND these actions. Coulomb forces are strong and ever-present.
B - We show similar effects with a pocket-comb We do work by rubbing the comb on something. Charges are separated. Electric energy is thus made available.
C - We define the charge on a rubber rod when it is rubbed with fur as NEGATIVE. The fur therefore has an equal measure of POSITIVE charge. Similarly - a glass rod rubbed with silk has on it - by definition - a POSITIVE charge. To determine the nature of an unknown charge we use an ELECTROSCOPE which we can charge by CONDUCTION or by INDUCTION. The sequence of operations in both is very important. When an electroscope is charged by CONduction the charge on the instrument is that of the charger. When an electroscope is charged by INduction the charge on it is opposite that of the inducer.
D - Pith balls hang on silk strings. They are first electrically or electrostatically NEUTRAL. We now approach them with a charged rod. They flee swiftly to the rod - touch it - hang on a moment - and soon swiftly swing away_ They first FEEL the effects of induction. Then on contact they are charged by conduction. Having now the same charge as the rod they flee from the rod and from each other.
E - And where will an electroscope be unaffected by an electric field?
Answer: in a closed metal conductor - as in a wire cage. And thus we learn what places are safe in a lightning storm.
F - To show how ENORMOUS these electrostatic forces CAN be: Place a long 2 by 4 or a heavy clean plank astride a watch-glass so it can turn freely. Stroke one end of the 2 by 4 swiftly with a cat's fur. Also charge a rubber rod with fur. Now approach the end of the log with the charged rod. It turns! The electrostatic forces are really massive. It is an interesting exercise to compare these electric forces with the gravitational forces.
Finally this must be said: Although the operations we have done in this Lesson seem trivial they are fundamental to the science of ELECTRICITY and indeed constitute the FOUNDATIONS of all electrical science.
Course Index
- The Idea of the Center of Gravity
- Newton's First Law of Motion: Inertia
- Newton's Second Law of Motion: The Elevator Problem
- Newton's Third Law of Motion: Momentum
- Energy and Momentum
- Concerning Falling Bodies & Projectiles
- The Simple Pendulum and Other Oscillating Things
- Adventures with Bernoulli: Bernoulli's Principle
- Soap Bubbles and Soap Films
- Atmospheric Pressure
- Centrifugal Force and Other Strange Matters
- The Strange Behavior of Rolling Things
- Archimedes' Principle
- Pascal's Principle: The Properties of Liquids
- Levers, Inclines Planes, Geared-wheels and Other Machines
- The Ideas of Heat and Temperature
- Thermometric Properties and Processes
- How to Produce Heat Energy
- Thermal Expansion of Stuff: Solids
- Thermal Expansion of Stuff: Gases & Liquids
- The Strange Thermal Behavior of Ice and Water
- Heat Energy Transfer by Conduction
- Heat Energy Transfer by Convection
- Heat Energy Transfer by Radiation
- Evaporation, Boiling, Freezing: A Dramatic Adventure
- Miscellaneous Adventures in Heat
- The Drama in Real Cold Stuff: Liquid Nitrogen
- The Physics of Toys: Mechanical
- The Physics of Toys: Acoustic and Thermal
- Waves: Kinds of Properties
- Sound Waves: Sources of Sound & Pitch and Frequency
- Vibrating Bars and Strings: The Phenomenon of Beats
- Resonance: Forced Vibrations
- Sounding Pipes
- Vibrating Rods and Plates
- Miscellaneous Adventures in Sound
- Electrostatic Phenomena: Foundations of Electricity
- Electrostatic Toys, Part 1
- Electrostatic Toys, Part 2
- Adventures with Electric Charges
- Adventures in Magnetism
- Ways to "Produce" Electricity
- Properties and Effects of Electric Currents
- Adventures in Electromagnetism
- Further Adventures in Electromagnetism
- Miscellaneous and Wondrous Things in E&M
Course Description
Demonstrations in Physics was an educational science series produced in Australia by ABC Television in 1969. The series was hosted by American scientist Julius Sumner Miller, who demonstrated experiments involving various disciplines in the world of physics. The series was also released in the United States under the title Science Demonstrations.
This program was a series of 45 shows (approximately 15 minutes each) on various topics in physics, organized into 3 units: Mechanics; Heat and Temperature / Toys; and Waves and Sound / Electricity and Magnetism.