Ways to  
Ways to "Produce" Electricity
by Prof. Miller
Video Lecture 42 of 46
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Date Added: February 5, 2015

Lecture Description

It is to be noted that the word "PRODUCE" is in quotation marks. The reason is this: We do not really produce electricity. Electric charges already exist. They are in everything. All we do is separate them. This separation requires WORK and this work produces a difference of potential.

A - We show some commonplace events: A sliver of zinc and a sliver of
copper are lodged in a lemon. Here we have TWO DIFFERENT METALS in an electrolyte. These constitute a VOLTAIC CELL.. .after Alessandro Volta.

B - Two different metals in my mouth constitute a Voltaic Cell. And some important matters here arise: If the fillings in my teeth are different metals we have a very bad electrolytic cell and the chemical action can be destructive!

C - The plates in a storage battery - as the one in your car - are ALL
LEAD (Pb). How then can we get a current out of this? A difference of potential? An emf ? A voltaic cell requires TWO different metals. ANSWER: The plates are indeed all lead but when the battery is charged the charging mechanism makes the plates different! Thus the requirement of a voltaic cell is met.

D - Two different wires - two different metals - joined at their ends - constitute a thermocouple. If now one junction is kept at one temperature and the other junction at another temperature an electric current arises. This is called a thermal EMF.

E - The so-called DRY CELL is NOT dry! The center pole is a carbon rod -and this is the positive terminal. The can containing all the stuff is zinc. This satisfies the requirements for a voltaic cell. The sticky pasty stuff inside is WET.

F - In 1831 Michael Faraday discovered that a magnetic field can produce an electric current. This followed Oersted's discovery in 1820 that a current bearing conductor gives rise to a magnetic field. So - if a magnet is moved in and out of a coil an EMF arises. MOTION of the magnet or of the coil is required. Thus we have the magneto-electric generator where a coil of wire is turned in a magnetic field and enough current is generated to light a lamp.

G - On the matter of a voltaic cell: We have two different metals in an electrolyte. The emf is governed by the nature of the metals and by the nature of the electrolyte. The SIZE of the plates or the amount of the electrolyte change nothing as far as EMF goes. A huge vat with slabs as big as barn doors and a droplet of the electrolyte with tiny metal slivers give the same EMF. However - the bigger the system the longer the life of the system - that is - the longer the energy producing life. AND the larger the current available. This is all tied up with Ohm's Law.

H - For the magneto-electric generator: it must be observed that the current produced is an alternating current - a current which surges first this way than that. This is made evident by the flicker of the lamp energized this way.

Course Index

  1. The Idea of the Center of Gravity
  2. Newton's First Law of Motion: Inertia
  3. Newton's Second Law of Motion: The Elevator Problem
  4. Newton's Third Law of Motion: Momentum
  5. Energy and Momentum
  6. Concerning Falling Bodies & Projectiles
  7. The Simple Pendulum and Other Oscillating Things
  8. Adventures with Bernoulli: Bernoulli's Principle
  9. Soap Bubbles and Soap Films
  10. Atmospheric Pressure
  11. Centrifugal Force and Other Strange Matters
  12. The Strange Behavior of Rolling Things
  13. Archimedes' Principle
  14. Pascal's Principle: The Properties of Liquids
  15. Levers, Inclines Planes, Geared-wheels and Other Machines
  16. The Ideas of Heat and Temperature
  17. Thermometric Properties and Processes
  18. How to Produce Heat Energy
  19. Thermal Expansion of Stuff: Solids
  20. Thermal Expansion of Stuff: Gases & Liquids
  21. The Strange Thermal Behavior of Ice and Water
  22. Heat Energy Transfer by Conduction
  23. Heat Energy Transfer by Convection
  24. Heat Energy Transfer by Radiation
  25. Evaporation, Boiling, Freezing: A Dramatic Adventure
  26. Miscellaneous Adventures in Heat
  27. The Drama in Real Cold Stuff: Liquid Nitrogen
  28. The Physics of Toys: Mechanical
  29. The Physics of Toys: Acoustic and Thermal
  30. Waves: Kinds of Properties
  31. Sound Waves: Sources of Sound & Pitch and Frequency
  32. Vibrating Bars and Strings: The Phenomenon of Beats
  33. Resonance: Forced Vibrations
  34. Sounding Pipes
  35. Vibrating Rods and Plates
  36. Miscellaneous Adventures in Sound
  37. Electrostatic Phenomena: Foundations of Electricity
  38. Electrostatic Toys, Part 1
  39. Electrostatic Toys, Part 2
  40. Adventures with Electric Charges
  41. Adventures in Magnetism
  42. Ways to "Produce" Electricity
  43. Properties and Effects of Electric Currents
  44. Adventures in Electromagnetism
  45. Further Adventures in Electromagnetism
  46. 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.

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