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.
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.