Fig. 5. AIR BLOWER FOR THOMSON'S DYNAMO.
Air Condenser.
A static condenser whose dielectric is air. The capacity of an air
condenser in farads is equal to
A / ( 4.452E12 * t )
in which A is the area of one sheet or sum of the areas of one set of
connected sheets in square inches and t is the thickness of the layer of
air separating them.
A convenient construction given by Ayrton consists in a pile of glass
plates P separated by little bits of glass F of known thickness, three
for each piece. Tin-foil T is pasted on both sides of each piece of
glass and the two coatings are connected. The tin-foil on each second
plate is smaller in area than that on the others. The plates are
connected in two sets, each set comprising every second plate. For A in
the formula the area of the set of smaller sheets of tin-foil is taken.
By this construction it will be seen that the glass does not act as the
dielectric, but only as a plane surface for attachment of the tin-foil.
Posts E E keep all in position. One set of sheets connects with the
binding post A, the other with B.
The capacity of any condenser with a dielectric of specific inductive
capacity i is given by the formula:
( i *A^1 ) / ( 4.452E12 * t1 )
The air condenser is used for determining the value of i for different
dielectrics.
Fig. 6. AIR CONDENSER.