Chapter XX: Current Strength 142

Strength of Current.--Unit of Current Strength; The
Ampere.--Measurement of Current Strength.--The Tangent
Galvanometer.--The Ammeter.--The Voltameter.--Unit of Quantity;
The Coulomb.--Electrical Horse-power; The Watt.--Ohm's
Law.--Internal Resistance and Current Strength.--Exp. 142,
Having a cell with large plates, to find how the strength of the
current is affected by changes in the position of the plates, the
external resistance being small.--Exp. 143, Same as Exp. 142,
but with small plates.--Exp. 144, To find whether the changes
in current strength, due to changes in internal resistance,
are as great when the external resistance is large, as they
are when the external resistance is small.--Discussion, with
examples.--Arrangement of Cells and Current Strength.--Cells in
Series.--Cells Abreast.--Exp. 145, To find the best way to join
two similar cells when the external resistance is small.--Exp.
146, To find the best way to join two similar cells when the
external resistance is large.--Best Arrangement of Cells.

CHAPTER XXI. CHEMICAL EFFECTS OF THE ELECTRIC
CURRENT 151

Chemical Action and Electricity.--Electrolysis.--Exp.
147, To study the electrolysis of water.--Composition
of Water.--Electromotive Force of Polarization.--Exp.
148, To coat iron with copper.--Exp. 149, To
study the electrolysis of a solution of copper
sulphate.--Electroplating.--Exp. 150, To study the chemistry of
electroplating.--Discussion.--Electrotyping.--Voltameters.--Exp.
151, To study the construction and action of a simple "storage"
cell.--Secondary or Storage Cells.

CHAPTER XXII. ELECTROMAGNETISM 158

Electromagnetism.--Exp. 152, To study the lines of force about
a straight wire carrying a current.--Ampere's Rule.--Lines
of Force About Parallel Wires.--Exp. 153, To study the
lines of force about a coil of wire like that upon the
galvanoscope.--Exp. 154, To study the magnetic field about a
small coil of wire.--Coils.--Polarity of Coils.--Exp. 155, To
test the attracting and "sucking" power of a magnetized coil
or helix.--Exp. 156, To find whether a piece of steel can be
permanently magnetized by an electric current.--Exp. 157, To
study the effect of a piece of iron placed inside of a magnetized
coil of wire.

CHAPTER XXIII. ELECTROMAGNETS 165

Electromagnets.--Cores of Electromagnets.--Exps. 158-163,
To study straight electromagnets; Lifting power; Residual
magnetism of core; Magnetic tick; Magnetic figures; Magnetic
field.--Horseshoe Electromagnets.--Use of Yoke.--Experimental
Magnets.--Method of Joining Coils.--Exps. 164-173, To study
horseshoe electromagnets; To test the poles; To study the
inductive action of one core upon the other; Magnetic figures;
Permanent Magnetic Figures; Lifting power; Residual magnetism
when magnetic circuit is closed.--Closed Magnetic Circuits.

CHAPTER XXIV. THERMOELECTRICITY 175

Exp. 174, To find whether electricity can be produced by
heat.--Home-made Thermopile.--Thermoelectricity.--Peltier
Effect.--Thermopiles.