Preface ........................................................ ix
Chapter I. Magnetism ............................................ 1
Historical—experiments with bar magnets-methods of
magnetising - theories of magnetism - modification of the
molecular theory of magnetism - magnetic induction -
the magnetic field - why the lines of force of a bar magnet
have their curved shape - properties of lines of force -
the effect of unmagnetised iron in a magnetic field -
the earth is a magnet.
Chapter II. Electricity ........................................ 19
Discovery of electricity - two kinds of electricity -
the flow of electricity - conductors and insulators -
the first electroscopes - the gold-leaf electroscope -
testing insulators - the charge on the rubber -
electrostatic induction - fluid theories - charging by
induction - explanation of the attraction of small objects -
charging an electroscope by induction - effect of an earthed
conductor on a charged electroscope - the electrophorus - the
modern era - the constitution of matter - the hydrogen atom -
atoms of the rest of the elements - electrification by
rubbing - conductors and insulators - Galvani and Volta
- the simple cell - historical.
Chapter III. Ohm's Law ......................................... 38
The water analogy - the electric supply mains in a house -
Ohm's law - small and large units - -measurement of
resistance - resistances in series and in parallel - proof
of the formulae - Ohm's law applied to a complete circuit -
arrangement of cells.
Chapter IV. The Magnetic Effect of an Electric Current ......... 54
Oersted's experiment - the magnetic field due to a current
in a straight wire - Maxwell's corkscrew law - the magnetic
field due to a circular coil - the solenoid - the magnetic
field inside a solenoid - magnetising action of a solenoid -
the electromagnet - uses of the electromagnet -
the single-stroke signalling bell - the trembler bell -
indicators - the relay - automatic railway signalling -
the full block overlap system.
Chapter V. Electrodynamics ..................................... 74
The force on a wire carrying a current in a magnetic field -
Fleming's left-hand rule - explanation by means of lines of
force - the principle of the electric motor -
the commutator - the armature - the field magnet -
the Einthoven string galvanometer - the forces between two
wires carrying currents.
Chapter VI. Galvanometers, Ammeters and Voltmeters ............. 87
The first galvanometer - other moving-magnet galvanometers -
the moving-coil galvanometer - the moving-iron galvanometer -
the hot-wire galvanometer - the sensitivity of
a galvanometer - decreasing sensitivity by means of a shunt -
ammeters - voltmeters.
Chapter VII. Electrolysis ..................................... 102
Nicholson and Carlisle and Davy - terminology -
the electrolysis of a solution of hydrochloric acid -
the electrolysis of copper sulphate solution -
the electrolysis of acidulated water - the electrolysis
of sodium-sulphate solution - Faraday's laws of
electrolysis - the electrochemical equivalent - experimental
determination of the electrochemical equivalent of copper -
measuring current by means of a voltameter' - theories of
electrolysis - the ionic theory - explanation of
Faraday's laws - electroplating - electrotypes -
the manufacture of aluminium.
Chapter VIII. Cells ........................................... 124
The simple voltaic cell - polarisation - local action -
the Daniell cell - different metals used in cells -
the Leclanché cell - the dry cell - the Gordon magnesium
cell - the action inside a voltaic cell - the accumulator -
charging and discharging - practical details - the drop in
potential difference when a cell delivers a current - the
general circuit.
Chapter IX. Measurement of Resistance and Potential
Difference .................................................... 142
Methods of measuring resistance: 1, method of substitution;
2, ammeter and voltmeter method; 8. the Wheats tone bridge -
the metre bridge - locating a fault in a line - resistivity -
the effect of temperature on resistance - the potentiometer -
comparing the electromotive forces of two cells -
the standard cell - example.
Chapter X. Electrical Energy .................................. 161
The work done by an electric current - power - the power
in an electric lamp - buying electrical energy - the heating
effect of an electric current - the work of Joule -
experimental determination of the mechanical equivalent of
heat - electric heating - electric lamps - fuses -
the wiring of a house - the electric arc - electric
welding - the electric furnace.
Chapter XI. Electromagnetic Induction ......................... 181
Inducing a current - the induced electromotive force and the
induced current - Faraday's theory - the strength of the
induced electromotive force - the direction of the induced
current - inducing a current in a coil with a bar magnet -
the direction of the induced current - Lenz's law -
Fleming's right-hand rule - mutual induction - the induction
coil - slip rings or commutator - the principle of the
dynamo - the way the strength of the current varies as the
coil is rotated - eddy currents - Michael Faraday -
Faraday's discovery of electromagnetic induction -
Faraday's other discoveries.
Chapter XII. Dynamos and Motors ............................... 207
The reverse motor effect in a dynamo - the reverse dynamo
effect of a motor - self-adjusting property of an electric
motor - series and shunt-wound motors - starting
resistances - the drum-wound armature - the alternating
current generator - frequency - power stations.
Chapter XIII. The Grid ........................................ 226
Introductory - power transmission - advantages of
alternating current over direct current - the transformer -
power transformers - transformer design - the overhead
lines - substations - protective gear - metering - control -
three-phase alternating current - balancing - advantages
of three-phase alternating current.
Chapter XIV. Electric Telegraphy and Telephony ................ 251
The first electric telegraphs in England - Samuel Morse -
the Morse code - the Morse sounder - the Morse key - simple
telegraph circuit - the use of the relay - duplex and
multiplex telegraphy - automatic telegraphic apparatus -
the Creed high-speed automatic printing telegraph - the
laying of the first Atlantic cable - modern submarine
cables - the siphon recorder - telephony - Bell's
telephone - the microphone - the modern telephone
transmitter - the Edison telephone circuit - the exchange -
the automatic system
Chapter XV. The Measurement of Magnetism ...................... 280
The inverse square law - the centimetre-gramme-second
system of units - unit pole - the strength of a magnetic
field - intense magnetic fields - determination of pole
strength by plotting lines of force due to a single pole -
determination of pole strength by plotting lines of force of
a bar magnet with its N. pole pointing S. - the moment of
a magnet - the principle of the deflection magnetometer -
details of the instrument - use of the deflection
magnetometer - the vibration magnetometer - other factors
affecting the rate of vibration of a magnet - end-on
position - broadside position - any position.
Chapter XVI. The Earth's Magnetism ............................ 302
Declination - dip - the earth's field - determination of
declination - determination of dip - the charting of the
magnetic elements throughout the world - variation of dip
over the earth's surface - variation of declination over
the earth's surface - secular variations - theories of the
origin of the earth's magnetism - the mariner's compass -
deviations of the compass.
Chapter XVII. The Measurement of Electricity .................. 321
The electromagnetic unit of current - definition -
the tangent galvanometer - to check the reading of an
ammeter using a tangent galvanometer - theoretical
definitions of the volt and the ohm - practical standards.
Chapter XVIII. Electrostatics ................................. 328
Charging by rubbing - distribution of charge on conductors:
(a) on surface, (b) accumulates at more curved parts - the
action of points - collecting charges by points - Van de
Graaffs generator - thunder and lightning - lightning
conductors - how the clouds become charged - electric
potential - the gold-leaf electroscope measures potential
rather than charge - the effect of earthing the case of an
electroscope - the potential throughout a charged conductor
is uniform - the electric field - properties of lines of
electric force - use of lines of force - Faraday's
ice-pail experiment - capacitance or capacity - the
condenser - on what does the capacitance of a condenser
depend? - the Leyden jar - the identity of static and
current electricity.
Chapter XIX. The Modern Era ................................... 357
The discharge of electricity through rarefied gases - neon
tubes - cathode rays - X-rays - gas tubes - the Coolidge
tube - the ionisation of gases - radioactivity - the energy
emitted by radium - the disintegration theory - artificial
disintegration.
Answers to Questions .......................................... 375
Index ......................................................... 379
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