Elementary physics

Preface

This book is intended for use in the last years of the high school. It supposes a knowledge of elementary algebra. In a few paragraphs geometrical theorems are referred to, but these may be omitted without breaking the continuity of the text The text is intended to accompany experiments by the instructor before the class, and to be supplemented by laboratory work on the part of the students.

Physics embraces a field so wide and so crowded with important facts and principles that it is hard to decide what to include and what to omit. The selection here offered is based upon fifteen years* experience in teaching physics to students of high-school grade. The writer has aimed to omit nothing of prime importance which can be brought within the range of students of the grade for whom the book is intended. In selecting among matters of less importance, and in illustrating laws and principles, an effort has been made to choose, as far as possible, things with which the average student is likely to be somewhat familiar, or with which he may easily acquaint himself.

Many of the problems are based upon actual observation and measurement, and it is believed that none of them lead to impossible results.

The tables are taken, with little exception, from the compilation of physical tables published by the Smithsonian Institution.

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ly PREFACE

The writer is greatly indebted to Dr. Robert R. Tatnall, Assistant Professor of Physics at Northwestern University, who has critically examined the whole manuscript and made many valuable suggestions. A like acknowledgment is due to Dr. J. Franklin Meyer, Professor of Physics at State College, Pa., who has read a part of the manuscript.

L. B.

West Chester, 1908.

CHAPTER I. — Properties of Matter. PAGE

Introductory. Measurement. General Properties of Matter.

Law of Gravitation. Special Properties of Matter ... 9

CHAPTER II. — Force and Motion: Work and Energy

Kinds of Motion. Vectors. Composition and Resolution of Velocities and Displacements. Acceleration. Measurement of Forces. Newton's Laws of Motion. Equilibrium of Forces. Work and Energy. Moment of Inertia. Falling Bodies. Friction. Resistance of the Air. Formulae for Energy. The Pendulum. Elementary Machines ... 19

Media. Sounding Bodies. Speed of Sound. Reflection of Sound. Musical Sounds. Siren. Pitch. Loudness. Quality. Manometric Flames. Forced and Sympathetic Vibrations. Resonance. Interference. Beats. Pipes. Strings. Chladni's Figures. Voice. Hearing. Musical Scales. Harmony and Discord 137

CHAPTER VII.— Light

Nature of Light. Media. Theories of Light. Shadows. Speed of Light. Photometry. Reflection. Visual Angle. Plane Mirrors. Concave Mirrors. Convex Mirrors. Caustic. Refraction. Index. Total Reflection. Lenses. Images by Convex Lens. Optical Instruments. The Eye. Color. Solar Spectrum. Bright Line Spectrum. Absorption Spectrum. Spectroscope. Achromatic Lens. Rainbow. Complementary Colors. Colors of Opaque Objects. Interference. Diffraction. Polarization 167

CHAPTER VIII.— Heat

Heat a Form of Energy. Temperature. Thermometers. Expansion by Heat. Law of Charles. Specific Heat. Mechanical Equivalent of "Heat. Change of State. Latent Heat. Clouds. Vapor Pressure. Critical Temperatures. Ice Machines. Distribution of Hea+ Conduction. Radiation. Heat Engines 218

CONTENTS Vli

CHAPTER IX.— Magnetism. PAGE

Natural Magnets. Poles. Law of Magnetic Force. Unit Pole. Nature of Magnetism. Lines of Magnetic Force. The Earth a Magnet. The Compass. Declination. Dip .... 258

CHAPTER X.— Static Electricity

Electrification. Attraction and Repulsion. Positive and Negative. Conductors and Insulators. Charged Bodies. Gold-leaf Electroscope. Induction. Points. Unit Charge. Potential. Electrophorus. Influence Machines. Condensers. Lightning . 270

CHAPTER XI.— Current Electricity

Simple Cell. Polarization. Electrolysis. Gravity Cell. Leclanche Cell. Storage Cells. Resistance. Effect of Temperature on Resistance. Cell Arrangement. Ohm's Law. Heat Developed. Magnetic Effects of Currents. Galvanometers. Voltmeters and Amperemeters. Electro-magnets. Thermal Currents. Induced Currents. Lenz's Law. Induction Coil. Self-induction. Magneto Machine. Commutator. Armatures. The Dynamo. Alternators. Applications of Electric Currents. Plating. The Arc. Incandescent Lamps. Transformer. The Telegraph. Motors. The Telephone. Electric Measurements „ 286