Overview:
This 1898 book, “How Two Boys Made Their Own Electrical Apparatus,” by Thomas M. St. John, is a comprehensive guide for building basic electrical equipment using everyday materials. The book is a testament to the accessibility of science, as it encourages young readers to experiment and learn by building their own devices. St. John’s detailed instructions are accompanied by clear illustrations, making the process of building understandable even for those with limited experience.
The text covers a wide range of topics, from simple cells and batteries to more complex systems like induction coils, telegraph sets, and electric motors. The book also includes valuable information on tools, materials, and methods of construction, making it a complete resource for budding electricians.
Key findings:
- The book highlights the importance of using the correct materials and tools for building electrical apparatus, emphasizing the distinction between steel and soft iron, as well as the importance of insulation.
- It emphasizes the practicality of building simple but functional devices using readily available materials like tin, copper wire, and wood.
- The text emphasizes the importance of understanding the principles of electricity and magnetism for building and using electrical devices.
Learning:
- Cells and Batteries: Learn how to make simple carbon-zinc and experimental cells using household materials. Understand different types of battery fluids like sulphuric acid, bichromate solution, and vinegar. Discover the process of amalgamating zinc plates to prevent corrosion.
- Switches and Cut-outs: Learn how to make basic switches and cut-outs for controlling the flow of electricity in a circuit. Understand their use in various electrical devices.
- Binding-Posts and Connectors: Learn how to build different types of binding-posts and connectors for joining wires and apparatus.
- Permanent Magnets: Discover how to magnetize steel needles and other materials to create various types of magnets including bar magnets, horseshoe magnets, and flexible magnets.
- Electro-Magnets: Learn how to build simple and complex electromagnets using soft iron wire and insulated copper wire. Understand the importance of washers and insulation for optimal magnet construction.
- Induction Coils: Learn the construction of induction coils and their components like primary and secondary coils. Explore different methods for interrupting the current in an induction coil to produce a shock.
- Current Detectors and Galvanometers: Learn how to make basic current detectors using magnetic needles and coils. Understand the concept of an astatic needle and its use in sensitive detectors. Explore the construction and use of a tangent galvanometer.
- Telegraph Keys and Sounders: Learn how to build telegraph keys and sounders for sending and receiving messages. Understand the concept of a closed-circuit battery for telegraph lines. Explore the telegraph alphabet and learn how to send simple messages.
- Electric Bells and Buzzers: Learn the construction of electric bells and buzzers using electromagnets, vibrating armatures, and bells. Understand the principle of an automatic interrupter.
- Electric Motors: Learn how to build simple electric motors using electromagnets, armatures, commutators, and brushes. Understand the concepts of field magnets and armature magnets, as well as the role of the commutator in reversing the current direction.
Historical Context:
The text was written in 1898, a time when electricity was a rapidly developing field. The book reflects the excitement and innovation surrounding the discovery of electricity and its applications. While the book focuses on basic electrical devices, it reflects the burgeoning field of electrical engineering and the growing demand for skilled technicians.
Facts:
- Amalgamation prevents corrosion: Mercury, when applied to zinc plates, forms a protective layer that prevents the zinc from being eaten away by battery fluids.
- Iron is a good conductor of magnetic force: Soft iron, like that found in sheet tin, easily becomes magnetized and demagnetized, making it ideal for yokes and armatures in electromagnets.
- Static electricity can be stored: Materials like glass and rubber can hold a charge of static electricity when rubbed against each other, demonstrating the phenomenon of static electricity.
- Electric currents create magnetic fields: Passing an electric current through a wire creates a magnetic field around the wire, influencing the behavior of magnetic needles.
- Electromagnets are stronger than permanent magnets: Passing an electric current through a coil of wire wrapped around a soft iron core creates a strong magnetic field, stronger than that of a permanent magnet.
- Different materials have different resistance: Copper is a good conductor of electricity, while materials like German silver have much higher resistance.
- Electric currents can produce motion: The interaction between magnetic fields of electromagnets and armatures in electric motors creates rotational motion.
- Telegraph systems rely on opening and closing a circuit: Pressing a telegraph key opens and closes a circuit, sending electrical impulses to a distant receiver.
- Electric bells use vibrating armatures: When a current passes through an electromagnet in a bell, the armature is attracted, striking the bell, and then springs back to its original position, causing a continuous ringing sound.
Statistics:
- 9 feet 9 inches of No. 30 insulated copper wire: Represents 1 Ohm of resistance.
- 39 feet 1 inch of No. 24 insulated copper wire: Represents 1 Ohm of resistance.
- 235 feet of No. 20 annunciator wire: Weighs approximately 1 pound.
- 100 lbs. of No. 14 galvanized iron wire: Weighs approximately 1 mile of wire.
Terms:
- Amalgamation: The process of coating a metal, like zinc, with mercury to prevent corrosion.
- Armature: A piece of soft iron that becomes magnetized when placed near an electromagnet.
- Binding-post: A device used to make secure electrical connections between wires and components.
- Commutator: A device used in electric motors to reverse the direction of current flow in the armature.
- Core: The central part of an electromagnet, typically made of soft iron.
- Electromagnet: A magnet created by passing an electric current through a coil of wire wrapped around a soft iron core.
- Induction: The phenomenon where a magnetic field produced by a changing electric current induces a current in a nearby coil.
- Polarization: The buildup of hydrogen bubbles on the surface of a battery plate, reducing the battery’s effectiveness.
- Resistance: The opposition to the flow of electric current in a circuit.
Examples:
- Carbon-Zinc Cell: A simple cell made from carbon and zinc rods, using a bichromate solution as the battery fluid.
- Gravity Cell: A two-fluid cell where the liquids are separated by gravity, ideal for long-duration telegraph systems.
- Astatic Needle: A combination of two magnetic needles arranged so their poles are opposite, reducing the needle’s pointing power.
- Tangent Galvanometer: A galvanometer designed to measure the strength of an electric current based on the angle of deflection of a magnetic needle.
- Electric Bell: A device that uses a vibrating armature and a bell to produce a ringing sound.
- Electric Motor: A machine that converts electrical energy into mechanical motion.
- Induction Coil: A device that uses a primary and secondary coil to produce high-voltage electricity, often used for generating a shock.
Conclusion:
“How Two Boys Made Their Own Electrical Apparatus” is a treasure trove of information for anyone interested in exploring the world of electricity. St. John’s clear instructions and practical advice empower readers to build their own electrical devices, fostering both hands-on learning and a deep understanding of fundamental electrical concepts. The book encourages creativity, problem-solving, and a sense of wonder about the world of electricity. Even today, the book’s emphasis on accessible learning and the joy of invention remains relevant and inspiring.