|OddMix TECHNOLOGY - PHYSICS|
Resistor the Most Often Used Electronic Component Home Made Grid Leak
|Figure 1. Carbon Compound Resistors 2, 1, 1/4 and 1/8 Watts Size|
The most often used component in electronics is without a doubt the resistor. Resistors are conductive components made to resist the flow of the current to some specific degree. By physical appearance there are two major resistor groupings possible - fixed and variable. Many different types of resistors are made and used for a wide variety of purposes. Major groups of resistors by construction are the wire is the oldest form. The solid - usually carbon-composition types - Figure 1, are made and used mostly in the US and deposited film of metal or carbon used all over the world.
Early electrostatics experiments demonstrated that substances could be classified as conductors and non-conductors. Resistance is a property of conductors that impedes the flow of current in the substance. The resistance of a wire depends on the type of the metal: its length, and its cross-section. Every primary conductor and non-conductor (solids) and secondary conductor (electrolytes) has some resistance.
|Figure 2. Home Made Grid Leak Resitor Assembly Cross Section|
George S. Ohm (1789-1854) was the son of a German locksmith, who later was appointed a professor of physics in Munich in 1849. Professor Ohm conducted the original experiments in 1826 by which he demonstrated the relationship between current, resistance and voltage. That relationship is named after him as Ohm's Law. Ohm's Law stated that in any wire of uniform temperature, the current flow is directly proportional to the potential difference between its ends. In mathematical terms the E/I is a constant ratio. The numerical magnitude of the ratio E/I is a measure of the resistance of a conductor.
Early radio and any electrical, electronics circuits required some resistors. Initially, the radio amateurs made resistors themselves, but soon an entirely new industry was built for the manufacture of electronic components. Grid leak resistors usually have high values, typically a few megohms. Making a resistor like that is not hard - Figure 2. A pencil line made on a strip of paper with a soft pencil is all that is required. A simple measurement with an Ohmmeter indicates the resistance of the line and if any further action is necessary. Wider lines or one made with softer pencil lowers the resistor's value. Once the line is satisfactory, the paper strip is placed inside a glass tube to protect it mechanically. Flattened end copper wires in contact with the pencil line on the paper provide the contacts.