secondary index is a key which is created other than primary key, to speed up processing.
occupation that involves manufacturing of finished products from raw materials are called secondary occupations
Machinery is considered a secondary product because it is manufactured from primary products, such as raw materials like metal and plastic. Secondary products are created through processing and assembly, transforming these raw materials into finished goods that can be used in various industries. In contrast, primary products are extracted or harvested directly from nature without significant processing.
Oil is considered a primary product as it is extracted directly from natural resources such as crude oil reserves. Secondary products are derived from primary products through further processing or manufacturing. Oil can be refined into secondary products like gasoline, diesel, and jet fuel.
Input, processing, output.
Secondary manufacturing refers to further processing of products that have already undergone some manufacturing. E.g. processing wood past its primary stage (e.g., lumber). Primary manufacturing is thus manufacturing of raw materials or materials in their near-natural state (e.g., iron ore, wood logs, ...)
Primary products are raw materials extracted from nature, such as minerals, crops, and livestock. Secondary products are manufactured goods produced by processing or combining primary products, such as processed foods, textiles, and automobiles. Primary products are the starting point in the production chain, while secondary products are created from these raw materials.
Plastic is considered a primary product, as it is derived from raw materials such as oil or natural gas through a manufacturing process. Secondary products refer to items that are made from primary products through further processing or refinement.
The primary sector relates to the extraction and production of natural resources - like farming and mining. The secondary sector relates to the processing of the resources, which includes manufacturing. The tertiary sector relates to the support of the primary and secondary sectors. This includes transportation, banking, insurance, etc.
Primary Means, it is individual there is no dependence, But Secondary will allays depends on Primary, If you want to do Secondary, you should complete primary first, There is no precondition to primary, but for Secondary Primary is the Precondition, first you should do primary, then only you are able to do secondary.
primary and secondary demand
Voltage on primary/Primary turns = Voltage on secondary/Secondary turns