Definition: Resistors belongs to electronic components. They have a specific, never-changing electrical resistance. The resistor’s resistance limits the flow of electrons through a circuit. They are passive components, meaning they only consume power but can not generate power. Resistors are usually added to circuits where they complement active components like op-amps, micro controllers, and other integrated circuits. There are many things in our daily life can function as resistors, for example, pencils, and even our human body can be a resistor. Resistors have various shapes and sizes. They might be through-hole or surface-mount. They might be a standard, static resistor, a pack of resistors, or a special variable resistor.
Purpose: Limiting current, reducing voltage, or controlling other key characteristics of circuit performance. For example, a resistor can be used to limit the current travelling through an LED so that the LED is not damaged during operation.
Harm: Are they hazardous? You know what I am going to say. I would not ask if they are not dangerous. Lead that present in the solder may cause neurological damage and cancer if ingested or inhaled. These risks can be avoided by buying only ROHS compliant resistors. The compliant do not contain Lead. And some ceramic fillers may contain alumina whose dust may cause lung disorders. This risk can be avoided by keeping away from shredding resistors.
Recycle: The connecting wires of resistors are made of tinned copper plated steel, which can be recycled. It would be better if the body of the resistors not been thrown into landfill. Because resistors can be re-used over and over again if disassembled from printed circuit boards and other electronic assemblies, and they rarely fail.
Excess Inventory: If the resistors are kept in stock too long, the lead foot may be oxidized, which would lead to the failure of soldering. So they must be tested before they are being used if the products are kept for more than 3 years.
Manufacturers: At present, the global resistance market has formed a competitive situation in which “ Taiwan focus on quantity and Japan focus on profits”. Japanese manufacturers like ROHM, KOA and Panasonic focus on the high-end market. They are not dominant in terms of the quantity of shipments, but sales account for a large share; Taiwanese manufacturers "win by volume", accounting for nearly 70% of the world capacity.
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