Posted by admin on Dec 31, 2020 in Other subjects | 0 comments
1. PLASTIC MATERIALS
In general, plastic materials are a normal part of everyday life. They also play
important roles in sectors such packaging’, telecommunications, transport,
construction, medicine, agriculture and information technology.
Plastics consist of long chains of molecules, mostly made of the element
carbon.
1.1 THE ORIGIN OF PLASTICS
Plastics can be divided into two types, according to their origin:
Natural plastics are obtained directly from vegetable or animal sources.
For example,
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Posted by admin on Mar 13, 2020 in Other subjects | 0 comments
Excerpt. In 1819 a danish physicist. H. C. Ostered was carrying out an ordinary class demostration. He passed an electric current trough a copper wire wich was joined to a voltaic cell. Amongst the apparatuses on his demostration bench there happened to be a magnetic needle and Oersted noticed that when his hand holding the wire moved near the needle the latter was deflected. With a quick jump of imagination he desconnected the ends of the wwire and connected them to the oposite ends of the Read More
