What is a transformer?

An ebook about Electrical Engineering topic " TRANSFORMER" contains many articles and definitons such as;

• A transformer is a stationary electric machine which transfers electrical energy (power) from one voltage level to another voltage level.
• Unlike in rotating machines, there is no electrical to mechanical energy conversion.
• A transformer is a static device and all currents and voltages are AC.
• The transfer of energy takes place through the magnetic field.
• It has 2 electric circuits called primary and secondary.
• A magnetic circuit provides the link between primary and secondary...............

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