Introductionperforming even above 30 MHz are currently the object of research onelectromechanical effects found in piezoelectric and piezomagnetic materials.Primary sources of energy are often found in mechanical form in thekinetic energy of an expanding heated gas and in the potential energy ofwater at an elevation. Electromechanics has always played a vital role inobtaining large amounts of electric power from primary sources. This isaccomplished by using large magnetic field-type devices called rotatingmachines. Today a single generator can produce 1000 MW (at a retail priceof 2 cents/kWh this unit produces an income of $20,000/h), and as electricutility systems grow larger generating units (with attendant problems of anunprecedented nature) will be needed. This need is illustrated by the fact thatin 1960 the national peak load in the United States was 138,000 MW, whereasit is expected that in 1980 it will be 493,000 MW, an increase of more than250 per cent in 20 years.
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