Plate 8A Quartz Watch	8B Concrete Slab

(Source:http://www.google.co.in/search?num=10&hl=en&site=imghp&tbm=isch&source=hp&biw=
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w.r_qf.&fp=940f65a189f63371&biw=1341&bih=581 ; Aug. 31, 2012
8B:http://www.google.co.in/search?num=10&hl=en&site=imghp&tbm=isch&source=hp&biw=
1341&bih=581&q=expansion+%26+contraction+of+quartiz&oq=expansion+%26+contraction
+of+quartiz&gs_l=img.12...74285.93500.1.95672.15.2.0.13.0.0.693.814.0j1j51.2.0...0.0...1ac
.2eMJEvsJbis#num=10&hl=en&site=imghp&tbm=isch&sa=X&ei=FfFAUIzCJ4b3rQf1qYCoBw
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.r_pw.r_qf.&fp=7ee0a650f1619acf&biw=1341&bih=581 ; Aug 31, 2012 

Quartz and certain crystals expand and contract when an electric field is applied and released or reversed. Modern watches (plate 8A) have widely used the quartz for the accuracy and light weight. The bellow-joint is expandable and can contract. Similarly bellow-joints (discussed earlier) demonstrate the expansion and contraction characteristics.

Plate 9A Overhead Cover	9B Joining coaches	9C Bellow joining two coaches