Tipul asta face niste demonstratii interesante in laborator! Imaginile sunt suficiente!
http://www.youtube.com/watch?v=9pdpygM5iK8&feature=related
http://www.youtube.com/watch?v=iUD2Wq8Tl7Y&feature=related
http://www.youtube.com/watch?v=YC56zXYa4W8&feature=related