In an AC circuit, magnetic reversal due to phase difference between current and voltage occurs 50 or 60 times per second. A capacitor helps to improve the power factor by relieving the supply line of the reactive power.

The concentration of salt in seawater (its salinity) is about 35 parts per thousand; in other words, about 3.5% of the weight of seawater comes from the dissolved salts.

A flexible tube called an endoscope is used to view different parts of the digestive tract. When passed through the mouth (as shown on the left), an endoscope can be used to examine the esophagus, stomach, and some of the small intestine.

The earliest evidence of domestication of animals comes from Adamgarh (M.P.) and Bagor in Rajasthan dated 5500 B.C. and 4500 B.C. respectively.