Questions

Saturn, the solar system's second largest planet that takes the prize for least dense. It's less dense than water, which has led many people to postulate that it would float.

However, even if it somehow found its way to a body of water large and deep enough to contain it, Saturn would break apart and its rocky core would sink.

A device which is used to convert light energy directly into electrical energy is called as photovoltaic cell or a solar cell.

Heliostats convert light energy into heat energy.

A thermocouple is a device for measuring temperature.

United State Library of Congress, Washington D.C.

The American noncommissioned officer tradition began with creation of the Continental Army in 1775 at the beginning of the American Revolution. They adopted NCO traditions from French NCO.

The Chinese writers mention India by the name of "Yin-tu".

It is ABACUS.

Words formed are as below 

BUS
CAB
CUB
US