jewel / joule are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
jewel: (noun) a precious or semiprecious stone incorporated into a piece of jewelry. (noun) a person who is as brilliant and precious as a piece of jewelry.
joule: (noun) a unit of electrical energy equal to the work done when a current of one ampere passes through a resistance of one ohm for one second. (noun) English physicist who established the mechanical theory of heat and discovered the first law of thermodynamics (1818-1889).
jewel: jh·UW·ah·l
joule: jh·UW·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)