Dimensional Analysis. Dimensional Analysis (also called Factor-Label Method or the Unit Factor Method) is a problem-solving method that uses the fact that any number or expression can be multiplied by one without changing its value. It is a useful technique.
In 1887, the first dry cell battery was invented. Unlike previous batteries, it used a paste electrolyte instead of a liquid.
Gel battery. Originally a kind of Gel Cell was produced in the early 1930s for portable Valve (tube) radio LT supply (2, 4 or 6V) by adding silica to the sulfuric acid. By this time the glass case was being replaced by celluloid and later in 1930s other plastics.