The DC motor was the mainstay of electric traction drives on both electric and diesel-electric locomotives, street-cars/trams and diesel electric drilling rigs for many years. The introduction of DC motors and an electrical grid system to run machinery starting in the 1870s started a new second Industrial Revolution.
One acre is 43,560 sq ft. One half acre is 21,780 sq ft. However, that doesn't help most people much when trying to picture how large a lot is. Half acre lot is roughly:
Five years ago, the average single-family home typically would be 2,000 square feet on a quarter-acre, according to Robinson. Today, it is probably 3,000 square feet, Robinson said. Ryland already has taken into account consumers' preference for a big-box design. The area's No. 2 builder is introducing a line of homes in Bel Air in Harford County that go up to 3,800 square feet, sell in the $260,000 range -- modest for its size -- and are situated on a quarter-acre. What they really are is just great big boxes ... just great big houses, Robinson said.