Read the passage. AC vs. DC
In the 1880s, the War of the Currents began. Thomas Edison developed direct current, or DC, a type of electricity that flows in one direction. By 1887, DC was in use around the United States. It had some drawbacks, though. Converting it to lower or higher voltages was difficult; that is, the current's force couldn't be changed easily. Transmitted at the low voltage needed for use in homes and businesses, it lost power after traveling only a mile. Meanwhile, Nikola Tesla was working with alternating current, or AC. AC reverses direction many times per second and can be changed to different voltages. At high voltage, it can be transmitted efficiently, traveling hundreds of miles with little energy loss. Because of its advantages, AC triumphed by the end of the nineteenth century.

What is the main idea of the passage?

AC has distinct advantages over DC, so AC won the War of the Currents.

AC reverses direction and can be converted to lower or higher voltage.

What is the main idea?

What type of writing is demonstrated in this excerpt by general philip henry sheridan? at once i set about preparing for the examination which precedes admission to the military academy, studying zealously under the direction of mr. william clark; my old teachers, mcnanly and thorn, having disappeared from somerset and sought new fields of usefulness. the intervening months passed rapidly away, and i fear that i did not make much progress, yet i thought i should be able to pass the preliminary examination. that which was to follow worried me more and gave me many sleepless nights; but these would have been less in number, i fully believe, had it not been for one specification of my, outfit which the circular that accompanied my appointment demanded. this requirement was a pair of "monroe shoes." now, out in ohio, what "monroe shoes" were was a mystery—not a shoemaker in my section having so much as an inkling of the construction of the perplexing things, until finally my eldest brother brought an idea of them from baltimore, when it was found that they were a familiar pattern under another name. a. research essay b. persuasive essay c. biography d. memoir