Which best compares ac and dc?
ac flows in one direction, and dc repeatedly switches direction.
dc flows in one direction, and ac repeatedly switches direction.
ac is used only in generators, and dc is used only in motors.
dc is used only in generators, and ac is used only in motors.

List four observations that indicate that a chemical reaction may be taking place

The scheme below is from a series of reactions that are part of a synthesis of vitamin a. answer the following questions with reference to this scheme. (i) what is "reagent a"? (ii) draw a step-by-step mechanism which explains the formation of compound c from compound b (iii) which reagents would you use to form compound e from compounds c and d (reagents b and c)? for each reagent suggested above in (ii) explain the role of the reagent in the reaction to (iv) form compound e. you may wish to do this by drawing a mechanism. 1. addition of reagent a но reagent a 2. н,о" thо oh нон-с compound a. compound b. compound c .ch-оh 1. reagent b "сно 2. reagent c сh oh compound e. compound d.

Joan writes four numbers on the board in standard form, and then she writes their scientific notation