A
why do we see different phases of the lunar cycle?
as the moon rotates around its axis, different sides of it become visible.
as earth rotates around its axis, people can see different sides of the moon.
as earth revolves around the sun, the moon is cast in different shadows by earth.
as the moon revolves around earth, the different amounts of the sunlit side faces earth.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current

може ли да зареждате повече информация, моля