Which of the following is an accurate statement? a. dc generators produce current with a voltage that changes from positive to negative. b. step-down voltage transformers have a different number of turns in the primary than in the secondary winding, so they change the incoming voltage to a higher voltage. c. step-up voltage transformers have a lower number of turns in the primary than in the secondary winding. d. ac generators produce current that is pulsating, but always remains positive.

B. Step-down voltage transformers have a different number of turns in the primary than in the secondary winding, so they change the incoming voltage to a higher voltage.

d eras and periods

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day