20. which of the following is an accurate statement?
a. dc generators produce current with a voltage that changes from positive to negative
b. ac generators produce current that's pulsating but always remains positive,
c. step-up voltage transformers have fewer turns in the primary than in the secondary winding.
d. 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

A transformer consists of two loops of wire with an AC current going through the "primary" loop inducing a voltage, and therefore a current, in the "secondary" loop.

The ratio of the induced voltage in the secondary loop to the voltage in the primary loop is equal to the ratio of the number of turns in the secondary loop to the number of turns in the primary loop.

A step-up transformer is designed to make the induced voltage in the secondary loop greater than the voltage in the primary loop. This requires the primary loop to have fewer turns than the secondary loop.

Choice C

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2