Which is an advantage of ac over dc power?

a. ac voltage can be transformed into other voltages through transformers.

b. ac voltage is more easily used in the home.

c. ac circuits are safer.

d. it's easier to produce ac voltage with a portable, chemical battery.

its a

The correct choice is

A. AC voltage can be transformed into other voltages through transformers.

Explanation:

We can convert an AC Voltage to other higher or lower voltage making use of a step up or step down transformer. Electricity is transferred over long distances at high voltages as the losses are minimum at high voltage. The electricity can not be used in households at such high voltage. So the high voltage is converted to low voltage using transformers. This can only be done in case of AC Power.

less than one you can't create energy

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.