I am not sure if your professor has some hidden reason behind option (C), but the correct answers are (A)
& (B) and here is why...
If your professor is referring to the distribution and transmission of power (either AC or DC) then yes, AC has less power loss. There is quite a bit of theory involved here but here goes:
- Due to the nature of AC, it can be very easily transformed from one voltage to another (compared to DC) because of the ever changing direction and amount of current flow. This constant change of direction and magnitude of current flow in an AC circuit creates a magnetic field around the conductor that also increases and decreases with the changing current flow. The magnetic field also changes polarity when the current changes its direction of flow. Transformers are AC devices and require this fluxuating magnetic field to induce a voltage and current into the secondary windings. DC does not change direction of flow and, all else equal, doesn't change the amount of current flow either. There is no such thing as a DC transformer because the magnetic field surrounding a conductor in a DC circuit doesn't have a fluxuating magnetic field.
- Because it can be transformed, a much larger voltage can be produced, and in turn a smaller amount of current is required, that is then used to transmit the same amount of
power over long distances. Power equals voltage x current (P=IxE). The equation for power loss in a conductor is I
2R (current squared x resistance of the conductor). Using this power loss equation, if the current was reduced by half then the power loss will actually be reduced by 3/4 of its original amount. Also, using the proper size conductor (the R or resistance of the circuit) affects the amount of power loss because it is the actual opposition to this current flow. A larger conductor will have less resistance - which 'uses' power and converts it into heat.
So I hope that helps...and I wouldn't want to taste
any AC or DC voltage because it hurts and can do bad things to you like burns and death
.