1) AC and DC:
a) If have a DC circuit must use current limiting resistors on all loads that are dc so will not blow the dc parts up.
b) If an AC circuit you do not need to worry about current limiting resistors cause motors and coils, and transformers that use AC only consume what current they need when run and do not blow up unless there is a short then the current goes straight to ground and fries the motor or coil.
c) In DC and AC circuits use P=IV to make sure have enough power to support all loads. So why in part (a) and (b) for DC need to worry about current limiting resistors and for AC do not? Ohms law is ohms law. I see DC is a flat line and AC is a ripple,close to a line like 3 phase, but still ripple.