Why is power transmitted for long distances in the form of a.c. not in the form of dc? The one who gives the best answer will be marked as branalist..
Answers
because of low power losses when transmitted through ac not in form of dc
It is more efficient to transmit DC using about the same infrastructure. This is because of several effects:
Skin effect experienced with AC. There is no skin effect with DC.
Higher voltage allowed with DC for the same transmission lines. The lines have to withstand the peak voltage. With AC, that is 1.4 times higher than the RMS. With DC, the RMS and peak voltages are the same. However, the power transmitted is the current times the RMS, not peak, voltage.
No radiation loss with DC. Long transmission lines act as antennas and do radiate some power. That can only happen with AC.
No induction losses. The changing magnetic field around a wire carrying AC current causes induced voltage and current in nearby conductors. In effect, the transmission line is the primary of a transformer, and conductors near it are secondaries. With DC current, the magnetic field doesn't change and therefore doesn't transfer power.
Another advantage of DC is that it doesn't require synchronization between grids. Two AC grids need to be phase-synced to be connected together. This gets tricky when the distances are large enough to be significant fractions of a cycle.
The flip side is that AC is easier to convert between voltages. Converting DC back to AC to dump it onto the local grid at the receiving end is not a trivial process. It takes a large plant to do this, which means significant expense. That expense is only worth it if the transmission distance is long enough so that the efficiency savings outweigh the cost of the DC-AC conversion plant over its lifetime.