Advantages and disadvantages of DC source?

This was a fight between Edison (DC) and Steinmetz, Tesla and others (AC).
The big advantage of AC: it is easy to change the voltage using transformers. AC in the US may go over high power lines at hundreds of thousands of volts; be distributed in town at 13,000 volts and to houses at 220 volts (split to 110 volts either side of neutral).
DC power is usually needed inside most electronic devices, so it must be rectified (changed to pulsating DC) and smoothed.

Since the advent of solid-state devices, it is now as practical to distribute DC as AC, stepping the voltage up or down electronically as needed. The 110 VAC input to a compact fluorescent lamp is rectified to about 150 VDC (110 volts is the RMS level, a bit of an average, the peak is 1.414... times that). The 150 VDC is transformed to 10,000 - 500,000 Hz AC (vibrating 10,000 to 500,000 times a second) at a few hundred volts to start the lamp and drops back to about 10-20 volts once a steady discharge occurs.
One I remember. AC contracts muscle, so you would grab a live bar. DC throws you away. If you must check, use Back of hand

line loss is less, i^2*r. for ac i^2*z

easy to reverse the motor like the subway train, just by reversing the polarity of the source.

disavantages :

cannot use transformer to transmit the power in high voltage (lower current to cut down the line loss). that is why the power distribution now is using ac

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