## 1. DC/AC(1 Phase and 3 Phase) Supply

DC Supply

DC is straight forward. In a DC power supply, the current flow only in one direction, between negative Cathode to positive Anode. When any load (like a resistor or an LED) is connected across a battery, the current flows through the load and the load uses the current flow. In case of a resistor heat energy is released. For an LED light is emitted.

Single Phase AC Supply

Flow of electric current in the wire generate Magnetic field around the wire and vice versa, current is generated in the wire when a magnetic field is introduced. When a magnet is moved in a coiled wire with multiple turns, a current is generated in the coil. Instead of using a permanent magnet, electromagnet can be used with varying magnetic field to generate more current.

When a magnet is rotated closer to a coil, at the point of strongest field a maximum current Is generated, the current gradually decreases to 0 and finally goes to minimum negative current. This cycle resembles a sine wave, and this cycle happens 60 times in a second (Frequency)~ 60Hz AC. It is 60Hz in the US and is 50Hz in Europe. It varies with what each country decides.

A coil can hold more electromagnetic field compared to a single wire. As the number of turns in the coil increases the electromagnetic field increases, this generate more current. This back and forth Alternating flow of current due to Electromagnetic field is called Alternating Current (AC).

This is how a single phase AC works.

Three Phase AC Supply

Just like Single Phase, Assume an Electromagnet at the center and if this time 2 more coils be placed with the initial coil at 120 degrees with respect to the first coil. It will be 3 phase AC supply.

Why 3 Phase? When 3 loads need power at the same time, instead of using 3 different sets of transmission cables, a 3 phase AC supply is used.

To close the circuit with three phases, a Neutral connection should be connected. But when all three loads are equal, the net current at the node will be “0”. So for a Balanced load condition, there is no Neutral Line.

To be continued…