Geography of a Power Supply.

The power supply is the most important thing in a PC. Without a supply, all you have is a box of plastic and metal. Old power supplies were large, using bulky transformers and massive capacitors. They converted 120V to 5V like we still do today, but much less efficient. Now, power supplies are small and efficient with only one transformer doing the step-down from 220V to the specified amount.

Some of the main companies that produce power supplies are Corsair and EVGA. Both produce power supplies that are mostly of the same standard. Corsair produces a 1500i power supply, meaning, it can supply 1500 watts of continuous power. This is also fully modular which means that you can choose the cable that you want to plug into the supply. 

A power supply is made in much the same way a motherboard is, just with a big metal case around it. The case is usually made of aluminium. An aluminium sheet is cut out and the appropriate holes are cut out, such as a fan hole, a hole for the cable for the PSU itself, etc. The sheet is then folded to make a box. The board of the PSU is made by stacking two pieces of carbon-fibre over very thin copper wires. The capacitors and transformer has to be soldered on to the board by drilling a hole though it. After all the bigger components are soldered onto the board, the board is placed into the aluminium casing. It's secured with screws. 

http://www.corsair.com/~/media/corsair/product%20photos/psu/ax-series/ax1500i/large/ax1500i_psu_sideview.png