Originally Posted By: Greg Fretwell
This post was automatically imported from our archived forum.
Most people would never know if the outlets were wired backward, in fact polarized plugs and receptacles are really a fairly recent thing. If you look at 60s and even early 70’s appliances you will see both prongs of the plug are the same size.
If the appliance is double insulated it makes no difference and that is why some new things still have unpolarized plugs. Where this does make a difference is when one side of the power line is more likely to be touched than the other. The best example is a lamp. Properly wired lamps have the grounded conductor connected to the threaded shell of the socket so if you choke up on a bulb while you are screwing it in you will not touch the hot side. Back in the olden days TVs and radios might have one side of the chassis connected to one side of the line but, alas that was before polarized plugs were used. Perhaps that was the reasoning of polarized plugs but the transistor pretty much made “hot chassis” machines obsolete before polarized plugs were required.
Now virtually anything “electronic” uses a switch mode powersupply or it runs from a transformer. In either case both input leads will be isolated from the chassis, in fact they don’t even use a chassis anymore. It is just a card.