Power Struggle
You may have noticed that the prongs on certain plug-ins are different sizes (one is sometimes larger than the other), while others have the same sized prongs. These are known in the US as polarized and non-polarized plug-ins.
This simple observation might not be that interesting or concerning at the moment. Why would it matter to you? Well, try to think back to the last time you tried plugging in a device with polarized prongs in a place that was hard to reach. It may have taken more than one attempt to make the connection because the plug could only be inserted one way. However, this doesn’t occur with all your devices: items such as chargers or Christmas lights can go in either way. This seems much easier, so why the difference?
Making the prongs on a polarized plug-in each a different size is important for items with switches. The different size prongs make it so that the “hot leg of the electrical circuit always contacts the hot terminal of the appliance you’re using… The hot leg is always on the same side of the device, and manufacturers place switches as close to the hot terminal as possible.” This is important because it prevents the device from becoming energized while the switch is off. Without it, the user could be shocked. Devices and appliances without switches do not run this risk and, as a result, do not need polarized prongs.
Knowing that polarized prongs function as a preventative, safety measure does make it easier to be less frustrated when one has to get down on their hands and knees to plug in that coffee-maker. However, this doesn’t mean that the act of plugging in devices could not be improved. If it were as optimal as it could be, users would not have to think about the act itself at all. It would all occur without expending a conscious effort. Addressing this requires taking a look at the design of the outlets being used since we now understand why the prongs need to be inserted in a fixed manner.
Let’s begin by considering the outlet shown below:
The issue with this outlet design is that it tells the user nothing about the way the plug-in blades should be inserted. Instead, a guess and check approach is taken. This means that in terms of a learnability approach the design is moderate. It is easy for the user to assume that the prongs should be inserted into the slits, but one has to guess the necessary orientation. A general score would also begin to decrease when considering memorability and efficiency. When looking at this outlet, the user does not intuitively recognize which way the plugin should go. The user could simply remember that the polarized prong requires that the wider blade touch the “neutral” portion of the outlet and the narrow prong in the “hot” portion of the outlet, which tends to be slightly wider. However, as outlet orientations change from location to location, even this would require a low-level consideration from the user.
Some solutions to this issue have appeared. For example below is an outlet from my own room. As you can see the neutral portion of the outlet has been indicated by the sideways T-shaped insert. Even this, however, does not clearly convey to the user which portion of a polarized plug should go where. Instead, they are simply able to recognize that there is an overall difference. Prior to this assignment, I gave no thought to what this design was illustrating to me. It simply seemed to be a random shape that I could ignore.
Another idea, that could be coupled with the T-shaped design could be different colored boxes around the insertion points that demonstrate a clear difference between the wider and narrower slots. Below I have provided a rough image of what that could look like.
Simple improvements such as this one could help make this interface more intuitive for users.
