# The Light Bulb Test

Thomas Edison was an inventor famous for several types of major technologies, including the first commercially viable incandescent light bulb. One story you may be less familiar with, however, is that of the Edison Light Bulb Test.

The story goesâ€¦

When Edison interviewed new engineering applicants he asked them all the same question. â€śCan you determine the exact volume inside this light bulb?â€ť Like most problems, Edison knew there were two basic ways someone could approach this problem:

Identify all complex angles on a light bulb using tools such as engineering gauges and math protractors. After, using a slide rule and logarithmic equations, one could calculate the area inside of the light bulb.

Take the base off the bulb, fill it with water, and measure the volume of water it takes in a graduated cylinder.

The first option would take an experienced engineer about twenty minutes. The second would take less than two minutes.

Edison would politely thank those who used the first approach and send them on their way. Those that used the second, however, were quickly welcomed and asked, â€śWhen can you start?â€ť

We love how this story points out that there are many ways to approach a problem. Sometimes the simplest way is not always the easiest to see. At Waterclock Engineering, we strive to help you find these solutions in the most efficient way. That said, we do have the engineering expertise to back it up. For fun, in fact, we thought weâ€™d derive the general equation for the volume of a light bulb ourselves. See below:

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