The video: Scandalous!
I saw this video going around of engineering students at their graduation from MIT who were unable to power a light bulb using a battery and a single wire:
It is surprising that the engineers would have trouble rigging up the circuit. Let's take a look at the problem and see what this episode can teach us about effective learning.
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The solution: Back to the basics of electricity
A conventional lightbulb has two terminals—one at the base and another at the threads of the bulb. If these two terminals are kept at differing voltages, current will flow across the bulb, causing the filament to glow.
The obvious way to close the circuit and light the bulb is to use two wires:
- connect a wire between one terminal of the battery and the rim of the light bulb
- and a second wire between the other terminal of the battery and the base of the bulb.
While the setup with one wire appears to be different, it is actually the same. We can see this by drawing a diagram.
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Case 1: Closing the circuit with two wires
Consider the conventional circuit with two wires
Let’s ask ourselves a simple question: what is a wire? The answer is: a tool to connect two components of an electrical circuit. This is all the insight we need to close the circuit with one wire. \[ \] \[ \]
Case 2: Closing the circuit with one wire
Looking at the battery and the light bulb, it's clear that we can touch one of the terminals of the battery directly to the threads of the bulb.
For instance, by touching the positive terminal of the battery to the thread of the bulb, we put the threads at the same potential as the positive terminal. If we now use the wire to connect the terminal at the base of the bulb to the negative terminal of the battery, the circuit will close, with a sustained voltage across the terminals of the bulb that's equal to the voltage of the battery—let there be light!
Thus, we can eliminate one of the wires without incident.
You may have noticed this isn't the only way to close the circuit. In fact, there are three other arrangements that will work. While the bulb requires a voltage across its terminals, it doesn't care about the polarity.
So, we could also do the following:
The simple lesson is: if there's a way to make two circuit components touch without using a wire, we don't need to.
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A hazard of higher learning: Losing the basics
Those students probably all knew how lightbulbs, circuits, and batteries worked. However, they also probably spent the last several years of college in upper division classes that focused on abstraction and theory. When confronted with the basics, they no longer recognized where the lightbulb and the battery fit into their skill set and knowledge base. This is not a problem unique to MIT or elite academia. Losing track of the basics is an innate hazard of learning a lot very quickly.
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Conclusion: Develop a firm understanding of simple cases
In any field that you find yourself in, you can protect yourself from a future light bulb + battery moment by laying your foundational knowledge in the firm understanding of simple cases. If you have a sound understanding of the fundamentals in your discipline, you will always be able to derive more sophisticated ideas from the basics. Conversely, it's extremely hard to rediscover the fundamentals from merely remembering the wealth of fancy results of your field of study. In other words, when you get lost… go back to the basics.
Want more like this? Check out the Physics of the Everyday course.