What metal makes a great flashlight?   

Well it depends on your criteria. Let's talk about requirements for a flashlight first:
1) Electrical conductivity 
2) Thermal conductivity (the ability to absorb and radiate heat) 
3) Durability 
4) Cosmetics 
5) Cost 
6) Ease of manufacturing 
We'll talk about electrical conductivity today. 


So obviously, seeing as a flashlight uses electricity to operate, an extremely important property is the conductivity of the metal. 


I'll give you a quick simple overview of how a flashlight works just in case you don't know. 


The battery goes into a metal tube. Positive side towards the driver (electronics), negative side towards the switch (in a light with a mechanical switch). The light uses the body of the light as a ground to complete the circuit.   


Click the switch and electricity flows through the body to the emitter (LED bulb), and the light comes on.   


The conductivity of the metal has a direct effect on how well the light works. Metals with good conductivity will be brighter than metals with poor conductivity.   


So where does copper land in the conductivity world? 


Well, copper is the benchmark that other metals are measured against for conductivity.  Silver is better, but is really expensive and doesn't have great strength.  Aluminum has slightly less conductivity, great strength and is lightweight. It's a great material for lights. 


Why are we talking about aluminum now?   


It's a close race between aluminum and cooper for the perfect material to make a flashlight. Aluminum is by far the most popular material for making flashlights. 


So who wins the conductivity test? Copper of course. If copper's conductivity is 1, then aluminum's conductivity is 0.63.   


But there's other factors that make a great flashlight.

If you disagree or I've gotten a fact wrong, by all means, let me know in the comments.