Science fair project on lighting a LED?

I'm doing a science fair project on lighting a LED. It's simply a LED connected to a 9V battery. What would I write for a hypothesis and theory?

 

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Why ask us, you're the one with the class assignment so you have to do what you think you should.

 

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I think you need to try harder than a makeshift torch.

I also think you'll need more than just an LED and a battery. LEDs have a max V and A rating, you'll need to make sure you don't apply too much of either by using a resistor, so you could show how you calculate the resistance you need in your circuit using Ohm's law, that would at least put some science into your science project. Show the circuit, explain what each component does, and why the resistor is required.

 

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Thanks for your reply!
I get some useful information.

 

I would suggest that you first learn how to light an LED with a 9V battery without burning out the LED (as previously explained). Next, you may want to show how you can get more light from the same amount of power by stacking LEDs and using a smaller resistor.

Next, you could provide some explanation of why the LED can be more energy efficient than a standard tungsten filament bulb. This will lead to a discovery of how and where the LED makes a good replacement for other lighting sources.

These are just suggestions, you might have some other reasons of your own for wanting to demonstrate something about LEDs.

 

Thanks very much for your suggestions. I'll think about it carefully.

 

You may also want to be able to vary the level of illumination. The easiest way is to use a variable resistor, as pointed out above you want to have a minimum resistance in line to protect the LED from burning out, introducing potential dividers. You could look at other methods of varying the illumination (PWM, etc), are they more efficient than the simple divider - how long does it take to recover the extra costs?