Ohm's Law & circuits

Ohm's law is a formula that establishes the relationship between voltage current and resistance. The formula is Voltage (V) = current (I) x resistance (R). If you want to know the current for example than the formula would be V : R = I. This is the same for resistance except you have to divide the voltage with the current.

Ohm's law pyramid illustrated by Andrei Motian

Circuits with LED's and resistance

In this assignment i want to light a LED on paper by using some copper tape, resistance and a 3 Volt battery.

The paper had the whole circuit printed on it that made it easier. Picture: Andrei Motian

It is important to know from the LED that the long pin is + and the short - and to connect it the right way otherwise it wont light up.

I started first to stick the copper tape where needed from + to -.

Then i sticked the resistance on the right place with some copper tape on top of each pins. Here it is important to put the pins on top of the copper tape that are on the paper and on top of the pins some new copper tape so its stuck. The sticky side from the copper tape is not conductive.

Then i sticked the LED pins in the copper tape the same way as i did for the resistance. Making sure that the + and the - where on the right side.

And now i've used the 3V battery and put it with the + side on top in the circle with the -. I folded the corner from the paper so the piece of copper tape inside the cirle with the + will touch the + side of the battery.

If done right the LED will light up. Picture: Andrei Motian

Now i want to measure some data with the multimeter, it is the first time i use one.

First thing i want to measure is the voltage of the battery. I allready know it is 3V because of the package but i want to see it for my own curiosity.

Measuring the battery. Picture: Summer Danoe

Now i want to measure the resistance. There were a few resistances i could choose but i didn't know wich one i had and how many ohm's it has. After measuring i discovered i had a resistance from 47 ohm.

Measuring resistance. Photo: Summer Danoe

Next thing i want to know is how many volts is going through the LED. That was somewhere around 2.8V

Measuring the voltage through the LED. Photo: Summer Danoe

And after measuring how many voltage is going through the resistance i had to add it up to the voltage from the LED and that will be the same amount as the voltage from the battery.

Here I have added it up. Photo: Andrei Motian

The battery gives 3V from the + side, the resistance uses 0,2V and the LED uses 2,8 and 0V is going to the -. If i did not use any resistance there would be 0,2V returned to the battery and it could get really hot.

By pressing on the velostat there will be less resistance. - Andrei Motian

Connecting a second LED. - Andrei Motian