Experiment 3 : Paths for the Flow of Electricity

This experiment lets us meet the LED and how it works.
In our kit, we see that the upper connection is the 4.5V and the lower connection is the grounding.
So, when we use blocks with nothing else then wires inside, we see that the current flows from the ground through all the blocks till it reaches the LED.
Inside this LED cube there is a resistor of 330 Ohms which protects the LED from burning.

With the law of Ohm, which states : U = R x I, we can calculate how much current flows through the LED.
U = Voltage
R = Resistance
I = Current

In our circuit, we know that the Voltage across the red LED is about 1.8V to 2V ( depending of the type of LED ). Let us assume the max. value of 2V
So, when we use the formula of Ohm, we can calculate the current through the resistor of 330 Ohms ( which is the same current through the LED )
4.5V - 2V = 2.5V
2.5V / 330 Ohm = 0.0076A = 7.6mA
This is a safe value for our LED