Final answer:
The short leg of an LED in Tinkercad is the cathode, which is the negative side. This leg connects to the lower potential side of the power source, unlike the longer anode leg.
Step-by-step explanation:
On an LED in Tinkercad, the short leg is known as the cathode. The cathode is the negative side of the LED, and it should be connected to the lower potential side of the power source. The longer leg is the anode, which is the positive side, and connects to the higher potential, typically the positive voltage. It's important to connect the LED correctly to ensure it functions as intended without damage.