Getting an IV characteristic for a red LED

 We used a potential divider to change the potential difference across a red LED. We measured the current through it for each voltage. To obtain negative voltages, we swapped the connections round on the power supply.

The graph looks like this:

There is no light for negative voltages but even with positive voltages, nothing happens until around 0.7V and even then we were getting current of 0.02A with 1.5V.