turn on LED with transistor

[OutoftheBOTS]

Ok I have made a little circuit to turn on and off a LED with the RPi using a PN100 transistor as it was the one that I could get down the road near my house easily.

I have a 100ohm resistor to limit the current to the LED and a 4.7k ohm resistor on the base of the transistor to limit then current from the RPi GPIO pin

Now to my surprise when the GPIO pin connected the base is set to high the LED turns off and when the GPIO pin is set to low the LED turns on. I was expecting it to work the other way around

see my pic

[Heater]

Presumably you have wired it up incorrectly. Assuming all your components work as advertised.