I used NI multisim and created a circuit with a 555 timer that will allow a diode to flash at a frequency of about 4HZ. This is the circuit:
As you can see in the above image, the oscilloscope graph is a square wave constantly changing from high to low which means the light is flashing on and off. Nothing wrong with this.
After that, I tried to make a simple modification to the circuit by adding in an NMOS as a switch for the 10V DC source. In the image below, I am pretty sure that I set up the NMOS correctly. I'm feeding the gate of the NMOS a voltage of 0V. You'd expect the output of the oscilloscope to be a flat horizontal line at y=0 which means that no current/voltage is reaching the diode. However, this does not happen. I see the same square wave from before.
I hope the images are clear enough. I am unsure what I have done wrong. Any help would be greatly appreciated. Thank you!