questions about lc tank oscillator circuit

[Benhe]

first take a look at the image:

on the above image, the left hand side one. If output isn't connected to anything, would it still able to produce sine wave??

 

[Yoa01]

Technically no, but the only way to measure it would be to connect something to the output and ground (like a jack), thus completing the circuit and giving you a sine wave output. Most circuits tend to not work when there is no output as the circuit is not complete.

For example, by itself it does nothing because the circuit is not complete (there is no load resistance from output to ground). However, if you connect something, say a speaker or oscilloscope, to the output and ground, you would complete the circuit by introducing a load resistance, giving the circuit something to do.