Hi,
can anyone explain to me how the BJT make the circuit vibrate?
what every component does ? R ,C's, BJt.

And how can i analyze the circuit from the moment i connect the battery and the circuit start to work ?

thanks.

 

It's an Hartley Oscillator circuit.

 

It is one of the classical LC-oscillator circuits (Hartley).
The working principle is as follows: The negative feedback path comprises a third-order highpass which - at a certain frequency - produces a feedback voltage with 180deg phase shift. Because of inverting amplification, the loop gain has zero phase shift at this frequency - and the phase condition of the Barkhausen oscillation criterion is fulfilled.
The 3rd-order highpass is of the r-L2-C3-L1 type (r is the output resistance of the transistor).

 

It is one of the classical LC-oscillator circuits (Hartley).
The working principle is as follows: The negative feedback path comprises a third-order highpass which - at a certain frequency - produces a feedback voltage with 180deg phase shift. Because of inverting amplification, the loop gain has zero phase shift at this frequency - and the phase condition of the Barkhausen oscillation criterion is fulfilled.
The 3rd-order highpass is of the r-L2-C3-L1 type (r is the output resistance of the transistor).

OK. and what the use of C1 C2 R1?

 

OK. and what the use of C1 C2 R1?

Because the supply voltage is used as signal ground, the capacitor C1 provides a AC short to ground.
R1 provides the necessary DC bias for the transistor and C2 closes the feedback loop..