Q. Explain workinf of colpitts oscillator?

When the collector supply voltage V cc is switched on, the capacitors C1 and Cz are charged. These capacitors C1 and Cz discharge through the coil L, setting up oscillations of frequency. The oscillations across capacitor Cz are applied to the base-emitter junction and appear in the amplified form in the collector circuit. Of course, the amplified output in the collector circuit is of the same frequency as that of the oscillatory circuit. This amplified output in the collector circuit is supplied to the tank circuit in order to meet the losses. Thus the tank circuit is g:etting continuously energy from the circuit to make up for the losses occurring in it and, therefore, ensures undamped oscillations. The energy supplied to the tank circuit is of correct phase and gain exceeds unity, oscillations are sustained in the circuit.