<P> The supply transformer (T) secondary winding is connected across the primary tuned circuit . It might seem that the transformer would be a leakage path for the RF current, damping the oscillations . However its large inductance gives it a very high impedance at the resonant frequency, so it acts as an open circuit to the oscillating current . If the supply transformer has inadequate leakage inductance, radio frequency chokes are placed in its secondary leads to block the RF current . </P> <P> To produce the largest output voltage, the primary and secondary tuned circuits are adjusted to resonance with each other . Since the secondary circuit is usually not adjustable, this is generally done by an adjustable tap on L 1 (\ displaystyle L1 \,) the primary coil . If the two coils were separate, the resonant frequencies of the primary and secondary circuits, f 1 (\ displaystyle f_ (1)) and f 2 (\ displaystyle f_ (2)), would be determined by the inductance and capacitance in each circuit </P> <Dl> <Dd> f 1 = 1 2 π 1 L 1 C 1 f 2 = 1 2 π 1 L 2 C 2 (\ displaystyle f_ (1) = (1 \ over 2 \ pi) (\ sqrt (1 \ over L_ (1) C_ (1))) \ qquad \ qquad f_ (2) = (1 \ over 2 \ pi) (\ sqrt (1 \ over L_ (2) C_ (2))) \,) </Dd> </Dl> <Dd> f 1 = 1 2 π 1 L 1 C 1 f 2 = 1 2 π 1 L 2 C 2 (\ displaystyle f_ (1) = (1 \ over 2 \ pi) (\ sqrt (1 \ over L_ (1) C_ (1))) \ qquad \ qquad f_ (2) = (1 \ over 2 \ pi) (\ sqrt (1 \ over L_ (2) C_ (2))) \,) </Dd>

What do you do with a tesla coil