In a series $$RLC$$ circuit $$R = 2\,k\Omega ,\,\,\,L = \,1H$$ and $$C = \,1/400\,\mu F.$$ The resonant frequency is

For the circuit in figure, the phase current $${{\rm I}_1}$$ is

The ABCD parameters of an ideal n:1 transformer shown in Fig. are $$\left[ {\matrix{ n & 0 \cr 0 & X \cr } } \right]$$. The value of X will be

The h parameters of the circuit shown in Fig. are