(a) A series combination of L, C and R is connected to an a.c. source. Using a phasor diagram, derive an expression for the impedance of the circuit and phase difference between V and I. (b) Under what conditions the (i) impedance of the circuit is minimum ? (ii) Wattless current flows in the circuit ? OR (i) With the help of a labelled diagram, explain the principle, construction and working of an a.c. generator. (ii) Deduce an expression for the induced emf in the coil of the generator. (iii) If T is the time period of the rotation of the coil, at what values of T in a cycle, the emf generator is maximum ?