The resistor '$R$' inductance '$L$' and capacitance '$C$' are connected in series with an a.c. source. When 'L' is removed from the circuit, the phase difference between voltage and current in the circuit is $\dfrac{\pi}{3}$. If instead, C is removed from the circuit, the phase difference is again $\dfrac{\pi}{3}$. The power factor of the circuit is

The LC series resonant circuit produces a resonant frequency '$f$'. If L is tripled and 'C' is increased by 3C, the resonant frequency will be

In LCR series circuit at resonance

A transformer has 120 turns in the primary coil and carries 5A current. Input power is one kilowatt. To have 560 V output, the number of turns in secondary coil will be