A circuit is connected to an ac source of variable frequency. As the frequency of the source is increased, the current first increases and then decreases. Which of the following combinations of elements is likely to comprise the circuit?

A 15 $$\Omega$$ resistor, an 80 mH inductor and a capacitor of capacitance C are connected in series with a 50 Hz ac source. If the source voltage and current in the circuit are in phase, then the value of capacitance is

A 300 $$\Omega$$ resistor and a capacitor of $$\left( {{{25} \over \pi }} \right)$$ $$\mu$$F are connected in series to a 200 V $$-$$ 50 Hz ac source. The current in the circuit is -

The core of a transformer is laminated to reduce the effect of