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

Assertion (A) : A step-up transformer cannot be used as a step-down transformer.

Reason (R) : A transformer works only in one direction.