A 20 volts 5 watt lamp (amp to be treated as a resistor) is used on AC mains of 200 volts and `(50)/(pi)sqrt11 c.p.s`. Calculate the (i) capacitance of the capacitor, or inductance of the inductor, to be put in series to run the lamp. (i) How much pure resistance should be included in place of the above device so that the lamp can run on its rated voltage. (ii) which is more economical (the capacitor, the inductor or the resistor).

Answer

`(i) (125)/(33)muF or 2.4H` (ii) `720Omega`
(iii) It will be more economical to use inductance or capacitance in series with the lamp to run it as it consumes no power while there would be dissipitation of power when resistance is inserted in series with the lamp,