A lamb in which 10 A current can flow at 15 V is connected with an alternating source of potential 220 V and frequency 50 Hz. What should be the inductance of choke coll required to light the bulb?

Explanation

Resistance of the lamp, `R=15/10=1.5Omega`
To send 10 A current through the lamp. Required impedance of the ac circuit, `Z=220/10=22Omega`
Now if L be the inductance of the choke coil and its resistance is negligible, then
`Z=sqrt(R^2+(omegaL)^2)`or,`omegaL=sqrt(Z^2-R^2)`
`thereforeL=1/omegasqrt(Z^2-R^2),[omega=2pif=2times3.14times50=314 Hz`]
`=1/(314)sqrt((22)^2-(1.5)^2)=0.07H`