Question
Answer the following questions:
A choke coil in series with a lamp is connected to a dc line. The lamp is seen to shine brightly. Insertion of an iron core in the choke causes no change in the lamp's brightness. Predict the corresponding observations if the connection is to an a.c. line.
Solution
For a steady state d.c., L has no effect even if it is increased by inserting an iron core in the choke of the coil. For a.c., the lamp will shine dimly because of the additional impedance of the choke. It will dim further when the iron core is inserted because the choke's impedence is increased further.
