Question

An electric lamp having coil of negligible inductance connected in series with a capacitor and an a.c. source is glowing with certain brightness, Fig. How does the brightness of the lamp change on reducing (i) capacitance (ii) frequency

Answer 1

Brightness of lamp `prop I_(v)^(2)`
Assumign zero resistance and zero inductance of lamp, `I_(v) = (E_(V))/(X_(C)) = (E_(V))/(1//omega C) = E_(v) (2 pi v) C`,
On reducing C or `v , I_(v)` would decrease. Therefore, brightness of the lamp will decrease.