Two similar bulbs of rating ( 100 W , 50 2 V ) are connected in circuit as shown. When frequency of source is varied, brightness of B 2 changes. It is observed that at 50 Hz frequency both the bul

Question

Two similar bulbs of rating ( 100 W , 50 2 ​ V ) are connected in circuit as shown. When frequency of source is varied, brightness of B 2 ​ changes. It is observed that at 50 Hz frequency both the bulbs have same brightness. Select correct alternative/s.

TestHub · Accepted Answer

At 50 Hz both bulbs are equally bright: $I_{1} = I_{2}$ , so $X_{L} = X_{C}$ and currents are in phase (A)

$R = \frac{V ^{2}}{P} = \frac{( 50 2 ) ^{2}}{100} = 50 Ω$ , $I_{1} = I_{2} = \frac{50 2}{50} = 2 A$ , so source current = $22 A$ (C)

The LCR branch is purely resistive only at 50 Hz, so B1 is brighter at every other frequency (D)

Answers (A, C, D)

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