Four identical electrical lamps are labelled `1.5 V` `0.5 A` which describes the condition necessary for them to operate at normal brightness. A `12 V` battery of negligible internal resistance is connected to lamps as shon, then

Options

A. The value of R for normal brightness of each lamp is `(3//4) Omega`
B. The value of R for normal brightness of each lamp is `(21//4) Omega`
C. Total power dissipated in circuit when all lamps are normally bright is 24 W
D. Power dissipated in R is 21W when all lamps are normally bright

Answer

B, D

Explanation

Main current I =2A
Voltage = 1.5 V
Now, `V_(R) = 12-1.5=10.5 V`
Power dissipated `=(10.5)^(2)/(21.4) = 21 W`