Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:
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 12V battery of negligible internal resistance is connected to lamps as shown then (1) the value of R for normal brightness of each lamp is\[(3/4)\Omega \] (2) the value of R for normal brightness of each lamp is \[(21/4)\Omega \] (3) total power dissipated in circuit when all lamps are normally bright is 24 W. (4) power dissipated in R is 21 W when all lamps are normally brightA) 1, 2 and 3 are correct
B) 1 and 2 are correct
C) 2 and 4 are correct
D) 1 and 3 are correct
Correct Answer: C
Solution :
For normal brightness of each bulb see following circuit. Current through each bulub\[=0.5A\] So, main current\[i=2\text{ }A\] Also, voltage across the combination\[=1.5\text{ }V\] So, voltage across the resistance \[=10.5\text{ }V\] Hence, for resistance\[V=iR\] \[\Rightarrow \] \[10.5=2\times R\] \[\Rightarrow \] \[R=\frac{21}{4}\Omega \] Power dissipated in\[R=\frac{{{(10.5)}^{2}}}{21/4}=21\,W\].You need to login to perform this action.
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