Current Electricity Charging Discharging Of Capacitors Question 98
Question: Four identical electrical lamps are labelled 1.5V, 0.5A 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
[UPSEAT 2001]
Options:
A) The value of R for normal brightness of each lamp is (3/4) W
B) The value of R for normal brightness of each lamp is (21/4) W
C) Total power dissipated in circuit when all lamps are normally bright is 24W
D) Power dissipated in R is 21W when all lamps are normally bright
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Answer:
Correct Answer: B
Solution:
For normal brightness of each bulb see following circuit. Current through each bulb = 0.5 A So main current $ i=2A $ Also, voltage across the combination $ =1.5,V $ So voltage across the resistance $ =10.5,V $ Hence for resistance $ V=i,R $
Therefore $ 10.5=2\times R $
Therefore $ R=\frac{21}{4}\Omega $
BETA
