Four identical electrical lamps are labelled | vedclass

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(B) For normal brightness of each bulb,the voltage across each bulb must be $1.5\,V$ and the current through each bulb must be $0.5\,A$.Since the four

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The value of $R$ for normal brightness of each lamp is $(21/4)\,\Omega$.

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(B) For normal brightness of each bulb,the voltage across each bulb must be $1.5\,V$ and the current through each bulb must be $0.5\,A$.Since the four bulbs are connected in parallel,the total current $i$ flowing through the circuit is the sum of the currents through each bulb: $i = 0.5\,A + 0.5\,A + 0.5\,A + 0.5\,A = 2\,A$.The voltage across the parallel combination of bulbs is $1.5\,V$.Since the battery voltage is $12\,V$,the voltage across the resistor $R$ is $V_R = 12\,V - 1.5\,V = 10.5\,V$.Using Ohm's law for the resistor $R$,$V_R = i 	imes R$,we get $10.5\,V = 2\,A 	imes R$.Therefore,$R = 10.5 / 2 = 21/4\,\Omega$.

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 the lamps as shown. Then:

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