A current of 3 A flows through the $2 \Omega$ resistor shown in the circuit. The power dissipated in the $5…

A current of 3 A flows through the $2 \Omega$ resistor shown in the circuit. The power dissipated in the $5 \Omega$ resistor is
  1. $4 \mathrm{~W}$
  2. $2 \mathrm{~W}$
  3. $1 \mathrm{~W}$
  4. $5 \mathrm{~W}$

Solution

Key Idea : Voltage across $2 \Omega$ is same as voltage across arm containing $1 \Omega$ and $5 \Omega$ resistances. Voltage across $2 \Omega$ resistance,
$V=2 \times 3=6 \mathrm{~V}$
So, voltage across lowest arm,
$V_1=6 \mathrm{~V}$
Current across $5 \Omega, I=\frac{6}{1+5}=1 \mathrm{~A}$
Thus, power across $5 \Omega$,
$P=I^2 R=(1)^2 \times 5=5 \mathrm{~W}$

Asked in: NEET 2008 (Screening)

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