Question

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

• A. 1 watt
• B. 5 watt
• C. 4 watt
• D. 2 watt

Answer 1

Answer: (B)

5 watt

Answer 2

$2\, \Omega, 4\, \Omega$ and $(1\, \Omega+5\, \Omega)$ are in parallel.
So potential difference is the same.
$V=2\, \Omega \cdot i_1= 4\, \Omega \cdot \, i_2= 6\, \Omega\cdot i_3$
$2\cdot 3= 6\, \Omega\cdot i_3 \Rightarrow \, i_3= 1$ amp.
Total P.D.$=5\, \times 1\, +\, 1\, \times\, 1 =6\, V.$
$\therefore \, \, \,$ Power dissipated in $5\, \Omega$ resistance
$\, \, \, \, \, =\frac{V'^2}{R}$
where V' is the P.D. across $5\, \Omega= 5\, V.$
$\therefore$ Power $= \frac{25V^2}{5\, \Omega}=5$ watt