Question

I=3 amp flows through the 2ohm resistor the power dissipated in 5 ohm resistor is

Answer 1

use P=V^2/R to solve this

Answer 2

here you can see , $2\Omega$ and $5\Omega,1\Omega$ both are in parallel combination. so, potential difference across $5\Omega,1\Omega$ resistors are same potential difference across $2\Omega$ resistor.
from Ohm's law,
V = iR => V = 3 × 2 = 6V
hence, potential difference across 2ohm resistor is 6V
so, current passing through 5ohm resistor is V/Req = 6/(5 + 1) = 1A
so, potential across 5ohm resistor is 5 × 1 = 5V
now, power dissipation by 5ohm resistor = V²/R
= 5²/5 = 5W.