Question

A resistance wire of $72\,\Omega$ is connected across 120 V dc source. When a similar wire is connected in paralllel with the first wire, change in power dissipated is

• A. $400\,\Omega$
• B. $200\,\Omega$
• C. $800\,\Omega$
• D. $100\,\Omega$

Answer 1

Answer: (B)

$200\,\Omega$

Answer 2

Using, P = $\frac{V^2}{R}$ we have P' = $\frac{V^2}{R/2} = \frac{120 \times 120}{72}$ = 40 W and
P = $\frac{V^2}{R} = \frac{120 \times 120}{72}$ = 200 W
Thus, $\Delta$P = 400 - 200 = 200 W