Two 220 volt, 100 watt bulbs are connected first in series and then...

Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be:

Options

A50 watt, 10 watt
B100 watt, 50 watt
C200 watt, 150 watt
D50 watt, 200 watt

Correct answer

D. 50 watt, 200 watt

Step-by-step solution

\begin{aligned} & \mathrm{R}_1=\frac{\mathrm{V}^2}{\mathrm{P}_1}=\frac{(220)^2}{100}=484 \Omega \\ & \mathrm{R}_2=\frac{\mathrm{V}^2}{\mathrm{P}_2}=\frac{(220)^2}{100}=484 \Omega \\ & \mathrm{I}=\frac{220}{484 \times 2}=\frac{5}{22} \\ & \mathrm{P}=\mathrm{I}^2\left(\mathrm{R}_1+\mathrm{R}_2\right)=\frac{25}{22 \times 22} \times(484 \times 2) \\ & =50 \mathrm{~W}\end{aligned}

)

\begin{aligned} & P=\frac{V^2}{R_1}+\frac{V^2}{R_2} \\ & =\frac{2 \times(220)^2}{484}=200 \mathrm{~W}\end{aligned}

)

Practice Alternating Current on Quantrex Academy →

More from Alternating Current