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NEET 2009
Exam
NEET
Year
2009
Subject
Physics
Chapter
Alternating Current

NEET 2009 · Physics · Alternating Current

Power dissipated in an L-C-R series circuit connected to an AC...

Power dissipated in an L−C−RL-C-R series circuit connected to an AC source of emf ε\varepsilon is

Options

  1. Aε2R[R2+(Lω−1Cω)2]\frac{\varepsilon^2 R}{\left[R^2+\left(L \omega-\frac{1}{C \omega}\right)^2\right]}
  2. B\frac{\varepsilon^2 \sqrt{\mathrm{R}^2+\left(\mathrm{L} \omega-\frac{1}{\mathrm{C} \omega}\right)^2}}{\mathrm{R}}
  3. Cε2[R2+(Lω−1Cω)2]R\frac{\varepsilon^2\left[\mathrm{R}^2+\left(\mathrm{L} \omega-\frac{1}{\mathrm{C} \omega}\right)^2\right]}{\mathrm{R}}
  4. D\frac{\varepsilon^2 R}{\sqrt{R^2+\left(L \omega-\frac{1}{C \omega}\right)^2}}

Correct answer

A. ε2R[R2+(Lω−1Cω)2]\frac{\varepsilon^2 R}{\left[R^2+\left(L \omega-\frac{1}{C \omega}\right)^2\right]}

Step-by-step solution

The emf of an LCR circuit is (\varepsilon). The impedance of a series LCR circuit is given as, (Z=\sqrt{\left[R^2+\left(\omega L-\frac{1}{\omega C}\right)^2\right]}) The power factor in a series LCR circuit is given as, (\cos \phi=\frac{\mathrm{R}}{|\mathrm{Z}|}) The power dissipated in the circuit is given as, (P=VrmsIrmscos⁡ϕ=ε×ε∣Z∣×R∣Z∣=ε2R[R2+(ωL−1ωC)2]\begin{aligned} & \mathrm{P}=\mathrm{V}_{\mathrm{rms}} \mathrm{I}_{\mathrm{rms}} \cos \phi \\ & =\varepsilon \times \frac{\varepsilon}{|\mathrm{Z}|} \times \frac{\mathrm{R}}{|\mathrm{Z}|} \\ & =\frac{\varepsilon^2 \mathrm{R}}{\left[\mathrm{R}^2+\left(\omega \mathrm{L}-\frac{1}{\omega \mathrm{C}}\right)^2\right]} \end{aligned}) Thus, the power dissipated in the series LCRL C R circuit is (\frac{\varepsilon^2 R}{\left[R^2+\left(\omega L-\frac{1}{\omega C}\right)^2\right]}).
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