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QJEEM17Ph9478: JEE Main 2017 Physics - Class 12 JEEM17Ph9478 Solution: A sinusoidal voltage of peak value 283 V and angular frequency…

A sinusoidal voltage of peak value 283 V and angular frequency 320/s is applied to a series LCR circuit. Given that R=5 Ω\Omega , L=25 mH and C=1000 μ\mu F. The total impedance, and phase difference between the voltage across the source and the current will respectively be :

Multiple Choice Options

  • A 10 Ω\Omega and tan −- 1 (53)\left( {{5 \over 3}} \right)
  • B 7 Ω7\,\Omega and 45o
  • C 10 Ω10\,\Omega and tan −- 1 (83)\left( {{8 \over 3}} \right)
  • D 7 Ω7\,\Omega and tan −- 1 (53)\left( {{5 \over 3}} \right)

Step-by-Step Verified Solution

It is given that e0 = 283 V; ω\omega = 320.

The inductor reactance is XL = 320 ×\times 25 ×\times 10 −- 3 = 8 Ω\Omega

The capacitor reactance is

XC=1ωC=1320×1000×10−6=1000320=3.1 Ω{X_C} = {1 \over {\omega C}} = {1 \over {320 \times 1000 \times {{10}^{ - 6}}}} = {{1000} \over {320}} = 3.1\,\Omega

It is given that R = 5 Ω\Omega . Therefore, the total impedance is

Z=R2+(XL−XC)2=50=7 ΩZ = \sqrt {{R^2} + {{({X_L} - {X_C})}^2}} = \sqrt {50} = 7\,\Omega

and the phase difference between the voltage across the source and the current is

tan⁡ϕ=XL−XCR=8−3.15≈1⇒θ=45∘\tan \phi = {{{X_L} - {X_C}} \over R} = {{8 - 3.1} \over 5} \approx 1 \Rightarrow \theta = 45^\circ

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