JEE Advanced2017PhysicsAlternating CurrentActual
In the circuit shown, L = 1 μ H , C = 1 μ F a n d R = 1 k Ω . They are connected in series with an a.c. source V = V 0 sin ω t as shown. Which of the following options is/are correct?
Options
- AAt ω ≫ 10 6 r a d sec - 1 the circuit behaves as a capacitor
- BThe frequency at which the current will be in phase with the voltage is independent of R
- CThe current will be in phase with the voltage if ω = 10 4 r a d sec - 1
- DAt ω ~ 0 the current flowing through the circuit becomes nearly zero
Correct answer
B. The frequency at which the current will be in phase with the voltage is independent of R
Step-by-step solution
The current will be in phase with voltage when phase angle is zero, ∴ tan ⁡ ϕ = ω L - 1 ω C R = 0 Where ω ,   L ,   C ,   R are the angular frequency, inductance, capacitance and resistance respectively. ⇒ ω = ω 0 = 1 L C ⇒ ω ο is independent of R ⇒ ( r e s o n a n t   f r e q u e n c y )   ω 0 = 10 6   r a d / s Current in the circuit is given by, i 0 = V 0 R 2 + ω L - 1 ω C 2 When ω → 0 ,