MHT CET202124 Sep 2021Morning ShiftPhysicsAlternating CurrentActual
A circuit containing resistance R ₁ , inductance L ₁ and capacitance C ₁ connected in series resonates at the same frequency ' f _ r ' as another circuit containing R ₂, ~L ₂ and C ₂ in series. If two circuits are connected in series, then the new frequency at resonance is
Options
- A3 4 f_r
- B3 2 f_r
- C2 f _ r
- Df _ r
Correct answer
D. f _ r
Step-by-step solution
When R ₁, ~L ₁ and C ₁ are connected in series the resonant (angular) frequency is given by _ r = 1 L ₁ C ₁ Also, when R ₂, ~L ₂, C ₂ are connected in series Then _ r = 1 L ₂ C ₂ By (1) and (2): L ₁ C ₁= L ₂ C ₂ If the two circuits are connected in series then the equivalent inductance is given by L = L ₁+ L ₂ and the equivalent capacitance is given by aligned & C = C ₁ C ₂ C ₁+ C ₂ & LC = ( L ₁+ L ₂ ) C ₁ C ₂ C ₁+ C ₂ & = L ₁ C ₁ C ₂+ L ₂ C ₁ C ₂ C ₁+ C ₂ [ L ₁ C ₁= L ₂ C ₂ ] & = L ₂ C ₂ ( C ₂+ C ₁ ) C ₁+ C ₂ = L