Question Details

A series LCR circuit is connected to a 45 sin(ωt) Volt source. The resonant angular frequency of the circuit is 105 rad s−1 and current amplitude at resonance is I0. When the angular frequency of the source is ω = 8 × 104 rad s−1, the current amplitude in the circuit is 0.05 I0. If L = 50 mH, match each entry in List-I with an appropriate value from List-II and choose the correct option.


List-I List-II
(P) I0 in mA (1) 44.4
(Q) The quality factor of the circuit (2) 18
(R) The bandwidth of the circuit in rad s 1 (3) 400
(S) The peak power dissipated at resonance in Watt (4) 2250

(5) 500

Options

A

P → 2, Q → 3, R → 5, S → 1

B

P → 3, Q → 1, R → 4, S → 2

C

P → 4, Q → 5, R → 3, S → 1

D

P → 4, Q → 2, R → 1, S → 5

Show Answer

Correct Answer :

Option B

P → 3, Q → 1, R → 4, S → 2

Solution :

The correct option is P → 3, Q → 1, R → 4, S → 2.

Given Data:
Peak Voltage of the AC source, V0 = 45 V
Resonant angular frequency, ω0 = 105 rad s−1
Inductance, L = 50 mH = 50 × 10−3 H = 0.05 H
At angular frequency ω = 8 × 104 rad s−1, current amplitude I = 0.05 I0

Step-by-step Derivation:

1. Finding the Net Reactance at ω = 8 × 104 rad s−1:
The inductive reactance is XL = ωL and capacitive reactance is XC = 1/(ωC).
Since ω02 = 1/(LC), we have 1/C = ω02L.

Substituting 1/C in the net reactance X:

X=ωL-1ωC=Lω-ω02ω

Plugging in the given values:

X=0.05×8×104-10108×104

X=0.05×80000-125000=0.05×45000=2250 Ω

2. Determining Resistance R and Current Amplitude at Resonance I0 (P):
The current amplitude at frequency ω is given by:

I=V0R2+X2

At resonance, I0 = V0 / R. Given I = 0.05 I0:

V0R2+X2=0.05×V0RR2+X2=20R

R2+X2=400R2399R2=X2

R=X399225020=112.5 Ω

Now, calculate peak current I0:

I0=V0R=45112.5=0.4 A=400 mA

Thus, (P) → (3).

3. Calculating Quality Factor Q (Q):
The Quality factor of the circuit is given by:

Q=ω0LR=105×0.05112.5=5000112.5=44.4

Thus, (Q) → (1).

4. Calculating Bandwidth (R):
Bandwidth (Δω) is given by:

Δω=RL=112.50.05=2250 rad s1

Thus, (R) → (4).

5. Calculating Peak Power Dissipated at Resonance (S):
At resonance, maximum/peak power dissipated is:

P0=V0I0=45×0.4=18 Watt

Thus, (S) → (2).

Conclusion:
Matching the entries:
P → 3
Q → 1
R → 4
S → 2

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