Question Details

he circuit shown in the figure contains an inductor 𝐿, a capacitor 𝐢0, a resistor 𝑅0 and an ideal battery. The circuit also contains two keys K1 and K2. Initially, both the keys are open and there is no charge on the capacitor. At an instant, key K1 is closed and immediately after this the current in 𝑅0 is found to be 𝐼1. After a long time, the current attains a steady state value 𝐼2. Thereafter, K2 is closed and simultaneously K1 is opened and the voltage across 𝐢0 oscillates with amplitude 𝑉0 and angular frequency πœ”0.

Match the quantities mentioned in List-I with their values in List-II and choose the correct option.

List-I List-II
(P) The value of 𝐼1 in Ampere is (1) 0
(Q) The value of 𝐼2 in Ampere is (2) 2
(R) The value of πœ”0 in kilo-radians/s is (3) 4
(S) The value of 𝑉0 in Volt is (4) 20

(5) 200

Options

A

P β†’ 1; Q β†’ 3; R β†’ 2; S β†’ 5

B

P β†’ 1; Q β†’ 2; R β†’ 3; S β†’ 5

C

P β†’ 1; Q β†’ 3; R β†’ 2; S β†’ 4

D

P β†’ 2; Q β†’ 5; R β†’ 3; S β†’ 4

Show Answer

Correct Answer :

Option A

P β†’ 1; Q β†’ 3; R β†’ 2; S β†’ 5

P β†’ 1; Q β†’ 3; R β†’ 2; S β†’ 5

Solution :

Correct Option: P β†’ 1; Q β†’ 3; R β†’ 2; S β†’ 5

To solve this problem, we analyze the circuit configurations step-by-step using the values given in the circuit diagram:
- Battery Voltage, V=20 V
- Resistor, R0=5 Ξ©
- Inductor, L=25 mH
- Capacitor, C0=10 ΞΌF

Step 1: Finding I1 (Immediately after closing K1)
Initially, both switches K1 and K2 are open, and there is no current in the inductor. At t=0, switch K1 is closed while K2 remains open. An inductor opposes any sudden change in current. Since the current through the inductor was 0 just before closing the switch, it must remain 0 immediately after closing the switch:
IL(0+)=0
Because the capacitor branch is open, the current flowing through R0 is the same as the current through the inductor. Thus, the initial current I1 is:
I1=0 A
This corresponds to P β†’ 1.

Step 2: Finding I2 (After a long time in steady state)
After a long time, the circuit reaches a steady state. In a DC circuit, an inductor acts as a short circuit (zero resistance) at steady state. The current flows from the battery, through the resistor R0, and through the shorted inductor L back to the battery. The steady-state current I2 is:
I2=VR0=205=4 A
This corresponds to Q β†’ 3.

Step 3: Finding the angular frequency Ο‰0
When K2 is closed and K1 is opened simultaneously, the battery and the resistor R0 are disconnected from the loop containing the inductor L and the capacitor C0. This forms a closed, parallel LC oscillating circuit. The angular frequency of oscillation Ο‰0 is:
Ο‰0=1LC0
Substituting the given values:
Ο‰0=125Γ—10-3Γ—10Γ—10-6=1250Γ—10-9=125Γ—10-8=15Γ—10-4=2000 rad/s=2 kilo-rad/s
This corresponds to R β†’ 2.

Step 4: Finding the amplitude of the voltage oscillation V0
At the instant K1 is opened and K2 is closed, the current flowing in the inductor is I2=4 A and the charge on the capacitor is zero. The total energy stored in the LC circuit is equal to the initial magnetic energy of the inductor:
E=12LI22
During the oscillation, the maximum voltage across the capacitor V0 occurs when all the electromagnetic energy is stored in the electric field of the capacitor:
12C0V02=12LI22
Solving for V0:
V0=I2LC0
Substituting the values:
V0=4Γ—25Γ—10-310Γ—10-6=4Γ—2500=4Γ—50=200 V
This corresponds to S β†’ 5.

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