Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Advanced2016PhysicsAlternating CurrentActual

In the circuit shown below, the key is pressed at time t = 0. Which of the following statement(s) is(are) true?

Options

  1. AThe voltmeter displays -5V as soon as the key is pressed, and displays +5V after a long time
  2. BThe voltmeter will display 0 V at time t = ln 2 seconds
  3. CThe current in the ammeter becomes 1/e of the initial value after 1 second
  4. DThe current in the ammeter becomes zero after a long time

Correct answer

A. The voltmeter displays -5V as soon as the key is pressed, and displays +5V after a long time

Step-by-step solution

(i) At t = 0, capacitor acts as short - circuit The the reading of voltmeter will be -5 V At t → ∞ , capacitor acts as open circuit and no current flows through voltmeter. If it is ideal voltmeter then its resistance is infinite & therefore it will read +5V (ii) The Charge on the capacitor is given by q = q 0 ( 1 - e - t / RC ) as q 0 = RC is the max charge stored For C 1 =2C=40 μ F, R 1 =R=25 k q x = 2 CV 1 - e - t 2 CR The current through resistance of R=25 k is x = V R e - t 2 CR For C 2 =C=20 μ F, R 2 =2R=50 k

Practice Alternating Current on Quantrex Academy →

More from Alternating Current

Consider a circuit consisting of a capacitor of capacitance C and a coil with N turns per unit length, cross sectional area S and length d , where d^2 S . There is another coil of 2026A LCR series circuit driven with E_ rms = 90 V at frequency f_d = 30 Hz has resistance R = 80 , , an inductance with inductive reactance X_L = 20.0 , and capacitance with capacitiv 2026A series LCR circuit with R = 20 , L = 1.6 H and C = 40 F is connected to a variable frequency a.c. source. The inductive reactance at resonant frequency is _______ . 2026An a.c. source of angular frequency is connected across a resistor R and a capacitor C in series. The current is observed as I . Now the frequency of the source is changed to /4 , 2026An inductor of 10 mH, capacitor of 0.1 F and a resistor of 100 are connected in series across an a.c power supply 220 V, 70 Hz. The power factor of the given circuit is 0.5 . The d 2026The figure given below shows an LCR series circuit with two switches S₁ and S₂ . When switch S₁ is closed keeping S₂ open, the phase difference ( ) between the current and source v 2026An inductor stores 16 J of magnetic field energy and dissipates 32 W of thermal energy due to its resistance when an a.c. current of 2 A (rms) and frequency 50 Hz flows through it. 2026The electric current in the circuit is given as i=i_ o (t / T) . The r.m.s current for the period t=0 to t=T is _ _ _ _ . 2026 Full Alternating Current list All JEE Advanced PYQs