1
JEE Main 2023 (Online) 25th January Morning Shift
+4
-1

In an LC oscillator, if values of inductance and capacitance become twice and eight times, respectively, then the resonant frequency of oscillator becomes $$x$$ times its initial resonant frequency $$\omega_0$$. The value of $$x$$ is :

A
1/4
B
1/16
C
4
D
16
2
JEE Main 2022 (Online) 29th July Evening Shift
+4
-1

A circuit element $$\mathrm{X}$$ when connected to an a.c. supply of peak voltage $$100 \mathrm{~V}$$ gives a peak current of $$5 \mathrm{~A}$$ which is in phase with the voltage. A second element $$\mathrm{Y}$$ when connected to the same a.c. supply also gives the same value of peak current which lags behind the voltage by $$\frac{\pi}{2}$$. If $$\mathrm{X}$$ and $$\mathrm{Y}$$ are connected in series to the same supply, what will be the rms value of the current in ampere?

A
$$\frac{10}{\sqrt{2}}$$
B
$$\frac{5}{\sqrt{2}}$$
C
$$5 \sqrt{2}$$
D
$$\frac{5}{2}$$
3
JEE Main 2022 (Online) 29th July Morning Shift
+4
-1

An alternating emf $$\mathrm{E}=440 \sin 100 \pi \mathrm{t}$$ is applied to a circuit containing an inductance of $$\frac{\sqrt{2}}{\pi} \mathrm{H}$$. If an a.c. ammeter is connected in the circuit, its reading will be :

A
4.4 A
B
1.55 A
C
2.2 A
D
3.11 A
4
JEE Main 2022 (Online) 29th July Morning Shift
+4
-1

A coil of inductance 1 H and resistance $$100 \,\Omega$$ is connected to a battery of 6 V. Determine approximately :

(a) The time elapsed before the current acquires half of its steady - state value.

(b) The energy stored in the magnetic field associated with the coil at an instant 15 ms after the circuit is switched on. (Given $$\ln 2=0.693, \mathrm{e}^{-3 / 2}=0.25$$)

A
t = 10 ms; U = 2 mJ
B
t = 10 ms; U = 1 mJ
C
t = 7 ms; U = 1 mJ
D
t = 7 ms; U = 2 mJ
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