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1
JEE Main 2021 (Online) 18th March Evening Shift
+4
-1
The time taken for the magnetic energy to reach 25% of its maximum value, when a solenoid of resistance R, inductance L is connected to a battery, is :
A
infinite
B
$${L \over R}$$ ln10
C
$${L \over R}$$ ln2
D
$${L \over R}$$ ln5
2
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
In a series LCR resonance circuit, if we change the resistance only, from a lower to higher value :
A
The bandwidth of resonance circuit will increase.
B
The resonance frequency will increase.
C
The quality factor will increase.
D
The quality factor and the resonance frequency will remain constant.
3
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
An AC source rated 220 V, 50 Hz is connected to a resistor. The time taken by the current to change from its maximum to the rms value is :
A
2.5 ms
B
25 ms
C
2.5 s
D
0.25 ms
4
JEE Main 2021 (Online) 17th March Evening Shift
+4
-1
Match List - I with List - II

List - I List - II
(a) Phase difference between current and voltage in a purely resistive AC circuit (i) $${\pi \over 2}$$; current leads voltage
(b) Phase difference between current and voltage in a pure inductive AC circuit (ii) zero
(c) Phase difference between current and voltage in a pure capacitive AC circuit (iii) $${\pi \over 2}$$; current lags voltage
(d) Phase difference between current and voltage in an LCR series circuit (iv) $${\tan ^{ - 1}}\left( {{{{X_C} - {X_L}} \over R}} \right)$$

Choose the most appropriate answer from the options given below :
A
(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
B
(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
C
(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
D
(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
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