1
JEE Main 2021 (Online) 18th March Morning Shift
MCQ (Single Correct Answer)
+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
2
JEE Main 2021 (Online) 17th March Evening Shift
MCQ (Single Correct Answer)
+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)
3
JEE Main 2021 (Online) 17th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
What happens to the inductive reactance and the current in a purely inductive circuit if the frequency is halved?
A
Both, inducting reactance and current will be doubled.
B
Inductive reactance will be doubled and current will be halved.
C
Both, inductive reactance and current will be halved.
D
Inductive reactance will be halved and current will be doubled.
4
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
An AC current is given by I = I1 sin$$\omega$$t + I2 cos$$\omega$$t. A hot wire ammeter will give a reading :
A
$${{{I_1} + {I_2}} \over {\sqrt 2 }}$$
B
$$\sqrt {{{I_1^2 - I_2^2} \over 2}}$$
C
$$\sqrt {{{I_1^2 + I_2^2} \over 2}}$$
D
$${{{I_1} + {I_2}} \over {2\sqrt 2 }}$$
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