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) 16th March Evening Shift
+4
-1
The magnetic field in a region is given by $$\overrightarrow B = {B_o}\left( {{x \over a}} \right)\widehat k$$. A square loop of side d is placed with its edges along the x and y axes. The loop is moved with a constant velocity $$\overrightarrow v$$ = v0$$\widehat i$$. The emf induced in the loop is : A
$${{{B_o}{v_o}{d^2}} \over {2a}}$$
B
$${{{B_o}v_o^2d} \over {2a}}$$
C
$${{{B_o}{v_o}d} \over {2a}}$$
D
$${{{B_o}{v_o}{d^2}} \over a}$$
3
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
A conducting bar of length L is free to slide on two parallel conducting rails as shown in the figure Two resistors R1 and R2 are connected across the ends of the rails. There is a uniform magnetic field $$\overrightarrow B$$ pointing into the page. An external agent pulls the bar to the left at a constant speed v.

The correct statement about the directions of induced currents I1 and I2 flowing through R1 and R2 respectively is :
A
Both I1 and I2 are in clockwise direction
B
I1 is in clockwise direction and I2 is in anticlockwise direction
C
I1 is in anticlockwise direction and I2 is in clockwise direction
D
Both I1 and I2 are in anticlockwise direction
4
JEE Main 2021 (Online) 26th February Evening Shift
+4
-1
An aeroplane, with its wings spread 10 m, is flying at a speed of 180 km/h in a horizontal direction. The total intensity of earth's field at that part is 2.5 $$\times$$ 10$$-$$4 Wb/m2 and the angle of dip is 60$$^\circ$$. The emf induced between the tips of the plane wings will be __________.
A
88.37 mV
B
62.50 mV
C
54.125 mV
D
108.25 mV
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Physics
Mechanics
Electricity
Optics
Modern Physics
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