1
JEE Advanced 2020 Paper 1 Offline
+3
-1
A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc, the disc will (figure is schematic and not drawn to scale)
A
rotate in the direction opposite to the direction of magnet’s motion
B
rotate in the same direction as the direction of magnet’s motion
C
not rotate and its temperature will remain unchanged
D
not rotate but its temperature will slowly rise
2
JEE Advanced 2020 Paper 1 Offline
+3
-1
An open-ended U-tube of uniform cross-sectional area contains water (density 103 kg m−3 ). Initially the water level stands at 0.29 m from the bottom in each arm. Kerosene oil (a water-immiscible liquid) of density 800 kg m−3 is added to the left arm until its length is 0.1 m, as shown in the schematic figure below. The ratio $$\left( {{{{h_1}} \over {{h_2}}}} \right)$$ of the heights of the liquid in the two arms is :
A
$${{15} \over {14}}$$
B
$${{35} \over {33}}$$
C
$${7 \over 6}$$
D
$${5 \over 4}$$
3
JEE Advanced 2020 Paper 1 Offline
MCQ (More than One Correct Answer)
+4
-2
The filament of a light bulb has surface area 64 mm2 . The filament can be considered as a black body at temperature 2500 K emitting radiation like a point source when viewed from far. At night the light bulb is observed from a distance of 100 m. Assume the pupil of the eyes of the observer to be circular with radius 3 mm. Then

(Take Stefan-Boltzmann constant = 5.67 $$\times$$ 10−8 Wm−2K−4 , Wien’s displacement constant = 2.90 $$\times$$ 10−3 m-K, Planck’s constant = 6.63 $$\times$$ 10−34 Js, speed of light in vacuum = 3.00 $$\times$$ 108 ms−1)
A
power radiated by the filament is in the range 642 W to 645 W
B
radiated power entering into one eye of the observer is
in the range 3.15 $$\times$$ 10−8 W to 3.25 $$\times$$ 10−8 W
C
the wavelength corresponding to the maximum intensity of light is 1160 nm
D
taking the average wavelength of emitted radiation to be 1740 nm, the total number of photons entering per second into one eye of the observer is in the range 2.75 $$\times$$ 1011 to 2.85 $$\times$$ 1011
4
JEE Advanced 2020 Paper 1 Offline
MCQ (More than One Correct Answer)
+4
-2
Sometimes it is convenient to construct a system of units so that all quantities can be expressed in terms of only one physical quantity. In one such system, dimensions of different quantities are given in terms of a quantity X as follows: [position] = [X$$\alpha$$]; [speed] = [X$$\beta$$ ]; [acceleration] = [Xp]; [linear momentum] = [Xq]; [force] = [Xr]. Then
A
$$\alpha$$ + p = 2$$\beta$$
B
p + q - r = $$\beta$$
C
p - q + r = $$\alpha$$
D
p + q + r = $$\beta$$
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