1
JEE Main 2020 (Online) 4th September Morning Slot
+4
-1
A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer G attached across the coil? Three positions shown describe :
(a) the magnet's entry
(b) magnet is completely inside and
(c) magnet's exit.
A B C D 2
JEE Main 2020 (Online) 3rd September Evening Slot
+4
-1
A uniform magnetic field B exists in a direction perpendicular to the plane of a square loop made of a metal wire. The wire has a diameter of 4 mm and a total length of 30 cm. The magnetic field changes with time at a steady rate $${{dB} \over {dt}}$$ = 0.032 Ts–1. The induced current in the loop is close to (Resistivity of the metal wire is 1.23 $$\times$$ 10–8 $$\Omega$$m)
A
0.53 A
B
0.43 A
C
0.34 A
D
0.61 A
3
JEE Main 2020 (Online) 3rd September Morning Slot
+4
-1
An elliptical loop having resistance R, of semi major axis a, and semi minor axis b is placed in magnetic field as shown in the figure. If the loop is rotated about the x-axis with angular frequency $$\omega$$, the average power loss in the loop due to Joule heating is : A
$${{\pi abB\omega } \over R}$$
B
$${{{\pi ^2}{a^2}{b^2}{B^2}{\omega ^2}} \over R}$$
C
$${{{\pi ^2}{a^2}{b^2}{B^2}{\omega ^2}} \over {2R}}$$
D
Zero
4
JEE Main 2020 (Online) 8th January Evening Slot
+4
-1
A shown in the figure, a battery of emf $$\varepsilon$$ is connected to an inductor L and resistance R in series. The switch is closed at t = 0. The total charge that flows from the battery, between t = 0 and t = tc (tc is the time constant of the circuit) is : A
$${{\varepsilon L} \over {e{R^2}}}$$
B
$${{\varepsilon L} \over {{R^2}}}$$
C
$${{\varepsilon L} \over {{R^2}}}\left( {1 - {1 \over e}} \right)$$
D
$${{\varepsilon R} \over {e{L^2}}}$$
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