1
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A planar loop of wire rotates in a uniform magnetic field. Initially at t = 0, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of 10 s about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at :
A
2.5 s and 7.5 s
B
5.0 s and 10.0 s
C
5.0 s and 7.5 s
D
2.5 s and 5.0 s
2
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An emf of 20 V is applied at time t = 0 to a circuit containing in series 10 mH inductor and 5 $$\Omega $$ resistor. The ratio of the currents at time t = $$\infty $$ and at t = 40 s is close to : (Take e2 = 7.389)
A
1.06
B
0.84
C
1.15
D
1.46
3
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A particle of mass m and charge q has an initial velocity $$\overrightarrow v = {v_0}\widehat j$$ . If an electric field $$\overrightarrow E = {E_0}\widehat i$$ and magnetic field $$\overrightarrow B = {B_0}\widehat i$$ act on the particle, its speed will double after a time:
A
$${{3m{v_0}} \over {q{E_0}}}$$
B
$${{\sqrt 2 m{v_0}} \over {q{E_0}}}$$
C
$${{\sqrt 3 m{v_0}} \over {q{E_0}}}$$
D
$${{2m{v_0}} \over {q{E_0}}}$$
4
JEE Main 2020 (Online) 7th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Mass per unit area of a circular disc of radius $$a$$ depends on the distance r from its centre as $$\sigma \left( r \right)$$ = A + Br . The moment of inertia of the disc about the axis, perpendicular to the plane and assing through its centre is:
A
$$2\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
B
$$\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
C
$$2\pi {a^4}\left( {{{aA} \over 4} + {B \over 5}} \right)$$
D
$$2\pi {a^4}\left( {{A \over 4} + {B \over 5}} \right)$$
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