1
JEE Main 2020 (Online) 2nd September Morning Slot
+4
-1
A plane electromagnetic wave, has
frequency of 2.0 $$\times$$ 1010 Hz and its energy density is 1.02 $$\times$$ 10–8 J/m3 in vacuum. The amplitude of the magnetic field of the wave is close to
( $${1 \over {4\pi {\varepsilon _0}}} = 9 \times {10^9}{{N{m^2}} \over {{C^2}}}$$ and speed of light
= 3 $$\times$$ 108 ms–1)
A
190 nT
B
150 nT
C
160 nT
D
180 nT
2
JEE Main 2020 (Online) 9th January Evening Slot
+4
-1
In LC circuit the inductance L = 40 mH and
capacitance C = 100 $$\mu$$F. If a voltage
V(t) = 10sin(314t) is applied to the circuit, the
current in the circuit is given as :
A
0.52 cos 314 t
B
5.2 cos 314 t
C
0.52 sin 314 t
D
10 cos 314 t
3
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
$${{\varepsilon R} \over {e{L^2}}}$$
4
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
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
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