1
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
$${{\varepsilon R} \over {e{L^2}}}$$
2
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
3
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
Consider a circular coil of wire carrying constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane that contains the circular coil and excluding the circular coil area is given by $$\phi$$i. The magnetic flux through the area of the circular coil area is given by $$\phi$$0. Which of the following option is correct?
A
$$\phi$$i = $$\phi$$0
B
$$\phi$$i < $$\phi$$0
C
$$\phi$$i $$>$$ $$\phi$$0
D
$$\phi$$i = - $$\phi$$0
4
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
A long solenoid of radius R carries a time (t) - dependent current
I(t)=I0t(1 - t). A ring of radius 2R is placed coaxially near its middle. During the time interval 0 $$\le$$ t $$\le$$ 1, the induced current (IR) and the induced EMF(VR) in the ring change as :
A
Direction of IR remains unchanged and VR is zero at t = 0.25
B
Direction of IR remains unchanged and VR is maximum at t = 0.5
C
At t = 0.25 direction of IR reverses and VR is maximum
D
At t = 0.5 direction of IR reverses and VR is zero
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