1
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
2
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
3
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
4
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
A LCR circuit behaves like a damped harmonic oscillator. Comparing it with a physical spring-mass damped oscillator having damping constant 'b', the correct equivalence would be:
A
L $$\leftrightarrow$$ k, C $$\leftrightarrow$$ b, R $$\leftrightarrow$$ m
B
L $$\leftrightarrow$$ m, C $$\leftrightarrow$$ k, R $$\leftrightarrow$$ b
C
L $$\leftrightarrow$$ m, C $$\leftrightarrow$$ $${1 \over k}$$, R $$\leftrightarrow$$ b
D
L $$\leftrightarrow$$ $${1 \over b}$$, C $$\leftrightarrow$$ $${1 \over m}$$, R $$\leftrightarrow$$ $${1 \over k}$$
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