JEE Main 2020 (Online) 7th January Evening Slot | Alternating Current and Electromagnetic Induction Question 147 | Physics

JEE Main 2020 (Online) 7th January Evening Slot

MCQ (Single Correct Answer)

-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)

1.06

0.84

1.15

1.46

JEE Main 2020 (Online) 7th January Morning Slot

MCQ (Single Correct Answer)

-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?

$$\phi $$_i = $$\phi $$₀

$$\phi $$_i < $$\phi $$₀

$$\phi $$_i $$>$$ $$\phi $$₀

$$\phi $$_i = - $$\phi $$₀

JEE Main 2020 (Online) 7th January Morning Slot

MCQ (Single Correct Answer)

-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 (I_R) and the induced EMF(V_R) in the ring change as :

Direction of I_R remains unchanged and V_R is zero at t = 0.25

Direction of I_R remains unchanged and V_R is maximum at t = 0.5

At t = 0.25 direction of I_R reverses and V_R is maximum

At t = 0.5 direction of I_R reverses and V_R is zero

JEE Main 2020 (Online) 7th January Morning Slot

MCQ (Single Correct Answer)

-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:

L $$ \leftrightarrow $$ k, C $$ \leftrightarrow $$ b, R $$ \leftrightarrow $$ m

L $$ \leftrightarrow $$ m, C $$ \leftrightarrow $$ k, R $$ \leftrightarrow $$ b

L $$ \leftrightarrow $$ m, C $$ \leftrightarrow $$ $${1 \over k}$$, R $$ \leftrightarrow $$ b

L $$ \leftrightarrow $$ $${1 \over b}$$, C $$ \leftrightarrow $$ $${1 \over m}$$, R $$ \leftrightarrow $$ $${1 \over k}$$

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