1
JEE Main 2021 (Online) 31st August Morning Shift
+4
-1
A small square loop of side 'a' and one turn is placed inside a larger square loop of side b and one turn (b >> a). The two loops are coplanar with their centres coinciding. If a current I is passed in the square loop of side 'b', then the coefficient of mutual inductance between the two loops is :
A
$${{{\mu _0}} \over {4\pi }}8\sqrt 2 {{{a^2}} \over b}$$
B
$${{{\mu _0}} \over {4\pi }}{{8\sqrt 2 } \over a}$$
C
$${{{\mu _0}} \over {4\pi }}8\sqrt 2 {{{b^2}} \over a}$$
D
$${{{\mu _0}} \over {4\pi }}{{8\sqrt 2 } \over b}$$
2
JEE Main 2021 (Online) 27th August Evening Shift
+4
-1
A constant magnetic field of 1T is applied in the x > 0 region. A metallic circular ring of radius 1m is moving with a constant velocity of 1 m/s along the x-axis. At t = 0s, the centre of O of the ring is at x = $$-$$1m. What will be the value of the induced emf in the ring at t = 1s? (Assume the velocity of the ring does not change.)

A
1V
B
2$$\pi$$V
C
2V
D
0V
3
JEE Main 2021 (Online) 27th August Morning Shift
+4
-1
A bar magnet is passing through a conducting loop of radius R with velocity $$\upsilon$$. The radius of the bar magnet is such that it just passes through the loop. The induced e.m.f. in the loop can be represented by the approximate curve :

A
B
C
D
4
JEE Main 2021 (Online) 26th August Morning Shift
+4
-1
An inductor coil stores 64 J of magnetic field energy and dissipates energy at the rate of 640 W when a current of 8A is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit in seconds :
A
0.4
B
0.8
C
0.125
D
0.2
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