JEE Main 2021 (Online) 31st August Morning Shift | Magnetics Question 80 | Physics

JEE Main 2021 (Online) 31st August Morning Shift

MCQ (Single Correct Answer)

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A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at centre, when a current I passes through coil:

$${{{\mu _0}IN} \over {2(b - a)}}{\log _e}\left( {{b \over a}} \right)$$

$${{{\mu _0}I} \over 8}\left[ {{{a + b} \over {a - b}}} \right]$$

$${{{\mu _0}I} \over {4(a - b)}}\left[ {{1 \over a} - {1 \over b}} \right]$$

$${{{\mu _0}I} \over 8}\left( {{{a - b} \over {a + b}}} \right)$$

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)

-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.)

JEE Main 2021 (Online) 27th August Evening Shift Physics - Magnetics Question 81 English

2$$\pi$$V

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)

-1

A coaxial cable consists of an inner wire of radius 'a' surrounded by an outer shell of inner and outer radii 'b' and 'c' respectively. The inner wire carries an electric current i₀, which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance x from the axis when (i) x < a and (ii) a < x < b ?

$${{{x^2}} \over {{a^2}}}$$

$${{{a^2}} \over {{x^2}}}$$

$${{{x^2}} \over {{b^2} - {a^2}}}$$

$${{{b^2} - {a^2}} \over {{x^2}}}$$

JEE Main 2021 (Online) 27th August Morning Shift

MCQ (Single Correct Answer)

-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 :

JEE Main 2021 (Online) 27th August Morning Shift Physics - Magnetics Question 86 English