JEE Main 2020 (Online) 9th January Evening Slot | Magnetics Question 157 | Physics

JEE Main 2020 (Online) 9th January Evening Slot

MCQ (Single Correct Answer)

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An electron gun is placed inside a long solenoid of radius R on its axis. The solenoid has n turns/length and carries a current I. The electron gun shoots an electron along the radius of the solenoid with speed v. If the electron does not hit the surface of the solenoid, maximum possible value of v is (all symbols have their standard meaning) : JEE Main 2020 (Online) 9th January Evening Slot Physics - Magnetics Question 159 English

JEE Main 2020 (Online) 9th January Evening Slot Physics - Magnetics Question 159 English

$${{e{\mu _0}nIR} \over {4m}}$$

$${{e{\mu _0}nIR} \over m}$$

$${{e{\mu _0}nIR} \over {2m}}$$

$${{2e{\mu _0}nIR} \over m}$$

JEE Main 2020 (Online) 9th January Evening Slot

MCQ (Single Correct Answer)

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A plane electromagnetic wave is propagating along the direction $${{\widehat i + \widehat j} \over {\sqrt 2 }}$$ , with its polarization along the direction $$\widehat k$$ . The correct form of the magnetic field of the wave would be (here B₀ is an appropriate constant) :

$${B_0}{{\widehat i - \widehat j} \over {\sqrt 2 }}\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$

$${B_0}{{\widehat i + \widehat j} \over {\sqrt 2 }}\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$

$${B_0}{{\widehat j - \widehat i} \over {\sqrt 2 }}\cos \left( {\omega t + k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$

$${B_0}\widehat k\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$

JEE Main 2020 (Online) 9th January Evening Slot

MCQ (Single Correct Answer)

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A small circular loop of conducting wire has radius a and carries current I. It is placed in a uniform magnetic field B perpendicular to its plane such that when rotated slightly about its diameter and released, it starts performing simple harmonic motion of time period T. If the mass of the loop is m then :

$$T = \sqrt {{{2m} \over {IB}}} $$

$$T = \sqrt {{{\pi m} \over {IB}}} $$

$$T = \sqrt {{{\pi m} \over {2IB}}} $$

$$T = \sqrt {{{2\pi m} \over {IB}}} $$

JEE Main 2020 (Online) 9th January Morning Slot

MCQ (Single Correct Answer)

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A long, straight wire of radius a carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distance $${a \over 3}$$ and 2$$a$$, respectively from the axis of the wire is :

$${1 \over 2}$$

$${3 \over 2}$$

$${2 \over 3}$$

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