EASY
12th West Bengal Board
IMPORTANT
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Two long straight parallel wires are 2 m apart, perpendicular to the plane of the paper, Fig. The wire A carries a current of 9.6 A, directed into the plane of the paper. The wire B carries a current such that the magnetic field of induction at the point P, at distance 1011 m from the wire B is zero. Find The force per unit length on the wire B.

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Important Questions on Electromagnetism

MEDIUM
12th West Bengal Board
IMPORTANT

A wire loop carrying a current l is placed in the x y plane as shown in Fig. If a particle with charge Q and mass m is placed at the centre P and given a velocity v along NP. Find its instantaneous acceleration. 

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EASY
12th West Bengal Board
IMPORTANT

A wire loop carrying a current I is placed in the x -y plane as shown in Fig. acceleration. If an external uniform magnetic induction field B=Bi^ is applied, find the force and the torque acting on the loop due to this field.

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EASY
12th West Bengal Board
IMPORTANT

An electron gun G emits electrons of energy 2 keV travelling in the positive X -direction. The electrons are required to hit the spot S where GS=0.1 m, and the line GS make an angle 60° with the X -axis is as shown in Fig. A uniform magnetic field B parallel to GS exists in the region outside the electron gun. Find the minimum value of B needed to make the electron hit S . 

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HARD
12th West Bengal Board
IMPORTANT

A long horizontal wire AB, which is free to move in a vertical plane and carries a steady current of 20 A, is in equilibrium at highest of 0.01 m over another parallel long wire CD which is fixed in a horizontal plane and carries a steady current of 30 A, as shown in figure. Show that when AB is slightly depressed, it executes simple harmonic motion. Find the period of oscillations.

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EASY
12th West Bengal Board
IMPORTANT
Three infinitely long thin wires, each carrying current i in the same direction are in the x-y plane of a gravity-free space. The central wire is along the Y -axis while the other two are along x=±d. find the locus of the points for which the magnetic field is zero. 
EASY
12th West Bengal Board
IMPORTANT
Three infinitely long thin wires, each carrying current i in the same direction are in the x-y plane of a gravity-free space. The central wire is along the Y -axis while the other two are along x=±d. If the central wire is displaced along the Z -direction by a small amount and released, show that it will execute simple harmonic motion. If the linear density of the wire is λ, find the frequency of oscillation.
MEDIUM
12th West Bengal Board
IMPORTANT

The region between x=0 and x=L is filled with a uniform steady magnetic field B0k^. A particle of mass m, positive charge q and velocity v0i^ travels along X -axis and enters the region of the magnetic field. Neglect the gravity throughout the question.

(a) Find the value of L if the particle emerges from the region of the magnetic field with its final velocity at an angle 30° to its initial velocity. 

HARD
12th West Bengal Board
IMPORTANT

The region between x=0 and x=L is filled with a uniform steady magnetic field   B0k^. A particle of mass m, positive
charge q and velocity v0i^ travels along X -axis and enters the region of the magnetic field. Neglect the gravity throughout the question.

(b) Find the final velocity of the particle and the time spent by it in the magnetic field, if the magnetic field now expands upto 2.1 L.