KVPY SX SB Exam 2018 Question Paper

Question : 30 of 120

Marks: +1, -0

The current is flowing along the path abcd of a cube (shown to the left) produces a magnetic field at the centre of cube of magnitude B. Dashed line depicts the non-conducting part of the cube.

Consider a cubical shape shown to the right which is identical in size and shape to the left. If the same currentnow flows in along the path daefgcd, then the magnitude of magnetic field at the centre will be :-

zero
$√ 2B$
$√3B$
B

Validate

Solution:

From symmetry

B ↖{→}=B_x i↖{\^}+ B_y (– j ↖{\^})+ B_z k ↖{\^}

and

B_x = B_y = B_z = B\and \so B_\net = √3B

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