KVPY 2020-21 SB SX Exam Previous Papers

Question : 93 of 120

Marks: +1, -0

Imagine a world where free magnetic charges exist. In this world, a circuit is made with a U shape wire and a rod free to slide on it. A current carried by free magnetic charges can flow in the circuit. When the circuit is placed in a uniform electric field, E perpendicular to the plane of the circuit and the rod is pulled to the right with a constant speed v, the "magnetic EMF" in the current and the direction of the corresponding current, arising because of changing electric flux will be ( l is the length of the rod and c is speed of light ).

$v E l$ clockwise
$v E L$ counterclockwise
${v E l}/{c^{2}}$ clockwise.
${v E l}/{c^{2}}$ counterclockwise

Validate

Solution:

∮ {{B}↖{→}} \.{{d} l}↖{→}=\µ_{0}({I}+\ε_{0}({{d} \ϕ_{{E}}}/{{dt}}))

{{d} \ϕ_{{E}}}/{{dt}}={vE} l

\∴\∮ {{B}↖{→}} {{d} l}↖{→}=\µ_{0} \ε_{0}({vE} l) \⇒ {{vE} l}/{{C}^{2}}

Direction of electric field is not given in the question therefore both options are possible.

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