HARD
JEE Main
IMPORTANT
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A small current-carrying coil, having a magnetic moment pm, is located at the axis of a round loop, of radius R, with current I flowing through it. Find the magnitude of the vector force applied to the coil, if its distance from the centre of the loop is equal to x, and the vector pm coincides in the direction with the axis of the loop.

Important Questions on ELECTRODYNAMICS

HARD
JEE Main
IMPORTANT
Find the interaction force of two coils with magnetic moments p1m=4.0 mA m2 and p2m=6.0 mA m2, and collinear axes, if the separation between the coils is equal to l=20 cm, which exceeds considerably their linear dimensions. (permeability of vacuum, μ0=1.257×10-6  H m-1)
HARD
JEE Main
IMPORTANT

A wire, bent as a parabola y=ax2, is located in a uniform magnetic field of induction B, the vector B being perpendicular to the plane x-y. At the moment t=0, a connector starts sliding translation-wise from the parabola apex, with a constant acceleration w. Find the emf of electromagnetic induction in the loop thus formed as a function of y.

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MEDIUM
JEE Main
IMPORTANT

A rectangular loop with a sliding connector of length I, is located in a uniform magnetic field perpendicular to the loop plane. The magnetic induction is equal to B. The connector has an electric resistance R, the sides AB and CD have resistances R1 and R2, respectively. Neglecting the self-inductance of the loop, find the current flowing in the connector during its motion, with a constant velocity v.

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HARD
JEE Main
IMPORTANT
A metal disc of radius a=25 cm, rotates with a constant angular velocity ω=130 rad s-1 about its axis. Find the potential difference between the centre and the rim of the disc, if
a the external magnetic field is absent;
b  the external uniform magnetic field of induction B=5.0 mT, is directed perpendicular to the disc.
HARD
JEE Main
IMPORTANT
A thin wire AC, shaped as a semi-circle of diameter d=20 cm, rotates with a constant angular velocity, ω=100 rad s-1, in a uniform magnetic field of induction B=5.0 mT, with ωB. The rotation axis passes through the end A of the wire and is perpendicular to the diameter AC. Find the value of a line integral E dr, along the wire, from point A to point C. Generalize the obtained result.
HARD
JEE Main
IMPORTANT

A wire loop, enclosing a semi-circle of radius a, is located on the boundary of a uniform magnetic field of induction B. At the moment t=0, the loop is set into rotation with a constant angular acceleration β, about an axis O, coinciding with a line of vector B, on the boundary. Find the emf induced in the loop as a function of time t. Draw the approximate plot of this function. The arrow in the figure shows the emf direction, taken to be positive.

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HARD
JEE Main
IMPORTANT

A long straight wire, carrying a current I, and a U-shaped conductor, with a sliding connector, are located in the same plane, as shown in the figure. The connector, of length L and resistance R, slides to the right with a constant velocity v. Find the current induced in the loop as a function of separation r between the connector and the straight wire. The resistance of the U-shaped conductor and the self inductance of the loop are assumed to be negligible.

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HARD
JEE Main
IMPORTANT

A square frame, with side a, and a long straight wire, carrying a current I, are located in the same plane, as shown in the figure. The frame translates to the right with a constant velocity U. Find the emf induced in the frame as a function of distance x.

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