Physics - Magnetism Question with Solution | TestHub

PhysicsMagnetismMagnetic torque & energyMedium2 minPYQ_2020

PhysicsMediumsingle choice

A metallic wire is folded to form a square loop of side $a$ . It carries a current $i$ and is kept perpendicular to a uniform magnetic field. If the shape of the loop is changed from square to a circle without changing the length of the wire and current, the amount of work done in doing so is

Options:

Answer:

Solution:

$W = U_{f} - U_{i}$

$= (- M_{f} B {cos 0}^{o}) - (- M_{i} B cos 0^{o})$

$= i B (A_{i} - A_{f})$

where $A_{i} = a^{2} {,A}_{f} = π R^{2} = \frac{4 a^{2}}{π}$

as $2 π R = 4 a or R = \frac{2 a}{π}$

$∴ W = i B a^{2} (1 - \frac{4}{π})$

Stream:JEESubject:PhysicsTopic:MagnetismSubtopic:Magnetic torque & energy

⏱ 2mℹ️ Source: PYQ_2020

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