A small square loop of wire of side l is placed inside a large square loop of wire L(Lgg l). Both loops are coplanar and their centres coincide at…
JEE Main 2022 — Physics Electromagnetism
2022mcqmedium
A small square loop of wire of side l is placed inside a large square loop of wire L(L≫l). Both loops are coplanar and their centres coincide at point O as shown in figure. The mutual inductance of the system is
Official previous-year question
Held on 25 Jul 2022 · Verified 6 Jul 2026.
Options
A
πl22μ0L2
B
22πLμ0l2
C
22πlμ0L2
D
πL22μ0l2
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Solution
Let a current, I pass through the square loop of side, L. The magnetic field at the centre O,
B=4×Magneticfieldduetoeachside
⇒B=4×4πμ0⋅L/2I(sin45∘+sin45∘)
⇒B=πL2μ0I(21+21)=πL22μ0I
Magnetic flux linked with the small square loop,
ϕ=BA=Bl2=πL22μ0Il2
Mutual inductance of the coil,
M=Iϕ=πL22μ0l2.
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