A circular loop of radius R is carrying current iA. The ratio of magnetic field at the centre of circular loop and at a distance R from the center of…
JEE Main 2023 — Physics Electromagnetism
2023mcqmedium
A circular loop of radius R is carrying current iA. The ratio of magnetic field at the centre of circular loop and at a distance R from the center of the loop on its axis is :
Official previous-year question
Held on 24 Jan 2023 · Verified 6 Jul 2026.
Options
A
1:32
B
32:2
C
22:1
D
1:2
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Solution
The magnitude of magnetic field at the centre of loop is
B1 =Bcentre =2Rμ∘i…(1)
The magnitude of magnetic field at a point at a distance x from the centre along axis of loop is
Baxis =2(R2+x2)23μ∘iR2
B2 =2(223)R3μ∘iR2…(2)(sincex=R)
Dividing equation 1 by equation 2, we get
B2B1=22:1
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