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The magnetic field at the centre of a current carrying circular loop of radius R is 16 μT. The magnetic field at a distance x=√3R on its axis from the centre is ______ μT.

Asked in JEE Main 28th Jan 1st Shift 2026 · Centre and axis of a loop

• (1) 8
• (2) 4
• (3) 2√2
• (4) 2

Step-by-step solution

Why the other options are wrong

• (1) Uses power 1: B∝R/(√R²+x²)
• (2) Uses (R/r)² instead of (R/r)³
• (3) Mis-evaluates (R²+x²)^3/2=(4R²)^3/2 as 4√2R³ instead of 8R³

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