JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Magnetic Effects of Current

Two identical small bar magnets each of dipole moment

35 J / T

are placed at a center to center separation of 10 cm , with their axes perpendicular to each other as shown in figure. The value of magnetic field at the point P midway between the magnets is

α \times 1 0^{- 3} T

. The value of

α

is ______ .
(

μ_{0} = 4 π \times 1 0^{- 7} Tm / A

)

Answer: 12

Solution

At P each magnet is a distance

r = 5 cm = 0.05 m

away. Point P lies on the axis of one magnet, giving

B_{1} = \frac{μ _{0}}{4 π} \frac{2 M}{r ^{3}}

, and on the equatorial line of the other, giving

B_{2} = \frac{μ _{0}}{4 π} \frac{M}{r ^{3}}

; because the axes are perpendicular, these two fields are mutually perpendicular. Hence

B = B_{1}^{2} + B_{2}^{2} = \frac{μ _{0} M}{4 π r ^{3}} 5 = \frac{1 0 ^{- 7} \times 3 5 \times 5}{( 0.05 ) ^{3}} = \frac{15 \times 1 0 ^{- 7}}{1.25 \times 1 0 ^{- 4}} = 12 \times 1 0^{- 3} T .

The value of

α

12

JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Integer answer

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JEE Main · 2026 · 04 Apr 2026 · Shift 2 · Magnetic Effects of Current

Solution

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