Magnetic field due to a bar magnet 2 cm long having a pole strength of 100 Am at a point 10 cm from each pole is

Question

Magnetic field due to a bar magnet 2 cm long having a pole strength of 100 Am at a point 10 cm from each pole is (A) 2×10-4 T (B) 8π ×10-4 T (C) 2×10-5 T (D) 4×10-4 T

Tardigrade Admin · Accepted Answer

Magnetic field at a point on equatorial line of a bar magnet is given by, B =

\frac{μ _{0}}{4 π} \frac{M}{( r ^{2} + l ^{2} ) ^{3/2}}

Here, M =

m \times 2 l = (100 \times 2 \times 1 0^{- 2})

and

(r^{2} + l^{2})^{1/2} = (10 \times 1 0^{- 2})

∴

B =

\frac{1 0 ^{- 7} \times 100 \times 2 \times 1 0 ^{- 2}}{( 10 \times 1 0 ^{- 2} ) ^{3}} = 2 \times 1 0^{- 4}

T

Q. Magnetic field due to a bar magnet 2 cm long having a pole strength of 100 Am at a point 10 cm from each pole is

$2 \times 1 0^{- 4} T$

$8 π \times 1 0^{- 4} T$

$2 \times 1 0^{- 5} T$

$4 \times 1 0^{- 4} T$

Q. Magnetic field due to a bar magnet 2 cm long having a pole strength of 100 Am at a point 10 cm from each pole is

2×10−4T

8π×10−4T

2×10−5T

4×10−4T

Magnetic field at a point on equatorial line of a bar magnet is given by, B = 4πμ0​​(r2+l2)3/2M​ Here, M = m×2l=(100×2×10−2) and (r2+l2)1/2=(10×10−2) ∴ B = (10×10−2)310−7×100×2×10−2​=2×10−4 T

$2 \times 1 0^{- 4} T$

$8 π \times 1 0^{- 4} T$

$2 \times 1 0^{- 5} T$

$4 \times 1 0^{- 4} T$