Question 69: Magnetism and Matter

Question

A bar magnet of length 14 cm is placed in the magnetic meridian with its north pole pointing towards the geographic north pole. A neutral point is obtained at a distance of 18 cm from the center of the magnet. If BH = 0.4 G, the magnetic moment of the magnet is : (1G = 10$$-$$4 T)

Accepted Answer

$$B = 2{B_0}\sin 	heta $$
$$B = 2{{{\mu _0}} \over {4\pi }}{m \over {{r^2}}} 	imes {7 \over r}$$
$$ \Rightarrow 0.4 	imes {10^{ - 4}} = 2 	imes {10^{ - 7}} 	imes {{m 	imes 7} \over {{{({7^2} + {{18}^2})}^{3/2}}}} 	imes {10^4}$$
$$ 	herefore $$ $$m = {{4 	imes {{10}^{ - 2}} 	imes {{(373)}^{3/2}}} \over {14}}$$
$$ \Rightarrow $$ M = m $$	imes$$ 14 cm = $$ = m 	imes {{14} \over {100}}$$
$$ \Rightarrow $$ $$M = {{0.04 	imes {{(373)}^{3/2}}} \over {14}} 	imes {{14} \over {100}}$$
$$ \Rightarrow $$ M = 2.880 J/T

Answer

2.880 $$	imes$$ 102 J T$$-$$1

Answer

2.880 J T$$-$$1

Answer

2.880 $$	imes$$ 103 J T$$-$$1

Answer

28.80 J T$$-$$1

Magnetism and Matter

A bar magnet of length 14 cm is placed in the magnetic meridian with its north pole pointing towards the geographic north pole. A neutral point is obtained at a distance of 18 cm from the center of the magnet. If BH = 0.4 G, the magnetic moment of the magnet is : (1G = 10$-$4 T)

Choose the correct answer: