Question

A short bar magnet with its north pole facing north forms a neutral point at P in the horizontal plane. It the magnet is rotated by 90⁰ in the horizontal plane, the net magnetic induction at P is : (Horizontal component of earth's magnetic field = B_H)

• A. 0
• B. $2 B _ { H }$
• C. $\frac { \sqrt { 5 } } { 2 } B _ { H }$
• D. $\sqrt { 5 } B _ { H }$

Answer 1

Answer: (D)

$\sqrt { 5 } B _ { H }$

Answer 2

Initially

Neutral point is obtained on equatorial line and at neutral point $\left| B _ { H } \right| \neq B _ { e } \mid$

Where $B _ { H } =$ Horizontal component of earth's magnetic field and $B e =$Magnetic field due to bar magnet on it's equatorial line

Finally Point P comes on axial line of the magnet and at P, net magnetic field