Question

Two points $A$ and $B$ are situated at a distance $x$ and $2x$ respectively from the nearer pole of a magnet $2cm$ long. The ratio of magnetic field at $A$ and $B$ is

• A. $4:1$ exactly
• B. $4:1$ approximately
• C. $8:1$ approximately
• D. $1:1$ approximately

Answer 1

The correct option is C $8:1$ approximately

Taking the distance from the center of the magnet,

$\frac{B_1}{B_2}={\left[\frac{x_2}{x_1}\right]}^3={\left(\frac{2x+1}{x+1}\right)}^3=\frac{8}{1}$ Approximately