A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north-south direction. Null points are found on the axis of the magnet at $14\; cm$ from the centre of the magnet. The earth's magnetic field at the place is $0.36\; G$ and the angle of $dip$ is zero. What is the total magnetic field (in $G$) on the normal bisector of the magnet at the same distance as the null-point (i.e., $14 \;cm$) from the centre of the magnet? (At null points, field due to a magnet is equal and opposite to the horizontal component of earth's magnetic field.)

Vedclass pdf generator app on play store
Vedclass iOS app on app store

Earth's magnetic field at the given place, $H=0.36\, G$ The magnetic field at a distance $d$, on the axis of the magnet is given as:

$B_{1}=\frac{\mu_{0}}{4 \pi} \frac{2 M}{d^{3}}=H\dots(i)$

Where, $\mu_{0}=$ Permeability of free space

$M=$ Magnetic moment The magnetic field at the same distance $d$, on the equatorial line of the magnet is given as:

$B_{2}=\frac{\mu_{0} M}{4 \pi d^{3}}=\frac{H}{2}$ [Using equation $(i)$]

Total magnetic field, $B=B_{1}+B_{2}$ $=H+\frac{H}{2}$

$=0.36+0.18=0.54 \,G$

Hence, the magnetic field is $0.54 \,G$ in the direction of earth's magnetic field.

Similar Questions

Vibration magnetometer before use, should be set

Vibration magnetometer is used for comparing

A tangent galvanometer has a coil with $50$ $turns$ and radius equal to $4$ $cm$. A current of $0.1 $ $A$ is passing through it. The plane of the coil is set parallel to the earth's magnetic meridian. If the value of the earth's horizontal component of the magnetic field is $7 \times {10^{ - 5}}$ $tesla$ and  ${\mu _0} = 4\pi \times {10^{ - 7}}\, weber/amp \times m$, then the deflection in the galvanometer needle will be.....$^o$

The error in measuring the current with a tangent galvanometer is minimum when the deflection is about.....$^o$

To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because