Why we take magnetic needle small in deflection magnetometer?
Answers
Deflection magnetometer, box-type vibration magnetometer, timer, bar magnet.The deflection magnetometer consists of a large compass box with a small magnetic needle pivoted at the center of a circular scale so that the needle is free to rotate in a horizontal plane .
A large aluminium pointer is rigidly fixed perpendicular to the magnetic needle. The circular scale is graduated in degrees. (0-0) and (90-90) readings are marked at the ends of two perpendicular diameters. The compass box is placed at the center of a wooden board one meter long. The wooden board has a millimeter scale along its axis. The zero of this scale is at the center of the compass box.
The box-type vibration magnetometer consists of a rectangular box with glass sides. A vertical tube is fitted at the top and a torsion-free fiber is suspended from the top of this tube carries a light aluminum stirrup in the box below. The bar magnet can be placed horizontally in this stirrup. At the bottom of the box two leveling screws are provided .
Theory
The horizontal component of earth's magnetic field, BH, is the component of the magnetic field of the earth along a horizontal plane whose normal vector passes through the center of the earth. BH is measured in Tesla, T.
The magnetic dipole moment m of a magnetic dipole is the property of the dipole which tends to align the dipole parallel to an external magnetic field. m is measured in Ampere-square meters (A m2) or, equivalently, in Joules per Tesla (J/T).