The reduction factor K of a tangent galvanometer is written on the instrument. The manual says that the current is obtained by multiplying this factor to tan θ. The procedure works well at Bhuwaneshwar. Will the procedure work if the instrument is taken to Nepal? If there is some error, can it be corrected by correcting the manual or the instrument will have to be taken back to the factory?
Yes. The procedure will work if it is taken to Nepal as well.
The tangent Galvanometer is used to find out current or earth’s magnetic field. It works on the equation,
Where B is a known magnetic field produced, BH is the horizontal component of geomagnetic field, and θ is the angle shown in the galvanometer dial.
As the magnetic field, B is produced by the current passing through a loop according to Ampere’s law, is,
Where n is the number of loops, i is the current and r is the radius of the loop.
Substituting this in eqn.1, we can rearrange it to find tan θ as,
Also,
Where k is the reduction factor and is a constant. So, by correcting the data for k and the value of tanθ, the measurements can be accurately conducted.
So, despite the place, we can calculate the current depending on the tanθ value. So, any error caused can be rectified by the angle corrections and there is no need to bring the instrument back to the factory.