Ballistic Galvanometer
ASSIGNMENT: Ballistic Galvanometer
Name: Faisal Ahmed Moshiur
Group: A Batch: 10
Roll: Sh-099
Introduction
The basic theory on a ballistic galvanometer starts with torque associated with a current carrying loop. A brief review of ordinary moving coil galvanometer is presented followed by the effects of transient currents. This paves the way for a detailed analysis of ballistic galvanometer.
Torque on a Current Loop
It is well known that a current loop behaves like a magnetic dipole. The magnitude of the magnetic moment, associated with a current loop, equals the product of the area of the loop and the current flowing through it. Its direction is normal to the plane of the loop and is along the direction of advancement of a right handed screw rotated in the sense of current flow in the loop.
It follows that for a current loop of area A, carrying an anticlockwise current of magnitude I, the equivalent magnetic moment is
where is a unit vector normal to the plane of the loop (taken as the plane of the paper here) and directed outwards.
If the same loop were to carry a clockwise current, the direction of would be along the inward directed normal to the plane of the paper.
For a loop having n turns, each of area A, the magnitude of its associated magnetic moment would become (n A) I.
When this loop is present in the region of a uniform magnetic field , it would experience a torque where, The magnetic torque tries to align the magnetic moment vector in the direction of magnetic field. Thus, combining the above facts, we have, , where θ is the angle between the directions of and.
For a loop, having its plane parallel to the direction of , θ equals . Hence the torque, on the current loop in such a case, would have a
Name: Faisal Ahmed Moshiur
Group: A Batch: 10
Roll: Sh-099
Introduction
The basic theory on a ballistic galvanometer starts with torque associated with a current carrying loop. A brief review of ordinary moving coil galvanometer is presented followed by the effects of transient currents. This paves the way for a detailed analysis of ballistic galvanometer.
Torque on a Current Loop
It is well known that a current loop behaves like a magnetic dipole. The magnitude of the magnetic moment, associated with a current loop, equals the product of the area of the loop and the current flowing through it. Its direction is normal to the plane of the loop and is along the direction of advancement of a right handed screw rotated in the sense of current flow in the loop.
It follows that for a current loop of area A, carrying an anticlockwise current of magnitude I, the equivalent magnetic moment is
where is a unit vector normal to the plane of the loop (taken as the plane of the paper here) and directed outwards.
If the same loop were to carry a clockwise current, the direction of would be along the inward directed normal to the plane of the paper.
For a loop having n turns, each of area A, the magnitude of its associated magnetic moment would become (n A) I.
When this loop is present in the region of a uniform magnetic field , it would experience a torque where, The magnetic torque tries to align the magnetic moment vector in the direction of magnetic field. Thus, combining the above facts, we have, , where θ is the angle between the directions of and.
For a loop, having its plane parallel to the direction of , θ equals . Hence the torque, on the current loop in such a case, would have a
References: 1. Books: Principles of Electromagnetics by Matthew N. O. Sadiku, Oxford University Press Introduction to Electrodynamics by David J. Griffiths, Pearson Education Electricity and Magnetism by D. L. Sehgal, K. L. Chopra, N. K. Sehgal, Pub: Sultan Chand and sons Electricity and Magnetism by E. M. Purcell, Berkeley Physics Course, Pub: Mc Graw Hill Science 2. Internet: spiff.rit.edu/classes/phys313/lectures/magwire/magwire_f01_long.html wikipedia.org