Initial Concepts
Production of a Magnetic Field 
When an electron travels along a wire, a magnetic field is produced around the electron (Fig 1).Hydrogen Protons 
It is necessary to have a source of hydrogen pro- tons (protons in the nuclei of hydrogen atoms, which are associated with fat and water mol ecules) in order to form our MR signal  The hydrogen proton is positively charged and spins about its axis (like a child's spinning top).Main Magnetic Field
The main magnetic field of an MR system comes from a large electric current flowing through wires that are formed into a loop in the magnet of the imaging system (Fig 3).The wires are immersed in liquid helium (at superconducting temperatures) so that very large currents can be used to produce the strong magnetic field.When an electric current flows in a wire that is formed into a loop, a large magnetic field will be formed perpendicular to the loop 
Resonance
 Resonance aids an efficient transfer of energy.This positively charged spinning proton acts like a tiny magnet (Fig 2).