Magnetic Field Strength (H) gives the quantitative measure of strongness or weakness of the magnetic field.
H = B/μo
B = Magnetic Flux Density
μo = Vacuum Permeability
The magnetic Field strength at the center of circular loop carrying current I is given by
B = μoI/2r
B/μo = I/2r
H = I/2r At/m
Where r = Radius
Neon-lamp holders A lot of industrial electronic equipment uses neon lamps to indicate when they have been energized from the mains. If the lamp fails to glow, it means something is wrong with the supply circuit, the equipment, or the indicator itself. The neon lamps used are quite small and housed in holders 5 mm to 10 mm in diameter.
Ampere works law or Circuital Law
This law relates to work done in a magnetic circuit i.e. closed magnetic flux path.
The work done on or by a unit N-pole in moving once round any complete path is equal to the product of current and number of turns enclosed by that path