what does this mean?

ΦB

 

Hello,

It could be "magnetic flux".

Bertus

 

what does this mean?

ΦB

What is the context? Where do you see this filter?

From Wikipedia:

The lower-case letter φ (or often its variant, ϕ) is often used to represent the following:

• The golden ratio
  
  1.618033988749894848204586834... in mathematics, art, and architecture.
• Euler's totient function φ(n) in number theory; also called Euler's phi function.
• The cyclotomic polynomial functions Φn(x) of algebra.
• In algebra, group or ring homomorphisms
• In probability theory, ϕ(x) = (2π)−½e−x2/2 is the probability density function of the normal distribution.
• In probability theory, φX(t) = E[eitX] is the characteristic function of a random variable X.
• An angle, typically the second angle mentioned, after θ (theta). Especially:
  • The argument of a complex number.
  • The phase of a wave in signal processing.
  • In spherical coordinates, mathematicians usually refer to phi as the polar angle (from the z-axis). The convention in physics is to use phi as the azimuthal angle (from the x-axis).
  • One of the dihedral angles in the backbones of proteins in a Ramachandran plot
  • Internal or effective angle of friction.
• The work function of a surface, in solid-state physics.
• A shorthand representation for an aromatic functional group in organic chemistry.
• The fugacity coefficient in thermodynamics.
• The ratio of free energy destabilizations of protein mutants in phi value analysis.
• In cartography and navigation, latitude.
• In combustion engineering, fuel–air equivalence ratio. The ratio between the actual fuel air ratio to the stoichiometric fuel air ratio.
• A sentence in first-order logic.
• The Veblen function in set theory
• Porosity in geology and hydrology.
• Strength (or resistance) reduction factor in structural engineering, used to account for statistical variabilities in materials and construction methods.
• The symbol for a voiceless bilabial fricative in the International Phonetic Alphabet (using the straight line variant character)
• In economics, this is usually an additive term.[clarification needed]
• In flight dynamics, the roll angle.
• In philosophy, φ is often used as shorthand for a generic act. (Also in upper-case.)
• In perceptual psychology, the phi phenomenon is the apparent motion caused by the successive viewing of stationary objects, such as the frames of a motion picture.

The upper-case letter Φ is used as a symbol for:

• The golden ratio conjugate −0.618... in mathematics.
• The magnetic flux and electric flux in physics, with subscripts distinguishing the two.
• The cumulative distribution function of the normal distribution in mathematics and statistics.
• In philosophy, Φ is often used as shorthand for a generic act. (Also in lower-case.)[citation needed]
• The number of phases in a power system in electrical engineering, for example 1Φ for single phase, 3Φ for three phase.
• A common symbol for the parametrization of a surface in vector calculus.
• In Lacanian algebra, Φ stands for the imaginary phallus and also represents phallic signification; -Φ stands in for castration.[4]

The diameter symbol in engineering, ⌀, is often incorrectly referred to as "phi". This symbol is used to indicate the diameter of a circular section; for example, "⌀14" means the diameter of the circle is 14 units.

I would expect in this case it is denoting magnetic flux because the symbol is often paired with a "B" in those cases (though most often it is a subscript):

More wikipedia: https://en.wikipedia.org/wiki/Magnetic_flux

EDIT: Bertus, you beat me to it!

 

Towards the bottom.

http://physics.info/inductance/

That's what I was thinking. I just wanted to make sure though the equation following it may come in handy so I wanted to know.

Thank you both!!
Ziggey