Magnetic field intensity is defined as:
A. Magnetic moment per unit volume
B. Magnetic induction force acting on a unit magnetic pole
C. Number of lines of force crossing per unit area
D. Number of lines of force crossing a unit volume

Hint: The given question requires us to define magnetic field intensity and choose the most appropriate option that describes its meaning. There are various definitions of the term ‘Magnetic field intensity’ and we have to choose one from the options provided to us in the problem itself.

Complete answer:
Magnetic field intensity is the part of the magnetic field in a material that arises from an external source of current and is not an intrinsic property of the material itself. It is a vector quantity denoted by the symbol H. The unit for measurement of magnetic field intensity is amperes per meter.

The Magnetic Field Intensity or Magnetic Field Strength is a ratio of the magnetomotive force needed to create a certain Flux Density within a particular material per unit length of that material.In other words, Magnetic field intensity is the magnetic induction force acting on a unit magnetic pole.

So, the correct answer is option B.

Note: We must know the theoretical meaning of magnetic moment and magnetic induction to solve such questions. We must have visualized the meaning of magnetic field intensity as magnetic induction force acting on a unit magnetic pole. All these terms are very closely linked to each other so we should be careful while using the terms.