xxxii INTRODUCTION. 



Magnetic Pole Strength or Quantity of Magnetism has already been shown 

 to have the dimensional formula [_M^DT~^fx^^. 



Magnetic Flux characterizes the magnetized state of a magnetic circuit. 

 Through a surface inclosing a magnetic pole it is proportional to the magnetic 

 pole strength. The dimensional formula is that for magnetic pole strength. 



Magnetic Field Intensity or Magnetizing Force is the ratio of the force on a 

 magnetic pole placed at the point and the magnetic pole strength. The dimen- 

 sional formula is therefore the ratio of the formulae for a force and magnetic 

 quantity, or iMLT-^/MiDT-'/x^^ or [M^L-^T^V"^]- 



Magnetic Potential or Magnetomotive Force at a point is measured by the 

 work which is required to bring unit quantity of positive magnetism from zero 

 potential to the point. The dimensional formula is the ratio of the formulae for 

 work and magnetic quantity, iMr-T-yM^DT-'fj.'^ or IM^L'T-'/jT'J 



Magnetic Moment is the product of the pole strength by the length of the 

 magnet. The dimensional formula is [^M^V^T~^fx^']. 



Intensity of Magnetization of any portion of a magnetized body is the ratio 

 of the magnetic moment of that portion and its volume. The dimensional 

 formula is lAI^DT-'ii^/U^ or [MiL-iT^ijU']- 



Magnetic Induction is the magnetic flux per unit of area taken perpendicular 

 to the direction of the magnetic flux. The dimensional formula is [ilf »L' J^^^t V^"3 

 or [i/iL-^r-i/x^]. 



Magnetic Susceptibility is the ratio of intensity of magnetization produced 

 and the intensity of the magnetic field producing it. The dimensional formula 

 is [MiL-ir-iMV^*^~^^"'M~^] or [//]. 



Current, /, flowing in circle, radius r, creates magnetic field at its center, 

 27r//r. Dimensional formula is product of formulae for magnetic field intensity 

 and length or iM^LiT-'fJL-'J 



Quantity of Electricity is the product of the current and time. The dimen- 

 sional formula is [M *LV~^]- 



Electric Potential, or Electromotive Force, as in the electrostatic system, is 

 the ratio of work to quantity of electricity. The dimensional formula is [ML-r-y 

 ilfiLV-*] or [MiL'r-V^]- 



Electrostatic Capacity is the ratio of quantity of electricity to difference of 

 potential. The dimensional formula is [L~^rV~^]- 



Resistance of a Conductor is the ratio of the difference of potential be- 

 tween its ends and the constant current flowing. The dimensional formula is 

 iM^V^T-^fx^/M^DT-'iJL-^^ or lLT-'ff\' 



Conductance is the reciprocal of resistance, and the dimensional formula is 



[l-^Tm-^]. 



Conductivity is the quantity of electricity transmitted per unit area per unit 

 potential gradient per unit of time. The dimensional formula is [ilf^L*/!"*/ 

 U{MiLiT-^fj,i/L) r] or [I'^r^-i]. 



