APPENDIX. 



DIMENSIONS OF PHYSICAL QUANTITIES. 



L = length; M =: mass ; T : time. 



Quantity. 



Area. 



Volume. 



Mass. 



Density. 



Velocity. 



Acceleration. 



Angle. 



Angular Velocity. [T-'] 



Quantity. Dimensions. 



Momentum. [L ^I T~'] 



Moment of Inertia. [M L'^] 



Force. [L M T"'] 



Stress (per unit area). [L,"' M T"'] 



Work or Energy. [v M T-'] 



Rate of Working. [V M T-'] 



Heat. [L'''MT-^J 

 Thermal Conductivity. [L"' M T-'] 



In Electrostatics. 



Quantity of Electricit}-. 



Surface Density : quantity per unit area. 



Difference of Potential: quantity of work required 

 to move a quantity of electricity ; (work done) -=- (quan- 

 tity moved). 



Electric Force, or Electro-motive Intensity: 



(quantity) h- (distance'-*). 

 Capacity of an accumulator: e-^E. 

 Specific Inductive Capacity. 



In Magnetics. 



Quantity of Magnetism, or Strength of Pole. 



Strength or Intensity of Field: 



(quantity) ~- (distance''). 

 Magnetic Force. 

 Magnetic Moment: (quantity) x (length). 



Intensity of Magnetization: magnetic moment per 



unit volume. 

 Magnetic Potential: work done in moving a quantity 



of magnetism ; (work done) -h (quantity moved). 

 Magnetic Inductive Capacity. 



Symbol. 



E 



Dimensions in 

 electrostatic system. 



[L^ m' T-'] 

 [I/^ M^ T-'] 

 \\} M^ T-'] 



[Iv 



-\ M* T" 



C" or ^ 

 k 



[L] 

 [0] 



Dimensions in 



electro-magnetic 



system. 



[L-^ M^ T-'] 

 [L"^ M^ T-'] 



[I.-' M^ T-"] 



[ij m" t-'] 



[l/i M^ T-'] 

 VorVL [I/'m^T^-J 

 /A [0] 



in 

 S 



tn I 

 I 



In Electro-magnetics. Symbol. 



Intensity of Current. i 



Quantity of Electricity convej'cd ])y cur- e 



rent : (intensity) x (time). 



Potential, or difference of potential : (work 

 done) -§- quantit}' of electricity upon which 

 work is done. 



Electric Force: the mechanical force act- 

 ing on electro-magnetic unit of quantity ; 

 (mechanical force) -:- (quantity). 



Resistance of a conductor: E ^- i. R 



Capacity : quantity of electricity stored up q 



per unit potential-difference produced by it. 

 Specific Conductivity: the intensity of 



current passing across unit area under the 



action of unit electric force. 

 Specific Resistance: the reciprocal of r 



specific conductivity. 



Dimensions in 



electro-magnetic 



system. 



[L= M^ T-'] 

 [l.^ m'j 



E \xr- M^ T-^] 

 ?£ [lyi M^ T-*] 



[I.T-'l 

 [L- T'] 



[L--' T] 



Name of 

 practical unit. 



Ampere. 

 Coulomb. 



Volt. 



Ohm. 

 Farad. 



J 



Smithsonian Tadles, 



262 



