পাতা:মোটর শিক্ষক - শৈলজাপ্রসাদ দত্ত.pdf/৩৪৯

DEFINITIONS OF UNITS. (FROM SMITHSONIAN TABLES.) ACTIVITY. Power of rate of doing work; unit, the Watt, AMPERE. Unit of electrical current. The, inter-, national ampere, “which is one-tenth of the unit of current of the C. G. S. system of electromagnetic units, and which is represented sufficiently well for practical use by the unvarying currett which, when passed through a solution of nitratic of silver in water, and in accordance with accompanying specificagons, deposits silver at the rate of o'ool i 18oo of a gram per second.” The ampere = I coulomb per seconda, volt across 1 ohm = Io E. M. U. = 3x Io“ E. S. U. ( E. M. R. as C. G. S. electromagnetic units. E. S. Us C. G. S. electrostatic urits). Ampeses se voltslohms = watts/volts. Amperes x volts - ampereso X ohms = watts. ANGSTORM. Unit of wave-length - to meter. ATMOSPHERE. Unit of pressure. English normal = 14 pounds per sq. in s 29929 in. as 76o 18 mm. Hg. 32ʻF. French normal sa 76o mm of Hg. O°C as 29"922 in. ar I47olbs. per sq. in. BAR. A pressure of one dyne per cmo. BRITISH THERMAL UNIT. Heat required to raise one pound of water at its temperature of maximum density, I'F. s. 252 gram-calories. CALORIE. Small calorie- gram-caloriéa therm = quantity of heat required to raise one gram of water at its maximum density, one degree Centigrade.