1 Basic Elements I

1 Basic Elements I - ELEC 101 Basic Elements 1 2010/11...

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Unformatted text preview: ELEC 101 Basic Elements 1 2010/11 Spring Fundamentals 1 Systeme international d’unites = metric units or MKS units (as opposed to CGS units) SI unit ELEC 101 Basic Elements 2 2010/11 Spring Derived quantities – conversion and equivalence of units • A l l derived units can be expressed as combination of the fundamental units • Derived units are based on specific equations. Examples: F = ma Newton = Kg x m/s 2 C = Q/V Farad = Coulomb / Volt F = A 2 ‐ s 2 /J V = IR Volt = Ampere ‐ Ohm = J/A 2 ‐ s • Different equations involving the same quantity should yield the same results. Examples: Work done = Energy = Force x distance J = Kg x m/s 2 x m E = mc 2 J = Kg x (m/s) 2 , same as above • E l e c t r i c current is given in Ampere (A): I = Q/s Ampere = Coul/s • E l e c t r i c potential is given in Volt (V): Power = VxI Volt = J/A ‐ s ELEC 101 Basic Elements 3 2010/11 Spring Important unit – Hertz • H e r t z is a unit for frequency (symbol ). 1 Hz = 1 cycles per second • P e r i o d : time for one cycle T = 1 / • 1 Hz corresponds to a period of 1 s • H z is not to be confused with radian/s (angular frequency ) • 1 cycle = 2 radian • E x a m p l e : Fastest CPU in 2010 is IBM z196 with a 5.2 GHz clock rate • Corresponding period = 1 / 5.2x10 9 = 0.19 ns t 2 t 2 sin sin T ELEC 101 Basic Elements 4 2010/11 Spring Prefixes in SI system ELEC 101 Basic Elements 5 2010/11 Spring Examples 1 nm = 10-9 m = 10 Å 1 Å = 10 10 m (Å = Angstrom) 1 fA = 10-15 A 1 pF = 10-12 F 1 ns = 10-9 s 1 MHz = 10 6 Hz 1 GB = 1 gigabyte = 10 9 Byte Radius of an atom = few Å ELEC 101 Basic Elements 6 2010/11 Spring Chinese large units and prefixes Prefix Unit Examples 10 3 kilo thousand km, kHz (why lower case?) 10 6 mega million MHz, M$ is more scientific 10 9 giga billion GB, GHz 10 12 tera trillion TW, THz 10 15 peta quadrillion PHz In Chinese, prefix and unit are the same word. Jumps in steps of 10 4 10 3 千 10 4 萬 萬事勝意 10 8 億 億元(億萬富翁 is wrong language! ) 10 12 兆 兆赫= MHz!!! Confusing 10 16 京 10 20 垓( gai ) 10 24 秭( zi ) 10 28 穰( rang ) ELEC 101 Basic Elements 7 2010/11 Spring More on Chinese units (not in exam) • 《孫子算經》:凡大數之法,萬萬曰億,萬億曰兆,萬兆曰京,萬京曰垓, 萬垓曰秭,萬秭曰穰,萬穰曰溝,萬溝曰澗,萬澗曰正,萬正曰載。 • 公元263年劉徽在開方不盡時用十進小數(微數)表示無理根的近似值, 開十進分數之先河。古代用厘、毫、絲、秒、忽表示分以下的奇零部分。 • While there are Chinese terms for large numbers, for small numbers, there is none beyond 10 ‐ 6 . Thus one can simply use translations of the SI system 10 ‐ 3 milli 毫 毫秒,毫升,毫米,毫伏,毫安 10 ‐ 6 micro 微 微秒,微升,微米,微伏,微安 10 ‐...
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1 Basic Elements I - ELEC 101 Basic Elements 1 2010/11...

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