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Resistors Colour Code SI Units. Resistors. Used to limit amount of current in circuit There must always be some resistance in a circuit. Three properties of resistors: resistance value tolerance power rating. Resistors.
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Resistors Colour Code SI Units
Resistors • Used to limit amount of current in circuit • There must always be some resistance in a circuit. • Three properties of resistors: • resistance value • tolerance • power rating
Resistors • Resistance and tolerance value determined by coloured bands on resistor • Power rating determined by size or composition of resistor • Schematic symbols:
Resistor Types • Fixed value • Variable • Rheostat - two terminals, one fixed, one sliding • Potentiometer - three terminals, two fixed, one sliding
Colour Codes Value = ?
SI Units: • IEEE adopted the International System of Units in 1965 proposed in France 1960 (Systeme International d’Unites) Quantity SI Base Unit Unit Symbol length/distance meter m mass gram g time second sec electric current ampere A elec potential diff. volt V elec resistance ohm elec power watt W
SI Unit Prefixes: Prefix Factor by which the base unit is Multiplied Letter Symbol exa 1 000 000 000 000 000 000 = 1018 E peta 1 000 000 000 000 000 = 1015 P tera 1 000 000 000 000 = 1012 T giga 1 000 000 000 = 109 G mega 1 000 000 = 106 M kilo 1 000 = 103 k hecto 1 00 = 102 h deka 1 0 = 101 da Base Unit 1 deci 0.1 = 10-1 d centi 0.01 = 10-2 c milli 0.001 = 10-3 m micro 0.000 001 = 10-6 nano 0.000 000 001 = 10-9 n pico 0.000 000 000 001 = 10-12 p femto 0.000 000 000 000 001 = 10-15 f atto 0.000 000 000 000 000 001 = 10-18 a
bits and Bytes • bit - short for binary digit. In binary system a bit can be either 0 or 1. • Byte - In order to represent numbers, letters, and special characters, bits are combined into groups of eight bits called bytes. Each byte typically represents one character - in many computers, one addressable storage location. The capacity of main memory is expressed in numbers of bytes.
commonly used units There are four commonly used units of measurement to describe memory capacity: • kilobyte - abbreviated k, kB, or k-byte - is equivalent to approximately 1000 bytes. (More precisely, 1kB = 1024 bytes = 210 bytes. The older IBM PCs had a top capacity of 640KB, or about 640,000 characters of data. • megabyte - MB or M-byte - represents about 1 million (106) bytes. Precisely 1 kB x 1 kB = 1024 x 1024 = 210 x 210 = 220 = 1048576 bytes. • gegabyte - GB or G-byte - represents about 1 billion (109) bytes. Precisely 1 kB x 1 kB x 1 kB = 1024 x 1024 x 1024 = 210 x 210 x 210 = 230 = 1073741824 bytes. • terebyte - TB or T-byte - represents 1 about trillion (1012) bytes. Precisely 1 kB x 1 kB x 1 kB x 1 kB = 1024 x 1024 x 1024 x 1024 = 210 x 210 x 210 x 210 = 240 = 1099511627776 bytes.