1. Resistors Colour Code SI Units

2. 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

3. Resistors Resistance and tolerance value determined by coloured bands on resistor Power rating determined by size or composition of resistor Schematic symbols:

4. Resistor Types Fixed value Variable –Rheostat - two terminals, one fixed, one sliding –Potentiometer - three terminals, two fixed, one sliding

5. Colour Codes

6. Value = ?

7. Scientific Notation

8. SI Units: IEEE adopted the International System of Units in 1965 proposed in France 1960 (Systeme International d’Unites) QuantitySI Base UnitUnit Symbol length/distancemeterm massgramg timesecondsec electric currentampereA elec potential diff.voltV elec resistanceohm  elec powerwattW

9. SI Unit Prefixes: PrefixFactor by which the base unit is MultipliedLetter Symbol exa1 000 000 000 000 000 000 = 10 18 E peta1 000 000 000 000 000 = 10 15 P tera1 000 000 000 000 = 10 12 T giga1 000 000 000 = 10 9 G mega1 000 000 = 10 6 M kilo1 000 = 10 3 k hecto1 00 = 10 2 h deka1 0 = 10 1 da Base Unit1 deci0.1 = 10 -1 d centi0.01 = 10 -2 c milli0.001 = 10 -3 m micro0.000 001 = 10 -6  nano0.000 000 001 = 10 -9 n pico0.000 000 000 001 = 10 -12 p femto0.000 000 000 000 001 = 10 -15 f atto0.000 000 000 000 000 001 = 10 -18 a

10. 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.

11. 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 = 2 10 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 (10 6 ) bytes. Precisely 1 kB x 1 kB = 1024 x 1024 = 2 10 x 2 10 = 2 20 = 1048576 bytes. gegabyte - GB or G-byte - represents about 1 billion (10 9 ) bytes. Precisely 1 kB x 1 kB x 1 kB = 1024 x 1024 x 1024 = 2 10 x 2 10 x 2 10 = 2 30 = 1073741824 bytes. terebyte - TB or T-byte - represents 1 about trillion (10 12 ) bytes. Precisely 1 kB x 1 kB x 1 kB x 1 kB = 1024 x 1024 x 1024 x 1024 = 2 10 x 2 10 x 2 10 x 2 10 = 2 40 = 1099511627776 bytes.