The greatest power of using this notation comes when you have to multiply or divide these very large or very small numbers. These procedures are shown below. It often happens that the standard units for some quantity is not convenient in a particular case. There is an established series of values of resistors, only values with certain digits are manufactured. Tolerance of the resistance varies - resistors are mass manufactured, so some variations are hard to avoid.
Resistors generate heat.
Resistors have a wattage rating. Wire wound resistors have their value written on them. The Resistor Colour Code allows to read the values of resistors. The procedure is as follows. You should ignore the colour of the resistor body.