A resistor is a component that resists the flow of electricity. With the same terminal voltage across resistor, the larger resistance, the lower current flow.

There are DIP type resistor and SMD type resistor (figure from internet). The larger body size of the same resistance, the higher power rating. The popular power rating of DIP type resistor is 1/8W,1/4W,1/2W,1W etc. and the popular size of SMD type resistor is 0201,0402,0603,0805,1206,1210 etc.

The behavior of a resistor is dictated by the relationship specified by Ohm’s law : I (current)=V (voltage) / R (resistance).

Ohm’s law states that the voltage (V) across a resistor is proportional to the current (I), where the constant of proportionality is the resistance (R)

Unit : K = 1000, m=1/1000(=0.001)

1K Ohm resistor = 1000 Ohm

Example :

10V is applied to a 1K ohm resistor, the current flow though this resistor is 10 volt / 1000 ohm = 0.01A = 10mA.