Resistors

Meaning of Resistor

A resistor restricts the flow of current, for example to limit the current passing through an LED. A resistor is used with a capacitor in a timing circuit.

Types of Resistors

1. Rheostat

This type of variable resistor with 2 contacts (a rheostat) is usually used to control current. Examples include: adjusting lamp brightness, adjusting motor speed, and adjusting the rate of flow of charge into a capacitor in a timing circuit.

2. Potentiometer

This type of variable resistor with 3 contacts (a potentiometer) is usually used to control voltage. It can be used like this as a transducer converting position (angle of the control spindle) to an electrical signal.

3. Variable resistor  (Preset)

This type of variable resistor (a preset) is operated with a small screwdriver or similar tool. It is designed to be set when the circuit is made and then left without further adjustment. Presets are cheaper than normal variable resistors so they are often used in projects to reduce the cost.

4. Fixed Resistor

Fixed resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.

5. LDR

The Light Dependent Resistor (LDR) is one of the most widely used and preferred photo resistor in most projects that requires the use of a photosensor. The most ideal characteristic it carries is that it is cheap and rugged. This means it can be used in multiple projects. Also, as the name of LDR denotes, their resistance to electricity depends on the intensity of light shining on them. It can thus be said that their resistance is inversely proportional to the amount of light they receive. LDR are therefore the most preferred photosensors, whereby a varying amount of light intensity is expected, as opposed to a light intensity that is fixed.

6. Thermistor

Thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiter, temperature sensors (Negative Temperature Coefficient or NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements. that is Positive Temperature Coefficient or PTC type typically.

Resistor color code

Resistor unit is ohms 

measurement thousands (K =kilo) and millions (M=meg)

100                =  .1k

1,000             =   1k

10,000           =  10k

100,000         =  100k

1,000,000      = 1M

 Resistor Symbols