8.ELECTRONICS:
Electronics involves the study of circuits and compenents that modify the intensity, direction or properties of electric currents.

8.1.ELECTRONIC COMPONENTS:
In this section,we will analyse the most common electronic components.

FIXED RESISTANCE OR RESISTOR: A fixed resistance or resistor opposes the flow of electric currents.Its value,which we measure in ohms,is indicated by a code of colours and numbers.








The first two stripes are replaced by two numbers,according to their color.The third stripe indicates the number of zeroes that we must add to the previous figure.The fourth stripe indicates the tolerance or the tolerance or the máximum deviation from the theoretical value.











VARIABLE RESISTANCE OR POTENTIOMETER: The value of a variable resistance or potentiometer can be adjusted between zero and the máximum value specified by the manufacturer.








RESISTANCE THAT DEPENDS ON A PHYSICAL FACTOR:

• Resistance that depends on temperature is called a thermistor.There are two types of thermisors:

1. Negative temperature coefficient:The resistance decreases as the temperature rises.
2. Positive temperature coefficient:The resistance increases as the temperature rises.

• LDR:Resistance that varies according to the amount of light received.The resistance decreases as the amount of light increases.These devices,like potentiometers,are often used in security systems,where they are parts of sensors.