# 555 Timer LED Flasher - What is Resistor ?

## Resistor

- Resistors are a specific, never-changing electrical resistance.
- Resistors are electronic components
- The resistor’s resistance
**restricts the flow of electrons**through a circuit. - Resistors are common elements of electrical networks and electronic circuits and are global in electronic equipment.
- Practical resistors as discrete components can be composed of various compounds and forms. Resistors are also implemented within integrated circuits.

Resistor

**Variable resistors**are called potentiometers- There is a fixed value of resistance between two terminals
- The moving part of the potentiometer is called the wiper.
**Four band resistor colour code**- 1st band provides the first digit of the code
- 2nd band provides the second digit of the code
- 3rd band is the multiplier
- 4th band indicates the tolerance value

Resistor

## Resistor colour code calculation

- The first band red has a value of 2
- The second band purple has a value of 7
- The third band has a multiplier of x 10
- The last band indicates a tolerance value of +/-5%
- Resistance value is 270Ω +/-5%

## Ohm's law

- The behaviour of an ideal resistor is dictated by the relationship specified by Ohm's law:

- 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).

## Series and parallel resistors

- The total resistance of resistors connected in series is the sum of their individual resistance values.

Serial Resistors

- The total resistance of resistors connected in parallel is the reciprocal of the sum of the reciprocals of the individual resistors.

parallel Resistor