A circuit shown below is a 555 monostable circuit. Normally a 9 volt battery would be connected but this circuit is powered by a transformer. The circuit has be drawn on 'Crocodile Technology 3D' software and then animated (using graphics/animation software). A circuit can be drawn with this software and tested on screen. Furthermore, it can be seen in three dimensions and rotated into almost any position.

The bulb only illuminates when the push switch is pressed. It works once and then stops. The switch must be pressed again for the bulb to light.

Increasing the value of the resistors and capacitor extends the time the bulb is illuminated.

Below are some of the main components used in a 555 monostable circuit. Name all the components and explain the role they play.

7. In your opinion, which of the components shown above is the most important in the 555 monostable circuit? Explain your answer.