few questions

[not_me]

1: what exactly does a capacitor do and how is it used (brief explanation)

2: what is a mosfet/triac/diac?

thank you in advance

 

[tavib]

1. A capacitor accumulate electric charge and energy, the charge is accumulate on plates and energy in form of electric filed between them.
When an amount of + charge is injected into one plate, the fied created by this charge will repel the + charge from second plate and attract the - charge, so if a current enter into plate then the same current will go out from second plate, and seem like current pass through capacitor, but only seem because the charger remain on plates and the electric field between plates become higher and higher, with other words the voltage over capacitor increase when current "pass' through it. If current change it direction then, if capacitor is charged from previous current, the capacitor voltage start to decrease down to 0 and if current persist then the capacitor start to charge in reverse voltage. With other words the current "pass" through capacitor while voltage over it have any variation.

2. MOSFET come from Metal Oxide Semiconductor Field Effect Transistor and is a type of transistor very used into digital ICs and as power transistor for switching mode circuits.

A triac is a static switch for AC current, that have two AC main terminals and a gate terminal for trigger. Normaly the current not pass between AC terminals, but a positive voltage/current is applied to gate relative to 1st AC terminal, the trial become conductive and will conduct AC current in both directions. This conduction is maintained after the trigger pulse(which can be a short pulse) while the current is hold over a value called susteined value or holding value of current. If current decrease under this value the triac will go back into unconductive state.

Diac is similar with triac but don't have the trigger terminal, this device is triggered when the AC voltage over it increse over a specified value, when the diac go into conductive state and voltage over it normal decrease down to 1-2 V.