V- I Characteristics

When the peak  value of  applied  voltage is less than the break over   voltage  of triac  and no signal  is applied to the triac  it will block  both  positive  and negative half  cycles  of applied voltage. It can be turned on by  applying  positive and negative voltage  to the gate terminal with respect to the terminal MT1.

Some applications  of triac are light  dimmers speed  controls for electric  fans  and other  electric motors  and in the modern computerized  control  circuits of many household small and major  appliances.

Triac  can conduct in followings  cases: