hello guys please help me how to calculate the power dissipated by triac BT136,the load is ceiling fan with internal resistance of 320E
please find the below attachment
Simplistically, Vt = on-state voltage which is typically 1.4V (Max = 1.7V) times RMS current of .71875A = 1.006W to 1.22W
If you want to get more precise, you will have to specify your requirements more clearly.