helo,
now i got 1 project about design the  electromagnetic contactor.
The core of the contactor is silicon steel.
the shape of the cores are U shape n l shape.In the U shape core,the horizontal part is bigger than vertical part.The area of the horizontal part is (0.015m*0.015m) n the area of the vertical parts is (0.014m*0.014m).The ai gap between the cores is 0.0013m.
The  coils is round on the horizontal part.
1)How i can find the number of the turn(N) for the coil?
2)the current(I) required?
  The information given:
 The force required is 58.9N to connect the two cores.
 When voltage is 154V(70% of 220V),the cores must b connect.
 when voltage drop to 66V(30% of 220V),the cores non-connect.
3)what is the force,when the voltage is 66V?

Actually,i had tried to find it b4.but the turn is to big.
When i fix the I =0.5A, the turn is 18000
(the current may b can assume ourself,it arround 0.3A to 0.9A).
Is it we need to find the resistance(R) 1st to find the N ?or we assume the R ourself too?