oky today I made some expeiments on the motor, I opened it and I determined the the two wires connected to brushes to be the armature coil using digital multimeter, then also determined the two wires for the field coil, then I connected them on series and applied DC voltage and it rotated without any problems, but the strange thing is the other two wires rest I don't know for what they are , I measure the ohm resistance between them which is 0.8 ohm but between the armature about 5.6 ohm and between the field 2.9 ohm , and also the cross sectional area of the armature and field are the same but for the other two wires (0.8 ohm ) is lesser than the armature and filed wire.

I applied a small voltage on these two wires (0.8 ohm) but this make sparking.
I measured the DC voltage and ac voltage between them during rotation of motor but the reading always is zero.

so what may be the purpose of these two wires ?