Why DC motors have open slots?

Use of DC Motors in Mines: Operation, Inspection and Maintenance slot wedges in dc machine made of dc-machines-questions Which of the following dc generators will have negligible terminal voltage on no load? What are slot wedges in a dc machine made of? slot en español Slot wedges in a dc machine is made up of A cast iron B silicon steel C fibre D mild steel

slot milling Polarity of interpoles with respect to polarity of main poles in DC motors and generators Figure 4 SHUNT FIELD ARMATURE INTERPOLE FIELD SERIES FIELD