APPROXIMATELY FIVE MINUTES AFTER TAKEOFF, WHILE IN CRUISE FLIGHT, SMOKE APPEARED FROM THE RIGHT SIDE OF THE INSTRUMENT PANEL. THE PILOT INITIATED A FORCED LANDING IN AN OPEN FARM FIELD. PRIOR TO TOUCHDOWN FLAMES WERE PRESENT IN THE COCKPIT. AFTER THE LANDING, THE PILOT EXITED THE AIRPLANE, WITH MINOR INJURIES. THE AIRPLANE CONTINUED TO BURN. A SUBSEQUENT EXAMINATION FAILED TO REVEAL THE SOURCE WHERE THE FIRE ORIGINATED. THE PILOT DESCRIBED THE ORIGIN TO BE AN ELECTRICAL FIRE; HOWEVER, DURING THE EMERGENCY PROCEDURES HE MADE NO ATTEMPT TO DISENGAGE THE MASTER SWITCH.