Rhodes, who made his Scotland Under-21 debut against Belgium on Thursday, headed in the opener from Benik Afobe's cross.
The youngster's throughball after 58 minutes set up Gary Roberts for a cute dink over advancing County keeper Stuart Nelson to make it 2-0.
Rhodes then finished into the roof of the net from close range from Afobe's lay-off five minutes later for his 20th goal of the season.
Huddersfield, four points clear of third-placed Peterborough, have now gone 18 league games unbeaten, breaking the record for an unbeaten run in a single season set in 1925.
Rhodes could have had a hat-trick but he miscued an attempted close-range shot in front of an empty goal while County, who have now lost six of their last seven games, rarely threatened.