Hart, 19, signed for City under Stewart Pierce last summer for £500,000, a deal which could rise to £1,500,000, from Shrewsbury after making 58 appearances for the Shrews.
He made his debut when he was 16 in the 2003/04 season and was touted as a huge prospect before moving to City, where he made his league debut against Sheffield United earlier this season.
He stands at 6.05 feet tall and has been capped at England U-19 level. Hart goes straight into the squad for todays game against Rotherham United.