A piece of paper wrapped tightly on a wooden rod is found to get burnt when held over a flame, but similar piece of paper when wrapped around a brass rod does not burn, why?

Wood is a bad conductor and brass is a good conductor of heat.
When a paper is wrapped around wood and is held over a flame, a sufficient quantity of heat supplied to it resides in the paper. Therefore the paper gets burnt.
On the other hand, if the paper is wrapped around the brass rod, the heat supplied to paper gets conducted into the interior of metal rod and hence the paper wound over metal rod does not get burnt.