Re: Why does a cake take longer to bake in a smaller cake pan?

The baking time for the two pan sizes is largely determined by the depth of the 
cake batter.  When the batter is poured into the smaller pan, the depth of 
batter is greater than for the larger pan.

The depth of the cake batter is significant because the portion of the batter 
at the center of mass of the batter is the last to cook.  From the time the 
cake is placed into the oven, it takes longer for the batter in the smaller pan 
to come to the specified baking temperature than is the case for the larger pan.

Other than my own experiences with baking, the best references I can think of 
are heat transfer texts, particularly those sections dealing with conductive 
heat transfer.

I hope this answers your question.  If not, please don't hesitate to send 
another question.  Thanks.