Can I use cast iron on a hot plate? I'm Jewish and need to keep foods heated during the Sabbath and holidays. I am thinking of getting 2, 5 quart cast iron dutch ovens for this purpose. Is cast iron a good choice for to keeping foods heated on a hot plate? Or should I get glass or teflon pots? The periods could be 1 day but could also be up to 3 days if the holiday is right after or before a Sabbath. 

Im gonna put the pots on a long hot plate to keep warm for the length of time. I simply want to know if cast iron would be a good alternative to do this or do i need to get glass or teflon pots.
You can use any kind of pot on a hot plate. I can't see any reason cast iron would be a problem, unless the hot plate has a less durable surface and you're worried about scratching it.

The only thing that matters is whether the hot plate is powerful enough to keep your food above 140F for the entire time period. That depends much more on the size of the pots than the material they're made of.

If possible, I'd suggest checking with a thermometer to confirm. You can always do a dry run, and you don't have to wait 3 days. If it holds steady at a safe temperature for an hour or two, it should be fine.