I'm trying to understand national debt. I gather that the United States, and other nations with central banks, accrue debt basically by printing new money at their central bank. This, I hypothesize, is to avoid giving private banks too much power. What I'm having trouble with is understanding the interest rate on these "loans". Given the peculiar circumstance of the arrangement, the national debt provides a way to monitor the possible inflationary effects of printing new money. It is paid back only as a way to take money out of circulation, and/or to allow the government to solidify wealth created by the economic stimulus, and to invest it abroad. But there's no apparent reason for one part of the government to charge another part of the government interest, so far as I can tell -- unless it represents something else. So what is the interest rate doing? And is there something I'm missing in my explanation?