Hi Rahul, let me explain this to you with the help of an example:
Ram is our tenant who pays us Rs.1000 through cheque as rent.
What should be the journal entry for above?
1. Bank A/c Dr. 1000
To Rent A/c 1000
2. Bank A/c Dr. 1000
To Ram A/c 1000
Journal entry 1. is correct because it records receipt of money in bank (Debit what comes in). Rent A/c is being credited because all Incomes/Revenues are credited..
Journal entry 2 is wrong because it wrongfully credits Ram. As Ram is neither our debtor or creditor, so he cannot be a giver. I will give you another example for this. If we sell goods to Ram and he pays cash for it, then we credit Sales A/c and not Ram A/c because we are receiving cash against sales and not from Ram (since Ram is neither our debtor or creditor).
I hope I have made my point clear and from above it follows that when bank pays us interest, our balance with bank increases, so bank is a receiver in a way, so it is debited. Your confusion arises from the fact that on the one hand bank balance is increasing and on the other bank is paying interest. Since we are receiving money on account of interest, that is why interest account is credited and not the bank (since bank does not owe us interest because the moment interest becomes due, it pays us, just like cash payment).