As far as I understand if I send some 0.02 BC from an address in my Electrum Wallet containing 0.05 BC then Electrum
- sends 0.02 to the given target address of the recipient
That's correct. The client will send the selected amount to any valid address you enter/paste into the send tab.
- creates automatically a new empty address
Electrum won't create a new one. Like o_e_l_e_o said, it will select one from your list of already existing change addresses.
- send the remaining change of 0.03 BC to this new address
You are forgetting one important element of every bitcoin transaction. The mining fees. Each transaction requires you (the sender) to pay a transaction fee to the miner to include your transaction into a new block. So your change address will be funded with 0.03 BTC minus whatever fee you ended up paying.