Every time you send BTC you DO send the entire amount of each input to an address up to the amount being sent plus fee and includes inputs of other addresses as necessary. Every time you receive btc to an address it is a separate input and are entities upon themselves. What you don't spend is returned as "change" usually to a new address, which is commonly referred to as a change address. The bitcoin protocol does not allow any portion of a input to be spent. Each time the entire input is sent. So if you have 1 bitcoin in one address as one input and you send someone .05 btc with a .0001 tx fee, 0.9499 btc will be returned to you as change, usually to a new address unless you clicked the option in electrum to not use change addresses, then the change will be returned as a new input to the same address it was sent from. Every time you receive money, electrum will show a new address to receive the next payment and each time you send btc a new change address will be used.