Q:- While sending only Ether One wallet to another wallet(NO SMART CONTRACT), do we need to define the default gas limit and price?
i.e. 21000 * 3 OR 21000 * 4 OR 21000 * 5 etc
Or
I've need to use estimate gas function web3.eth.estimateGas(callObject [, callback])?
because the web3.eth.estimateGas function always return 21000 gas in all the case when I'm giving two params "value" and "to_address" to this function
eth_estimateGas estimates how much gas a transaction execution would require based on the current state of the blockchain. The gas consumed does not depend on the gas price (not directly, anyways, and in most transactions there is no relation at all).
The gas price is simply an indicator saying that "I am willing to spend up to gas price * max gas ether on this transaction". You must specify both a max gas and a gas price in your transaction (although many wallets will autofill both for you with some default/estimated values).
A pure ETH transfer from one externally owned account to another will always consume 21000 gas, so that is what estimate gas will always return. The final fee will then depend on your gas price.
