a battery of 6 volts is short circuited by a copper wire. What will be the potential difference across its terminals?
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According to me it should be 0, as the battery has short circuited so their should be no charge flow so it should be zero. But the answer is 4, HOW?

 

You're correct the answer is 0, but you're not correct in the reason why.

An answer of 4 is wrong.

 

Was the internal resistance of the battery mentioned in the problem statement. Perhaps the 4 refers to 4A, which might be the short-circuit current.

 

If can be 4V only if the resistance of the wire is twice that of the battery internal impedance.

 

a battery of 6 volts is short circuited by a copper wire. What will be the potential difference across its terminals?
....
According to me it should be 0, as the battery has short circuited so their should be no charge flow so it should be zero. But the answer is 4, HOW?

So if you short out your car battery, do you REALLY expect there to be no charge flow?

Always, always, ALWAYS ask if the answer makes sense!

The answer most certainly is NOT equal to 4, if for no other reason than 4 is a number and not a voltage.

Always, always, ALWAYS track your units!

 

In theory, a 6V battery cannot be 6V and 0V at the same time.

In practice, you have to include real values.

A short is never 0Ω
The internal resistance of a real battery is never 0Ω.
A real battery cannot supply infinite current.