In my physics textbook there is a question about a circuit:
In question b) We find out the current in the circuit is 0.003A. This is before the voltmeter is added.
In question c) a voltmeter is added that affects the p.d across the first 1k resistor which causes its voltage to drop from 3.0V to 2.0V. In the mark scheme they say R(from B to A) = 666.7 ohms which is means they did 2/0.003. How is it known the current doesn't change at all, or am I missing something?