In an ideal voltmeter there is infinite resistance so because of which no current is flowing through it and the voltage reading is not affected.
The ohm's law stated that
V = I * R
In an ideal voltmeter I = 0 so V = 0 but the voltmeter does show some reading which defies the ohm's law. Please tell me how is this possible.
Best Answer
It is possible to have a perfect voltmeter: You can use a potentiometer with a current meter but you also need something with a standard voltage (standard cell, whose emf is larger than what you are trying to measure). It is a null method, that works by varying the sliding contact on the potentiometer until a zero current is registered. Zero current means no pd across an internal resistance so no "lost volts". Have a look here for more details.
Apparently "This null balance measuring method is still important in electrical metrology and standards work and is also used in other areas of electronics".