Measurement of High Resistance using the Loss of Charge Method.

High resistance refers to?
An electrostatic voltmeter of infinite resistance is connected between the cable conductor such that joint capacitance is 500µF. If the voltage falls from 400V to 100V in one minute then the insulation resistance of the cable will be?
Which of the following method is used for the measurement of Medium Resistance?
A capacitor is connected to a battery, The force of attraction between the plates when the separation between them is halved?
When Using multimeter, applied voltage is to be disconnected from the circuit because?