4. (a) (i) Explain with neat diagram how rod gaps can be usedfor measurement of high voltages. Compare its performance with asphere gap.
(ii) Explain with neat diagram the principle of operation of anElectrostatic Voltmeter. Discuss its advantages and limitations forhigh voltage measurements.
Or
(b) A Rogowski coil is required to measure impulse current of 8kA having rate of change of current of 1010 A/sec. The voltmeter isconnected across the integrating circuit which reads 8 volts forfull scale deflection. The input to the integrating circuit is fromthe Rogowski Coil. Determine the mutual inductance of coil, R and Cof the integrating circuit.
