Correct option is C
(a) Thermocouple
Thermocouples can measure both AC and DC temperatures.
They are primarily used for temperature measurement by converting thermal potential differences into electrical potential, but are not typically used for direct electrical measurement of current or voltage.
(b) Rectifier
Rectifier meters, which include rectifier-type instruments, can measure AC by converting it to DC.
Thus, they are used for measuring both AC and DC after rectification.
(c) Electrostatic
Electrostatic meters measure voltage through the force exerted in an electrostatic field.
They are uniquely suited to measuring high voltage AC and can also measure DC, but their design and operating principle make them predominantly useful for AC applications, particularly at higher voltages.
Among the options, this is the one most specific and suitable primarily for AC measurements.
(d) Moving coil
Moving coil meters, also known as D'Arsonval meters or galvanometers, are generally used to measure DC.
These meters rely on a magnetic field generated by a fixed coil and a moving coil, where the moving coil deflects in response to DC.
While each of these meters has specific applications where they excel, the electrostatic meter is the type that is typically used in scenarios where only AC measurements are relevant, particularly at higher voltages. Thus, option (c) Electrostatic is the correct answer to this question.
