Correct Answer - Option 3 : Voltmeters
The electrostatic type instrument use static electrical field to produce the deflecting torque. These types of instrument are generally used for the measurement of high voltages.
The principle of working of all electrical measuring instruments depends upon various effects of electric current or voltage as shown in the table given below.
Effect of Electricity
|
Type of Instrument
|
Suitable for
|
Magnetic Effect
|
Ammeters, voltmeters, watt meters and energy meters
|
D.C. and A.C Current
|
Electro dynamic effect
|
Ammeters, voltmeters, watt meters
|
D.C and A.C Current
|
Electromagnetic induction effect
|
Ammeters, voltmeters watt meters and energy meters
|
A.C Current only
|
Thermal effect
|
Ammeters, voltmeters
|
D.C and AC current
|
Chemical Effect
|
Ampere-hour meters
|
D.C only
|
Electrostatic effect
|
Voltmeters
|
D.C and A.C current
|