Electrical Engineering ⇒ Topic : Basic principle of the ammeter and the voltmeter is the same
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David
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The basic principle of the ammeter and of the voltmeter is the same. Both are current operated devices i.e. deflecting torque is produced when current flows through their operating coils. In the ammeter, the deflecting torque is produced by the current we wish to measure, or a certain fraction of that current. In the voltmeter, the deflecting torque is produced by a current which is proportional to the potential difference we wish to measure. Thus, the same instrument can be used as an ammeter or voltmeter with proper design. The following types of instruments are used for making voltmeters and ammeters (i) Permanent-magnet moving coil type (ii) Dynamometer type (iii) Moving-iron type (iv) Hot-wire type (v) Electrostatic type (for voltmeter only) (vi) Induction type The instrument at Sr. No. (i) can be used for d.c. work only whereas instrument at Sr. No. (vi) is employed for a.c. work only. However, instruments from Sr. No. (i i) to (v) can be used for both d.c. and a.c. measurements | |
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