1. A dc wattmeter essentially consists of
A. two ammeters
B. a voltmeter and an ammeter
C. two voltmeters
D. a current and a potential transformer
2. High ac voltages are usually measured with
A. electrostatic voltmeters
B. voltmeter and current transformer
C. potential transformer and voltmeter
D. voltmeter and multiplier
3. A moving-coil instrument can be used to measure
A. low frequency a.c.
B. high frequency a.c.
C. direct current
D. d.c. and a.c. both
4. The resistance of a field coil may be correctly measured by using
A. a voltmeter and an ammeter
B. Schering bridge
C. a Kelvin double bridge
D. a Maxwell bridge
5. Which of the following instrument will be used to measure alternating current only?
A. moving-iron voltmeter
B. permanent-magnet type ammeter
C. induction-type ammeter
D. moving-iron (attraction-type) ammeter.
6. When connecting wattmeters to a load circuit consuming large current, it is necessary o use
A. potential transformers
B. isolation transformers
C. power shunts
D. current transformers
7. Which of the following electrical equipment cannot convert ac into dc?
D. mercury-arc rectifier
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