Assertion (A): When a wattmeter is used for low impedance loads, the pressure co

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Question
Assertion (A): When a wattmeter is used for low impedance loads, the pressure coil is connected across the load.
Reason (R): A wattmeter measures apparent power.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

Correct Answer

A is true R is false

Explanation

Wattmeter measures active power.

Measurements and Instrumentation problems

Search Results

1. A digital frequency counter can be converted to DVM by addition of a suitable
Options
A. voltage controlled oscillator
B. D/A converter
C. power amplifier
D. operational amplifier

2. In a thermocouple temperature transducer, the output voltage is usually measured by
Options
A. high resistance ammeter
B. high resistance voltmeter
C. high resistance milli-voltmeter
D. none of the above

3. Potentiometer method of dc voltage measurement is more accurate than direct measurement using a voltmeter because
Options
A. it loads the circuit to maximum extent
B. it loads the circuit moderately
C. it does not load the circuit at all
D. it uses centre zero galvanometer instead of Voltmeters

4. Which of the following voltmeters would you use for measuring voltage across 20 k? resistance?
Options
A. Voltmeter having a resistance of 5 k?
B. Voltmeter having a sensitivity of 1 kW/V
C. Voltmeter having sensitivity of 10 kW/V
D. None of the above

6. In which of the transformer is the secondary nearly short circuited under normal operating conditions?
Options
A. CT
B. PT
C. Distribution transformer
D. Power transformer

7. A single phase energy meter has the rating 1200 resolutions/ kWh. If a 500 W electric gadget is used for 4 hours, the energy meter will make
Options
A. 1200 revolutions
B. 1800 revolutions
C. 2100 revolutions
D. 2400 revolutions

8. If reference sound pressure P₀ is 2 x 10^-5 N/m², a sound pressure of 90 dB is equal to
Options
A. 0.632 N/m²
B. 0.707 N/m²
C. 0.835 N/m²
D. 0.925 N/m²

9. Assertion (A): A hot wire ammeter has a cramped scale.
Reason (R): The heat is proportional to square of current.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

10. Consider the following statements: In a differential amplifier using JFET, the differential output offset is due to
1. mismatch between FET parameters
2. difference in values of resistances used in circuit
3. variation in supply voltage.
Of the statements, the correct statements are
Options
A. 1 and 2
B. 1, 2, 3
C. 2, 3
D. 1, 3

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