Measurements and Instrumentation problems
- 1. A dynamometer wattmeter is connected in ac circuit. The measured power is
Options- A. rms power
- B. average power
- C. peak power
- D. instantaneous power Discuss
Correct Answer: average power
Explanation:
All wattmeters measure average power over a cycle.
- 2. A meter with a resistance of 100 ? and a full scale deflection of current of 1 mA is to be converted into voltmeter of 0 - 5 V range. The multiplier resistance should be
Options- A. 490 ?
- B. 5000 ?
- C. 4900 ?
- D. 5100 ? Discuss
Correct Answer: 4900 ?
Explanation:
.
- 3. A dynamometer wattmeter is connected in ac circuit. The reading will be
Options- A. V-A product
- B. average power
- C. peak power
- D. instantaneous power Discuss
Correct Answer: average power
Explanation:
Wattmeter measures average power over a cycle.
- 4. In figure the bridge is balanced when Z4 is
Options- A. 120?70°
- B. 187.5? - 10°
- C. 187.5? - 70°
- D. 333.3? - 70° Discuss
Correct Answer: 187.5? - 70°
Explanation:
.
- 5. 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 Discuss
Correct Answer: Voltmeter having sensitivity of 10 kW/V
Explanation:
Resistance of voltmeter should be very high as compared to 20 k?.
- 6. 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 Discuss
Correct Answer: it does not load the circuit at all
Explanation:
Since the circuit is not loaded, the accurate value of dc voltage is measured.
- 7. 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 Discuss
Correct Answer: high resistance milli-voltmeter
Explanation:
The output voltage is very small. So we need a milli voltmeter.
- 8. 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 Discuss
Correct Answer: D/A converter
Explanation:
D/A converter changes digital output to analog output.
- 9. 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 Discuss
Correct Answer: A is true R is false
Explanation:
Wattmeter measures active power.
- 10. 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 Discuss
Correct Answer: CT
Explanation:
CT is operated with secondary short-circuited otherwise a high emf would be induced across secondary.
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