A moving iron instrument gives correct reading when used at low frequencies high

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Question
A moving iron instrument gives correct reading when used at
Options
A. low frequencies
B. high frequencies
C. only one frequency
D. all frequencies upto a certain value

Correct Answer

only one frequency

Explanation

If frequency changes reactance of coil changes and reading is affected.

Measurements and Instrumentation problems

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1. A full wave rectifier type meter is used to measure the wave shape shown in figure. The voltmeter is calibrated to read rms value of sine wave. The reading of voltmeter will be
Options
A.
B.
C. 100 V
D. 111 V

2. 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

3. 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

4. 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

5. 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

7. Which of the following is true about an impulse voltage?
Options
A. It is a unidirectional voltage
B. Chopped impulse flashover does not occur
C. Time taken to rise is equal to time taken to fall
D. RMS value is always less than 50% of average value

9. In 3 phase power measurement by two wattmeter method, the reading of one wattmeter is zero. The power factor of load is
Options
A. 1
B. 0.5
C. 0
D. 0.8

10. Which power amplifier can deliver maximum load power?
Options
A. Class A
B. Class AB
C. Class B
D. Class C

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