21. Which of the following instruments indicates the instantaneous value of the electrical quantity being measured at the time at which it is being measured?
Absolute Instruments
Indicating Instruments
Recording Instruments
Integrating Instruments
Answer.2. Indicating Instruments
Explanation:
Indicating Instruments: These indicate the quantity being measured by means of a pointer that moves on a scale. These instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured.
Example: Ammeter, Voltmeter, Wattmeter
22. Errors that occur after taking care of all gross and systematic errors are called as:
Environmental errors
Limiting errors
Instrumental errors
Random errors
Answer.4. Random errors
Explanation:
After calculating all the systematic errors, it is observed that there are still some more errors in the measurement. These random errors are those errors that occur irregularly and are random with respect to their sign and size.
Random and unpredictable fluctuations in temperature, voltage supply, and mechanical vibrations of the experimental set-up may lead to random errors. The important property of a random error is that it adds variability to the data but does not affect average performance for the group. For this reason, random error is sometimes referred to as noise.
23. A resistance measurement reading is 68.0 Ω. The number of significant figures in the reading is:
2
1
3
4
Answer.3. 3
Explanation:
Significant figures are the number of digits in a value, which help to contribute to the degree of accuracy of the value.
We start counting significant figures at the first non-zero digit till the end of non-zero digits or zero digits.
Count the number of significant figures for an assortment of numbers.
It is necessary to indicate the quantity of something in an absolute manner.
Start counting significant figures at the first non-zero digit till the end of the non-zero digits or zero digits.
The first non-zero digits are 6 and the last zero digits are 0.
Start counting from 68.0,
The Significant Figures are 6 8 0
We get there are a total of 3 digits numbers that are finally considered as significant figures.
24. The errors mainly caused by human mistakes are
Gross error
Instrumental error
Observational error
Systematic error
Answer.1. Gross error
Explanation:
Gross errors include all the human mistakes while reading and recording. Mistakes carried out in calculating the errors also fall within this category. For example, while taking the reading from the meter of the instrument, a person may read 21 as 27 or 31.
25. Which of the following errors occurs in only in ac measurements?
Errors due to change in impedance of the coil and stray fields
Errors due to hysteresis and stray fields
Errors due to change in impedance of the coil and change in the magnitude of the eddy currents
Error due to hysteresis
Answer.3. Errors due to change in impedance of the coil and change in the magnitude of the eddy currents
Explanation:
Errors due to the change in impedance of the coil and change in the magnitude of the eddy current have only occurred in ac measurements.
Hysteresis errors and errors due to stray magnetic field fields have occurred in both AC & DC measurements.
In ac measurements, the change in frequency causes an error due to the change in the magnitude of eddy currents set up in the metal portion of the instruments.
The reactance of the operating coil changes by the change in frequency.
At high frequencies, the meter will give a reading lower than the actual value and at low frequencies, the meter give a reading higher than the actual.
This type of error can be eliminated only if the impedance of the coil is independent of the frequency. This is achieved by having a capacitance in shunt with the swamping resistance.
26. In case of overdamping, the instrument will become
Oscillating
Dead
Fast and sensitive
Slow and lethargic
Answer.4. Slow and lethargic
Explanation:
In case of over damping, the instrument will become slow and lethargic and it rises very slowly from its zero position to final position
An over-damped system would never allow the system to reach the desired end state since it is over-damped and that is why they are never used.
27. Which of the following types of errors are dynamic errors?
Human errors
Observational errors
Instrument errors caused due to slow response of instruments
Environmental errors
Answer.3. Instrument errors caused due to slow response of instruments
Explanation:
Dynamic errors are caused by the inertial properties of measuring instruments or equipment.
The various dynamic characteristics are:
i) Speed of response
ii) Measuring lag
iii) Fidelity
iv) Dynamic error
28. Error due to improper zero adjustment is classified as
Environment error
Instrument error
Random error
Operator error
Answer.2. Instrument error
Explanation:
Instrumental Errors: This error may arise due to imperfection or faulty adjustment of the instrument with which measurement is being taken.
Error due to improper zero adjustment
Due to the inherent shortcomings of the instruments
Due to the misuse of the instruments
Due to the loading effect
29. The percentage limiting error, in the case of an instrument reading of 10 A with a 0 to 200 A ammeter having a guaranteed accuracy of 1% full-scale reading is
50%
20%
10%
25%
Answer.2. 20%
Explanation:
Full scale reading = 200 A
Guaranteed accuracy = 1% of full-scale reading = 0.01 × 200 = 2 A
Measured value = 10 A
Limiting Error = Gurranted Accuracy/True Value = 2/10
Limiting Error% = 20%
30. The various Source of error in Measuring Instrument is
Insufficient Knowledge
Poor Design
Poor Maintenance
All of the above
Answer.4. All of the above
Explanation:
The various Source of error in the Measuring instruments are as under
Insufficient knowledge of process parameters and design conditions
Errors caused by the person operating the instrument
Change in process parameters, irregularities, etc.
Poor maintenance
Poor design
Certain design limitations
31. Which of the following are integrating instruments?
Ammeters
Voltmeters
Wattmeters
Ampere-hour and Watt-hour meters
Answer.4. Ampere-hour and Watt-hour meters
Explanation:
An integrating instrument is an analog device that is used to measure the total energy supplied by the circuit in a given amount of time and is independent of the total energy consumed. Example: The best example of integrating systems is the watt-hour meter and Ampere Hour Meter.
