MCQs on Electrical And Electronics Measurements

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01․ The terminals across the source are ______________________________ if a current source is to be neglected.
short circuited
open circuited
replaced by a source resistance
replaced by a capacitor

To neglect a current source, is to make the current zero in that branch. In order to achieve this, the branch should be open circuited then only no current will flow through that branch.

02․ In two wattmeter method of power measurement if the total power is measured by one wattmeter only then power factor of the system is
none of above.

If the total power is measured by one wattmeter method instead of two wattmeter method, that means one wattmeter readings is zero.

03․ Deflection method direct measurements are most widely used as these are
most simple and least time consuming.
least time consuming.
most simple.
most accurate.

In deflection method direct measurements, the value of the unknown quality is determined with the help of measuring instruments having a calibrated scale indicating the quantity under the measurement directly, such as measurement of current by an ammeter. This process is also less time consuming.

04․ A null type instrument as compared to a deflected type instrument has
a lower sensitivity.
a faster response.
a higher accuracy.
all of the above.

In null type instrument, a zero or null indication leads to determination of the magnitude of measured quantity. In deflection type instrument the measured quantity produces some physical effect which deflects or produces a mechanical displacement in the moving system of the instrument. These types of instruments are suited for measurement under dynamic conditions. But the null condition depends upon some other known conditions. So the null type instruments are more accurate and highly sensitive as compared to deflection type instruments.

05․ The use of __________________ instruments is merely confined within laboratories as standardizing instrument.

Absolute instruments are those instruments which indicate the quantity to be measured in terms of the constants of the instrument and in order to find out the quantity in practical units, no previous calibration or comparison is necessary in this case. So these instruments are rarely used and their use is being merely confined within laboratories as standardizing instruments.

06․ Comparison methods are used
when a high accuracy of measurement is required.
because they are most simple.
because they take least time in measurement.
because they are expensive.

In comparison methods, the value of unknown quantity is determined by direct comparison with a standard of a given quantity. So these methods have a high accuracy of measurement.

07․ Systematic errors are
environmental errors.
observational errors.
instrument errors.
all of the above.

Systematic errors are the error that remains constant or change according to a definite law on repeated measurement of the given quantity. These errors can be evaluated and their influence on the results of measurement can be eliminated by the introduction of proper correction. There are three types of systematic errors - instrumental error, environmental and observational error.

08․ The smallest change in measured variable to which instrument will respond is

The resolution of any instrument is the smallest change in the input signal (quantity under measured) which can be detected by the instrument. It may be expressed as an actual value or as a fraction or percentage of the full scale value.

09․ Which of the following are integrating instruments?
Ampere hour and watt hour meters.

Integrating instrument are those instruments which measure total quantity of electricity delivered in a particular time.

10․ The errors mainly caused by human mistakes are
gross error.
instrumental error.
observational error.
systematic error.

The errors occur because of mistakes in observed readings, or using instrument and in recording and calculating measurement results. Gross errors are due to human mistake in reading or in using instrument or error in recording observations.