JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONIC MEASUREMENTS Previous Question Paper (September/October - 2023 - R16)
i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Why the scale of Moving Iron instrument is calibrated non- linearly?
Answer
The scale of a Moving Iron (MI) instrument is non-linear because the deflecting torque is proportional to the square of the current flowing through the coil. The relationship is expressed as
Describe errors in measuring instruments.
Answer
Errors in measuring instruments represent the difference between the measured value and the true value of a quantity. These are broadly classified into three categories:
- Gross Errors: Primarily caused by human mistakes in reading, recording, or using instruments incorrectly. These can be minimized by taking multiple readings and using proper care.
- Systematic Errors: These are consistent, repeatable errors due to instrument defects (e.g., weak springs, friction), environmental effects (e.g., temperature, pressure), or observational errors (e.g., parallax). They can be corrected by calibration or applying environmental corrections.
- Random Errors: These are unpredictable, small variations that occur even after systematic errors are removed. They are caused by unknown fluctuations in experimental conditions and are typically handled using statistical analysis, such as calculating the mean of multiple observations.
Mention the significance of standardization in potentiometers.
Answer
Sign in to view the complete answer paper.
Compare a potential transformer and a regular power transformer?
Answer
Sign in to view the complete answer paper.
What are various errors observed in energy meters?
Answer
Sign in to view the complete answer paper.
Write about the shape of scale in electrodynamometer wattmeter.
Answer
Sign in to view the complete answer paper.
State the conditions for AC bridge balancing.
Answer
Sign in to view the complete answer paper.
List the advantages of using standard capacitor in maxwell’s bridge.
Answer
Sign in to view the complete answer paper.
What is the function of photo diodes?
Answer
Sign in to view the complete answer paper.
Explain about Bourdon tube usage in pressure measurement.
Answer
Sign in to view the complete answer paper.
Part B
State the basic requirement of any measuring instruments. How the various measuring instruments are classified?
Answer
Sign in to view the complete answer paper.
Explain various errors and their compensation used in ammeters and voltmeters.
Answer
Sign in to view the complete answer paper.
Explain the operation of electrometer type electrostatic voltmeters.
Answer
Sign in to view the complete answer paper.
A moving coil instrument gives a full scale deflection of 15mA when the potential difference across its terminals is 150mV. Calculate i) The shunt resistance for a full scale deflection corresponding to 100A and 130A. ii) The series resistance for full scale reading with 600V. Calculate the power dissipated in each case.
Answer
Sign in to view the complete answer paper.
With the help of a neat circuit diagram explain Crompton’s potentiometer and it’s working. How a true zero is obtained in a Crompton’s pot?
Answer
Sign in to view the complete answer paper.
In the measurement of power by a polar potentiometer, the following readings were obtained: Voltage across a 0.2 Ω standard resistance in series with the load=1.46∟320, Voltage across a 200:1 potential divider across the line = 1.37∟560 V. Estimate the current, voltage, power and power factor of the load.
Answer
Sign in to view the complete answer paper.
Explain the construction and working of a current transformer with neat sketch and state the expressions for its ratio and phase angle errors.
Answer
Sign in to view the complete answer paper.
Explain with neat sketches the measurement of active and reactive powers in balanced and unbalanced systems
Answer
Sign in to view the complete answer paper.
Explain the working of LPF wattmeter with a neat sketch.
Answer
Sign in to view the complete answer paper.
Explain with a neat sketch the construction and working principle of a single phase energy meter and derive an expression to show that number of revolutions/sec is proportional to the power.
Answer
Sign in to view the complete answer paper.
An energy meter is designed to make 100 revolutions of the disc for one unit of energy. Calculate the no. of revolutions made by it when connected to a load carrying 25A at 230V at 0.85 pf for an hour. If it actually makes 360 revolutions, find the percentage error.
Answer
Sign in to view the complete answer paper.
Explain the principle of working of a Kelvin’s double bridge for measurement of unknown low resistances. Explain how the effects of contact resistance and resistance of leads are eliminated.
Answer
Sign in to view the complete answer paper.
Draw the circuit diagram of H.V. Schering bridge. Derive the condition for this bridge to be balanced.
Answer
Sign in to view the complete answer paper.
Define quality factor of a coil. Why is Hay’s bridge suitable for the measurement of inductance of high Q coils.
Answer
Sign in to view the complete answer paper.
Describe the principle of operation of LVDT.
Answer
Sign in to view the complete answer paper.
A transducer that measures force has a normal resistance of 250 Ω, forms a four arm strain gauge bridge and is excited by 6.5V DC. When the force of 0.12N is applied, all the four strain gauge resistances are changed by 5.5Ω. Find the output voltage and determine its sensitivity.
Answer
Sign in to view the complete answer paper.
Explain the working, construction and applications of thermistors. Compare resistance temperature characteristics of a typical thermistor and platinum.
Answer
Sign in to view the complete answer paper.
Explain the principle of piezo electric transducer? And mention its advantages and applications.
Answer
Sign in to view the complete answer paper.