ELECTRICAL MEASUREMENTS AND MEASURING INSTRUMENTS (PAPER 2) By SURESH KUMAR ....sureshkumarthegreat@yahoo.com

                                                CS-261
                            ELECTRICAL MEARUREMENTS
                           AND MEASURING INSTRUMENTS
                                (B.Tech 3rd Semester, 2122)
Time : 3 Hours                                                                                  Maximum Marks : 60
NOTE:- This paper consist of Three Sections. Section A is compulsory. Do any Four questions from
                 Section B and any two questions from Section C

                                   Section-A                                       Marks : 2 Each
1 Answer briefly the following:
   (a) Enemurate various sources of error encountered in measuring instruments.
   (b) Describe the international standard of mass and length.
   (c) Describe the various operating forces for proper operation of analogue instruments.
   (d) What are the requirements of a shunt?
   (e) Derive the dimention of e.m.f. in L,m,T,I system of dimensions.
   (f) Describe briefly different types of tests that are used for testing magnetic materials.
   (g) Explain different types of sweeps used in a CRO. Give their spheres of applications.
   (h) Enemurate the sources and null detectors used for a.c. bridges.
   (i) What is volt-ratio box? Explain its working and application.
   (j) Explain how instrument transformers are a better substitute for shunts and multipliers specially for high 4ranges.

                                            Section-B                                       Marks:5 Each

2. Desribe Rayleigh's current balance method of dteremination of absolute value of current. State the precautions to be
    taken to minimise errors.
3. An instrument spiring made of phosphor bronze strip has a length of 40 cm, a width 0.5 mm, thickness 0.08 mm.
    If modulus of elasitycity of phosphor bronze is 120 GN/M2, estimate the torquie exterted by the spring for a deflection
    of 60 degrees.
4 .Describe constructional qnd principle of working of permanent magnet moving ciol instrument. Write the relative torque
    equations for this instrument.
5. Explin with the help of phaser diagram how three-phase power of star connected load can be measured with the help of
    two wattmeters.
6. Describe the constructional and working of a coordinate type a.c. potentiometer. How an unknown voltage can be
    measured with it.Discuss the sources of error in this type of instrument.

                                             Section-C                                      Marks : 10 Each

7. The four arms of a hay's a.c. bridge are as follows:
    AB is the coil of unknown impedence;
    BC is non reactive resistor of 1000 ohms;
    CD is non-reactive resistor of 833 ohms in sesies with a standard capacitor of 0.38 uF; and
    DA is non-reactive resistor of 16800 ohms.
    Supply frequency is 50 Hz.
    Determine the value of unknown impedence. Derive the condition for balance and the phasor diagram under balanced
    condition.
8.(a) Describe a method to detemine experimentlly the flux density in a specimen magnetic material using a ballastic
        galvanometer. What correction fot the flux in air space between the specimen and the coil is applied.
   (b) A transformer operating at 400 V, 50 Hz gives a total loss of 100 W, of which 70 W is due to hysteresis. If the
        transformer is to be operate at 100 V, 100 Hz. What would be tha loss due to hysterisis and eddy currents?
9 Write notes on the following:
    (a) Measurement of voltage, frequency and phase angle by C.R.O.
    (b) Testing of CTs and PTs.
    (c) Measurement of high resistance.

ELECTRICAL MEARUREMENS AND MEASURING INSTRUMENTS

PAPER NO.1

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PUT ON JUNE, 2K2