University of Mumbai 2008-3rd Sem B.E Electrical and Electronics Engineering Electrical Measurements & Measuring Instruments - Question Paper

(a)    State and define basic types of electrical measuring instruments.    rgv~

(b)    Derive the relation between the elecrostatlc and electromagnetic system of unit,

(c)    Explain why the Wheatstone bndge is not used for measuring low value of resistance.

(d)    State the advantages and disadvantages of flux meter.

2.    (a) Explain different types of error in detail.    10 (b) Use dimentional equation to find out whether the following expression is dimentionally iq

correct or not.

_R .^R* (^{u w2 R}|^c!)

⁴ w²r₁r₃c₃

whore R_|( R_J( R_a and R₄ are resistances.

C, is capacitance and W = 2 it/, / is frequency in Hz.

3.    (a) What are the different difficulties encountered in the measurement of high resistanco 7 io

Explain how these difficulties are overcome.

(b) Describe the operation of vibration galvanometer and derive the expression for 10 amplitude of vibration.

4.    (a) A moving coil instrument gives a full scale deflection of 10 mA when potential difference 10

across its terminal is 10 mV.

Calculate :

(i)    The shunt resistance required to be connected for a full scale deflection of 100 Amp.

(ii)    Series resistance for full scale reading of 1000 Volt.

(b) Explain Hay's bridge for measuring self inductance. Draw neat circuit and phasor 10 diagram. Derive expression for self inductance.

5.    (a) Explain any one type of power factor meter.    10 (b) A energy meter is designed to make 1200 revolution of disc for one unit of energy 1

(kWh). Calculate the number of revolution made by it when connected to load carrying 10 A, at 240 V and 0-4 power factor for 1 hour. If it actually make 1140 revolution.

Find the percentage error.

6.    (a) Draw the equivalent circuit and phasor diagram of a potential transformer. Derive 10

the expression for ratio and phase angle error.

(b) Explain the Laboratory type of d.c. potentiometer in detail.    10

7.    Write short notes on any three :    20

(a)    Synchroscope

(b)    Megger

(c)    Frequency Meter

(d)    Epstein Square Method

(e)    Paramagnetism and Ferromagnetism.