bee 2123 final bi asma (modul)

BEE 2123

SOALAN DALAM BAHASA INGGERIS

Q1 (a) A current meter that has an internal resistance of 50 W is used to measure the current

through resistor RB branch shown in the circuit of Figure Q1(a).

(i) Draw the new circuit that showing the position of the ammeter. (2)

(ii) Determine the percentage of error of the reading and find the percentage of error

of the reading if the voltage supply is change to 10 V. (4)

(iii) Give your comment on this situation. (1)

(7 marks)

(b) A voltmeter is used to measure the voltage across resistor RA in the circuit of Figure

Q1(b). The sensitivity of the meter is 200 kW/V.

(i) Draw the new circuit that showing the position of the voltmeter. (2)

(ii) Find the voltage reading across RA and the percentage of error of the reading if

the range of voltmeter is 3 V. (4)

(iii) Give your comment on this situation. (1)

(7 marks)

(c) A 1 mA full-scale deflection current meter movement is to be used in an ohmmeter

circuit of Figure Q1(c). The meter movement has an internal resistance Rm of 100 W

and 5.0 V battery will be used in the circuit. Calculate,

(i) The value of standard resistance, RSTD. (1)

(ii) The value of RX that would cause 25%, 50%, 75% deflections and show the

position of pointer in the meter for every case. (3)

The ohmmeter is redesigned to make more efficient whereby one resistor R2 is

connected parallel with the PMMC and current meter is fixed to 0.5 mA of FSD.

(iii) Draw the new circuit of the ohmmeter. (1)

(iv) Calculate R2 when there is 15% drop in Eb and calculate Rx if the meter indicates

75% of FSD. (4)

(v) Explain the function of R2. (2)

(11 marks)

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BEE 2123

Q2 (a) State two of most common methods to measure power in AC circuit and draw the

circuit of each method.

(3 marks)

(b) In one design of the AC ammeter, several factors need to be considered. The meter has

the following specifications:

PMMC instrument with FSD = 200 µA and Rm = 900 W;

Current transformer with Ns = 6000 and Np = 5;

Diodes with VF ≈ 0.3 Vpeak;

Meter series resistance, Rs = 270 kW;

Transformer shunt secondary resistance, RL = 98.7 kW.

(i) Draw the rectifier ammeter circuit.

(ii) Calculate the level of transformer primary current for instrument FSD.

(7 marks)

(c) A pendarflour lamp circuit shown in Figure Q2(c) consists of a choke with resistance,

R = 100 W and inductance, L = 5 H with supply voltage, Vs = 586.9 cos 314t V. If the

wattmeter is installed across the pendarflour lamp, determine,

(i) Power factor (pf)

(ii) Real power (P) and Reactive power (Q)

(iii) Apparent power (S) and Complex power(S)

In order to make the power factor to unity, one capacitor needs to be added in the

circuit in series. For the new circuit, find

(i) Power factor (pf)

(ii) Real power (P) and Reactive power (Q)

(iii) Apparent power (S) and Complex power(S)

(iv) The value of added capacitor and draw the new circuit with label.

(Hint: use rms value for all calculation)

(15 marks)

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BEE 2123

Q3 (a) A Wheatstone bridge consists of four resistors, R1, R2, R3 and R4 respectively at every

single arm at every single arm. Show that the Wheatstone bridge in balance condition by

deriving the related equations and the diagram. Show all the related steps.

(5 marks)

(b) A Wheatstone bridge is connected for a Varley loop test as shown in Figure Q3(b).

When the switch S is in position a, the bridge is balanced with R1 = 1000 W, R2 = 100

W and R3 = 53 W. When S in position b, the bridge is balanced with R1 = 1000 W, R2 =

100 W and R3 = 52.9 W. If the resistance of the shorted wire is 0.005 W/m, find the

distance in meter the bridge has a short to ground occurred.

(10 marks)

(c) The radio-frequency bridge shown in Figure Q3(c) is balanced and Zx is shorted with

the following result conditions:

Z1 = (120 – j159) W

Z2 = – j1592 W

Z3 = 10 W

Z4 = (100 – j132.6) W

The unknown impedance is connected across the Zx terminals and the bridge is

rebalanced with the following conditions:

Z1 = (120 – j144.7) W

Z2 = – j1592 W

Z3 = 10 W

Z4 = (100 – j144.7) W

Find the equivalent-series elements for the unknown impedance, Zx.

(10 marks)

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BEE 2123

Q4 (a) Figure Q4(a) shows a basic block diagram of an oscilloscope. Give the name and

function of each subsystem as numbered 1 to 12 in Figure Q4(a).

(12 marks)

(b) Determine the amplitudes, frequencies and phase difference of the two waveforms as

illustrated in Figure Q4(b).

(5 marks)

(c) For an analog oscilloscope, XY mode in horizontal control section is fixed into vertical

input frequency, Fy = 150 Hz and the horizontal input frequency, Fx = 100 Hz. From the

information given,

(i) Draw the waveform of vertical input frequency, Fy and horizontal input

frequency, Fx.

(ii) Draw the Lissajous diagram for these input frequencies.

(ii) Obtain Fx : Fy ratio.

After some changes of vertical input frequency and horizontal input frequency, the

Lissajous diagram become in Figure Q4(c). From Figure Q4(c), determine the phase

difference between vertical input frequency and horizontal input frequency. Given Y1 =

1 cm and Y2 = 1.2 cm.

(8 marks)

Q5 (a) List four advantages of a digital instrument over an analog instrument.

(4 marks)

(b) Figure Q5(b) shows a block diagram of an analog to digital converter (ADC). Give the

name of each component labeled ‘a’ to ‘f’ and sketch the output waveform of the

circuit labeled ‘1’ to ‘5’.

(11 marks)

(c) A constant current of 1 mA is allowed to pass through an unknown resistor, Rx to

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BEE 2123

determine its resistance. The voltage drop across the resistor is applied to a voltage-to-

frequency ADC shown in Figure Q5(c) with a voltage and frequency constant of 0.002.

If the output from the ADC causes 1680 pulses to be stored by the counter during a 0.1

second gate pulse, find the value of the resistor, Rx.

(5 marks)

(d) Name the 2 modes of operation of an electronic counter. Describe briefly each mode of

operation with the aid of appropriate block diagrams.

(5 marks)

Q6 (a) Give the definition and function of electrical transducers.

(5 marks)

(b) Name the three types of transducers then explain the application and function of each

with the aid of appropriate diagrams and equations.

(12 marks)

(c) A Wheatstone bridge strain gauge is excited by a 9 V dc source. When it is stimulated,

each element changes resistance by a value 0.023R and all four arms have equal

resistance R under zero-stimulus conditions.

(i) Draw the Wheatstone bridge strain gauge circuit.

(ii) Calculate the output voltage Eo for 1, 2 and 4 active elements.

(8 marks)

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BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007

PENGALATAN DAN PENGUKURAN ELEKTRIK

KURSUS

KOD MATAPELAJARAN

:

:

BEP, BET, BEM, BER, BKL, BTRBEE2123

Rajah S1(a)/Figure Q1(a)

Rajah S1(b)/Figure Q1(b)

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BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007


KURSUS

KOD MATAPELAJARAN

:

:


Rajah S1(c)/Figure Q1(c)


13

BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007


KURSUS

KOD MATAPELAJARAN

:

:




14

BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007


KURSUS

KOD MATAPELAJARAN

:

:


Rajah S4(a)/Figure Q4(a)


15

BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007


KURSUS

KOD MATAPELAJARAN

:

:




16

BEE 2123

PEPERIKSAAN AKHIR

SEMESTER/SESI

MATAPELAJARAN

:

:

I/2006/2007


KURSUS

KOD MATAPELAJARAN

:

:


Rajah S5(c) / Figure Q5(c)

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bee 2123 final bi asma (modul)

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