1. What is measurement? Why do we need instruments to measure? Enumerate and define factors that will influence your choice of measuring instruments.
2. Briefly explain the importance of measurement in the following;
i. Scientific research
ii. Industrial production
iii. Automatic control system
3. A beaker weighs 47.21g and a graduate cylinder is used to deliver 22.5ml water to the beaker at 270C. Afterwards, the mass of the beaker and water sample together have a mass of 70.15. What volume is the true volume of water delivered by the graduated cylinder? (Given that, the density of water at 270C is 0.99654g/ml), also determine the percentage error of the measurement by the measuring cylinder.
4. Complete the table below:
Quantity
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Dimension
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SI unit
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Equivalent Unit
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Speed or velocity
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LT-1
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ms-1
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None
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Frequency
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Hertz
|
||
Acceleration
|
|||
Force
|
|||
Work or energy
|
|||
Power
|
5. Explain with a block diagram the basic components of electrical measuring system.
6. Describe forces/device required in the operation of an analogue indicating instrument.
7. With a suitable diagram, explain the principle of operation of an attraction and repulsion types of moving-iron instrument.
8. Describe how a moving-coil instrument can be improved to indicate the amplitude of an alternating signal.
9. Define the following in terms of their operation/use;
(i) Ammeter (ii) Voltmeter (iii) Shunt resistance (iv) Multiplier resistance
(v) Multirange meter.
10. Design a multirange ammeter by using direct method to measure within the following ranges. 10mA, 100mA, 1A and 10A. With a Permanent Magnet Moving Coil (PMMC) meter of internal resistance of 100W and full scale current of 1mA.
11. What do you understand by ‘Null method of measurement’. Describe with the aid of an appropriate diagram, the following Null methods of measurement;
(a) Wheatstone bridge (b) D.C potentiometer
12. A d.c potentiometer is balanced when the slider is at 380mm using a standard cell of 1.242Volts. Determine the electromotive force (e.m.f) of a dry cell if balance is obtained with a length of 716mm.
13. In a Wheatstone bridge ABCD, a galvanometer is connected between A and C, and a battery between B and D, a resistor of unknown value is connected between A and B. When the bridge is balanced, the resistance between B and C is 470Ω, that between C and D is 18Ω and that between D and A is 300 Ω. Calculate the value of the unknown resistance.
14. The core of an analogue oscilloscope is a special type of vacuum tube known as a cathode ray tube. With a suitable diagram explain how a CRT functions. What goes on inside the tube to produce waveform displays on the screen?
15. In general electronic use, when measuring AC voltage signals, what do the two axis (horizontal and Vertical) of the oscilloscope screen represents?
16. For the sinusoidal waveform shown figure 16, below, the volt/cm switch is on 50volt/div and time/cm switch is on 5ms/div. Determine;
(a). The frequency (b) The peak-to-peak voltage (c). The root mean square (r.m.s) voltage value of the signal.
Figure 16
17. What do you understand by the phrase; “Temperature of a body”. Convert the following temperature in Celsius scale into Fahrenheit scale; (i) 40.50C (ii) - 200C.
18. Describe briefly the principle of operation of the following temperature sensing instruments (thermometer), (i) Liquid-in-glass thermometer (ii) Bimetallic strip thermometer (iii) Pressure thermometer.
19. In a certain thermocouple, 19.65mV of voltage is observed at its output when the reference junction T1 is maintained at 00C and T2 at 67.30C.
Using the same thermocouple, a potential difference output of 5.87mV was observed, when junction T1 was dipped in a melting ice and junction T2 was inserted in a solution of unknown temperature. Determine the temperature of the solution.
20. Assume a newly produced mercury-in-glass thermometer, to calibrate the thermometer, measurement of increase in mercury thread length in the thermometer against temperature values was taken and tabulated as shown in table 17 bellow;
Table 17:
Change in temperature, Δθ(0C)
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Change in Mercury length, ΔL(mm)
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12.0
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2.16
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22.1
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4.40
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42.8
|
7.70
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51.4
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9.25
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60.5
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16.94
|
i. Plot the graph of the ΔL in the Y-axis against the ΔL against the Δθ0C on the x-axis, hence; determine the sensitivity of the thermometer with the graph.
ii. On another graph sheet, calibrate the thermometer using a suitable scale to measure temperature range 00C – 1000C.
21. (a) Science/Technology depends on data and interrelation of different data types; measurement and quantification of various physical and chemical parameters “begat” data; measurement without proper measuring instruments results in a conjecture unusable for scientific and technological inference. Explain this statement with suitable illustrations.
22. Control system without measurement is “tantamount” to a car without the “steering”. Explain.
23. Explain with a block diagram the basic components of electrical measuring system.
24. With a suitable diagram, explain the principle of operation of an atraction and repulsion types of moving-iron instrument.
25. Determine the shunt required to employ a moving-coil instrument of full scale deflection current of 1mA and internal resistance of 25Ω, as an ammeter to measure current range of 0-100mA.
26. Describe briefly the principle of operation of the following temperature sensing instruments (thermometer), (i) Liquid-in-glass thermometer (ii) Bimetallic strip thermometer (iii) Pressure thermometer.
27. What is a Cathode Ray Oscilloscope? The core of an analogue oscilloscope is a special type of vacuum tube known as a cathode ray tube. With a suitable diagram explain how a CRT functions. What goes on inside the tube to produce waveform displays on the screen?
28. In general electronic use, when measuring AC voltage signals, what do the two axis (horizontal and Vertical) of the oscilloscope screen represents.
29. A sinusoidal waveform of two voltage signals with the same frequency shown in figure 29, below, the volt/div switch is on 2.5V/div and time/div switch is on 5ms/div. Determine; determine the phase difference between the two signals in degrees.
Figure 29
