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Cork Institute of Technology
Higher Certificate in Engineering in Biomedical Engineering-Stage 1
(National Certificate in Engineering in Biomedical Engineering-Stage 1)
NFQ- (Level 6)
Autumn 2005
Biomedical Devices & Instrumentation
(Time: 3 Hours)
Answer FIVE questions.
Two from Section 1 & Three from Section 2
All questions carry equal marks (20%)
Examiners: Mr. M.J. Howard Mrs. M. Uppal Dr. D. Tallon Prof. P. McHugh
Section A: Electro-Technology
Q1. (a) Give the SI units of the following physical quantities: i. Electrical Current ii. Electric Potential iii. Electromotive force, ε.m.f
(b) What instruments would you use to measure the following physical quantities, in each case show with the aid of a diagram how the instrument should be connected to make each measurement: i. Potential Difference across a bulb in a circuit ii. Potential Difference across a resistor in a circuit iii. The current flowing through a circuit
(c) Why can static electricity be a nuisance? Give three examples of when static electricity can be a hazard. How is the build up of static electricity prevented?
(d) Define the term capacitance and state the SI units.
(e) With the aid of a diagram, briefly explain how a parallel plate capacitor “stores” charge? What precautions are essential when connecting an electrolytic capacitor into a circuit? (20 Marks)
Q2. (a) State Ohm’s Law defining each symbol used. (b) What is the relationship between current and charge? (c) A 20 Ω resistor is connected in parallel with a 15 Ω resistor and the combination is then connected in series with a 10 Ω resistor. This combination of resistors is connected to a 12 V battery (of negligible internal resistance) in a circuit:
i. Sketch the circuit diagram. ii. Calculate the total effective resistance in the circuit. iii. Calculate the current from the battery. iv. Calculate the current through each resistor v. Calculate the power dissipated in each resistor (20 Marks)
Q3. (a) Define electric field strength and state the equation that gives the electric field strength created by a point charge, explaining all symbols used. (b) Sketch the pattern of lines of electric force created between two equal and opposite electric force point. (c) Calculate the electric force between a proton and an electron at a separation of 1.0 nm. A proton carries a charge = +1.6 x 10 -19^ C and an electron has a charge = - 1.6 x 10-19^ C. State whether they would move towards or away from each other due to this force. (d) How will the magnitude of the electric force calculated above change, if the distance between the two point charges is halved? (ε 0 = 8.85 x 10-12^ Fm-1) (20 marks)
(c) Find the Mass Flowrate (Fm) in a water main if the water is flowing at a rate of 7.04 m/s and the diameter of the main is 90mm. (Water density is 1000kg/m^3 ). Hence, determine the percentage change of the Mass Flowrate if the water density changes to 997kg/m^3? (8 marks)
Q7. (a) It is required to use an existing meter installation consisting of an Electromagnetic
Flowmeter, to measure in the range of 200cm^3 /s to 20000cm^3 /s volumetric flowrate (Q). Determine the output voltage range(E) of the meter. Diameter is 50mm and the Flux (B) is 0.10 Tesla. E.M.F. is directly proportional to the speed at which the conductor cuts the lines of flux. (8 marks)
(b) Describe the operation of an Electromagnetic Flowmeter with the aid of a concise diagram and using the following headings: Scientific reasoning, Microprocessor systems and their output signals, liquid conductivity, tube lining material, advantages and disadvantages. (9 marks)
(c) Electromagnetic flowmeters can often experience material deposition on the measuring electrodes. Describe clearly two methods to remove/reduce this deposition. (3 marks)
Q8. (a) Describe the operation and theory of a simple U-tube manometer. Include advantages, disadvantages. (6 marks) (b) The C-type Bourdon tube is very common and was one of the first simple pressure measurement devices. Draw a diagram and explain its operation in full. List accuracy, materials and ranges of these devices. (7 marks) (c) Describe the construction and operation of the Pneumatic Dead Weight Tester. Briefly describe what you know about a Semiconductor Pressure Transducer. (4 marks) (d) Describe three of the five sources of errors in Manometers. (3 marks)
