CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2007/08
Module Code:
School:
Programme Title:
Programme Code:
ELTR 6007
Electrical & Electronic Engineering
Bachelor of Engineering (Hons) in Electronic Engineering – Year 1
EELXE_8_Y1
External Examiner(s):
Internal Examiner(s):
Instructions:
Prof. G. Hurley
Dr. S. Foley
Dr. M. Cranitch
Answer Question 1 and two other questions.
Duration: 2
Sitting: Winter 2007
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper.
If in doubt please contact an Invigilator.
1 ELTR

Q1. (a) State Kirchoff’s Laws in relation to both current (KCL) and voltage (KVL). Include a diagrammatic sketch and equation in each case. [10 Marks]
(b) Explain the difference between an insulator and a conductor. Give an example of both types of material. [5 Marks]
(c) With the aid of relevant circuit diagrams, distinguish between a voltage divider and a current divider. [5 Marks]
(d) Define the term ‘time constant’ in relation to the charging of a capacitor. With reference to the time constant, how long does it take to charge a capacitor fully? [5 Marks]
(e) Sketch the curve implied in the expression for the instantaneous voltage on a charging capacitor, v = V(1 − e t/T ). Explain the shape of the curve. [5 Marks]
(f) With regard to magnetism, explain what is meant by the terms ‘permeability’ and
‘relative permeability’. [5 Marks]
(g) A house has twenty-two 100W lights all of which run continuously for eight hours every day. The electricity supply is 220V. (i) Calculate the total current when all the lights are operating. (ii) Determine the annual lighting bill for the house if 1kWh of electricity costs
14.35 cent. (iii) Calculate the yearly saving on the bill if the lights are replaced by energy-efficient CFL bulbs having the same light output but rated at 23W. [15 Marks]
Q.2 Using either the mesh or node analysis method, determine the values of I
1
, I
2
, I
3
for the circuit shown in the following diagram:
[25 Marks]
2 ELTR

Q.3 (a) Two capacitors with values of 6 µ F and 12 µ F, respectively, are connected in series across a direct voltage supply of 120V. For each capacitor, determine the voltage and charge, as well as the energy stored. [12 Marks]
(b) A capacitor of 10 µ F is connected in series with a resistor of 1k Ω across a 100V direct supply. Determine (i) the time constant, (ii) the initial charging current, (iii) the voltage on the capacitor after 10 ms, and (iv) the time taken for the capacitor to charge to 90% of its final value. [13 Marks]
Q.4 (a) With reference to the magnetisation of an iron core, draw a typical B-H curve. [5 Marks]
(b) Explain the shape of the curve in part (a), with particular reference to the term
‘hysteresis’. [5 Marks]
(c) Give an ‘everyday’ example of the application of hysteresis, other than in relation to magnetism. [5 Marks]
(d) Draw up a table of comparison between a magnetic circuit and an electric circuit. Refer to one important aspect in which the circuits differ. [10 Marks]
3 ELTR