Winter 2012 Exams for ELEC 6018 in Cork Institute of Technology, Exams of Electrical Engineering

Download Winter 2012 Exams for ELEC 6018 in Cork Institute of Technology and more Exams Electrical Engineering in PDF only on Docsity! Page 1 of 4 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 1 Examinations 2012/13 Module Title: Electrical Science Module Code: ELEC 6018 School: Electrical & Electronic Engineering Programme Title: Bachelor of Engineering in Electrical Engineering – Year 1 Bachelor of Engineering (Hons) in Electrical Power Systems – Year 1 Programme Code: EELEC_7_Y1 EEPSY_8_Y1 External Examiner(s): Ms Mary Desmond, Mr Colm Murray Internal Examiner: Emmanuel Pican Instructions: Answer all questions. Duration: 2 Hours Sitting: Winter 2012 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination. If in doubt please contact an Invigilator. Page 2 of 4 Q1. a) A 34.5m length of copper wire at 20°C has a radius of 0.25mm. If a potential difference of 9.0V is applied across the length of the wire, determine the current in the wire. You may assume that the resistivity of copper to be 1.7 x 10 -8 Ωm. [10 marks] b) If the wire is heated to 30.0°C and the 9.0V potential difference is maintained, what is the resulting current in the wire? The temperature coefficient of resistance of copper is: 3.9x10 -3 /°C. [10 marks] Q.2 a) 200 litres of water are to be heated in an immersion. The water is at 10° Celsius and is to be heated to 55° Celsius. Calculate the amount of energy that will be needed to heat this amount of water. [10 Marks] b) The water is to be heated within 30 minutes, calculate the rating of the electric element to perform this task. [10 marks] Q3. Instead of buying a capacitor, you decide to make one. Your capacitor consists of two circular metal plates, each with a radius of 5 cm. The plates are parallel to each other and separated by a distance of 1 mm. The permittivity of air is 8.85x10 -12 F/m. You then connect a 9 volt battery across the plates, find: a) the capacitance of the capacitor. [8 marks] b) the charge on each plate. [8 marks] c) the excess number of electrons on the negative plate. [4 marks]