ABRAHAM ADESANYA POLYTECHNIC, IJEBU-IGBO FIRST SEMESTER EXAMINATION NDI 2016/2017 SESSION SCHOOL OF ENGINEERING .......................................................................................................................................... COURSE TITLE: COURSE CODE: LEVEL: INSTRUCTION: ELECTRICAL ENGINEERING SCIENCE 1 EEC115 TIME: 2:00 HRS ND I ELECTRICAL/ELECTRONIC ENG. & COMPUTER ENGINEERING ANSWER ANY FIVE QUESTION 1a. Define energy and state its various form 6mks 2 b. The power expended in a certain resistor is given by I R. If the power expended in the resistor is 175W when the current is 5A, Calculate the power in the resistor when, (i) Both current & resistance are double. (ii) Current is half and resistance double. (iii) When current is double and resistance half. 8mks 2a. Define the following terms and state the unit in which they are measured: (i)Electric current (ii)Potential Difference (iii)Electromotive force (iv)Resistance 8mks b. Two metre resistance wire of cross sectional area of 0.5mm2 has a resistance of 2.2Ω. Calculate (i) the resistivity of the material (ii)the length of the wire which when connected in parallel with the 2m length, will give a resistance of 2.0 Ω 6mks 3a. Define Capacitance of a capacitor and list the different types 4mks b. Two capacitors, A and B, of capacitance 2µF and 4µF respectively, are connected in series to a dc supply; the charge store by each capacitor is 0.16mc. Determine: (i) the p.d across each capacitor (ii) the energy stored in each capacitor (iii)the effective capacitance of the series combination. 10mks 4a. State five analogies between water flow and current flow 5mks b. A circuit consists of a 1 Ω wire in series with a parallel arrangement of 6 Ω and 3 Ω and a p.d of 12V is connected across the whole circuit. Calculate the current in each of the 3 wires and the p.d across each using ohms law 9mks 5a. For the network shown in Fig.below, find the values of the currents marked 126 5mks b. State kirchoff’s laws c. Differentiate between conductor, insulator and semiconductor 4mks 5mks 6a. Define the following terms (i)Electric field strength (ii)Electric flux density (iii)Electric potential (iv)Electric field 8mks -9 -9 b. The small identical conducting spheres have charges of 2.0 × 10 and -0.5 ×10 respectively. When they are placed 4 cm apart, what is the force between them ? If they are brought into contact and then separated by 4 cm, what is the force between them ? 6mks 7a. State the coulomb’s laws of electrostatic 4mks b. If two batteries are connected in parallel, one of EMF 6V and internal resistance 0.5Ω and the other of EMF 8V and internal resistance 0.6Ω, and in turn connected to an external 10Ω resistor. Find the current in each resistor using kirchoff’s laws 10mks 127