Birla Institute of Technology & Science, PilaniWork-Integrated Learning Programmes Division

First Semester 2010-2011Mid-Semester Test (EC-1 Regular)

Course No. : ENGG ZC111 Course Title : ELECTRICAL & ELECTRONICS TECHNOLOGY Nature of Exam : Closed Book Weightage : 40% Duration : 2 Hours Date of Exam : 29/08/2010 (AN) Note: 1. Please follow all the Instructions to Candidates given on the cover page of the answer book.2. All parts of a question should be answered consecutively. Each answer should start from a fresh page. 3. Mobile phones and computers of any kind should not be used inside the examination hall. 4. Use of any unfair means will result in severe disciplinary action.

Q.1. Find the voltage across the 4Ω resistor in the network shown in Fig. Q.1 using (a) Nodal analysis (b) The superposition theorem (c) Thevenin’s theorem [15]

Figure Q.1

Q.2. The power dissipation across and the current in a circuit are represented by (100+j200) V and (10+j5) A respectively. Calculate the active power and the reactive power. [4]

Q.3. A parallel network consists of branches A, B and C. If IA=10 -60o A, IB=5 -30o

A, and IC=10 90o A, all phase angles, being relative to the supply voltage, determine the total supply current. [7]

Q.4. A 100 kVA transformer has 400 turns on primary and 80 turns on secondary. The primary and secondary resistances are 0.3 Ω and 0.01 Ω respectively, and the corresponding leakage reactances are 1.1 Ω and 0.035 Ω respectively. The supply voltage is 2200V. Calculate the per-unit and the percentage resistance and leakage reactance drops of the transformer. [7]

Q.5. A coil having a resistance of 8 Ω and a constant inductance of 4 H is connected

across a 40 V dc supply. Calculate 5.1. The time constant5.2. The final value of current5.3. The value of current 2 s after it is connected to supply5.4. The time taken by current in circuit to grow 4.32A after it is connected to

supply. [7]

No. of Pages = 1No. of Questions = 5

2V

2A