NAROK UNIVERSITY COLLEGE
(A CONSTITUENT COLLEGE OF MOI UNIVERSITY)
SPECIAL/SUPPLEMENTARY UNIVERSITY
EXAMINATIONS 2010/2011
SECOND YEAR
SCHOOL OF SCIENCE
BACHELOR OF COMPUTER SCIENCE
COURSE CODE: COM 215
COURSE TITLE: ELECTRIC CIRCUITS
DATE:
AUGUST , 2011
TIME: 3 HOURS
INSTRUCTIONS
 Answer Question ONE and any other THREE.
 Use of sketch diagrams where necessary and brief illustrations are encouraged.
 Read the instructions on the answer booklet keenly and adhere to them.
Page 1 of 5
QUESTION ONE: [24 marks]
a) Define the following terms as used in electric circuits
(i) Circuit
(ii) Passive network
(iii) Linear circuit
[3]
b) Explain the meaning of the following terms with the use of a sketch circuit diagram [3]
(i) Node
(ii) Mesh
(iii)loop
c) Determine the currents in the unbalanced bridge circuit of fig 1. Determine the p.d. across BD and
the resistance (all resistances are in ohms) from B to D
[4]
Fig 1.
d)
Use nodal analysis to determine the voltage across 5 ohm resistor and the current through the 12 V
source in fig 2. [4]
Fig 2.
Page 2 of 5
e) Using superposition theorem, find the current through the 40 Ω resistor of the circuit shown in Fig.
3 . (all resistances are in ohms) [4]
f) A total current of 10 A flows through the parallel combination of three impedance : (2-5j)Ω, (6 + 3j)
Ω, and (3 + 4j) Ω. Calculate the current flowing through each branch. Find also the p.f of the
combination. [6]
QUESTION TWO: [12 marks]
a) State the Norton theorem
[3]
b) Use Norton’s theorem to determine the current flowing in the 10 Ω resistor for the circuit shown in
figure 4. [9]
Fig 4
QUESTION THREE: [12 marks]
a) State the superposition principle
[3]
b) For the circuit shown in figure 5 , find, using the superposition theorem,
(i)
the current flowing in and the voltage across the 18 Ω resistor,
[5]
(ii)
the current in the 8 V battery and (c) the current in the 3 V battery. [4]
Page 3 of 5
Fig 5.
QUESTION FOUR: [12 marks]
a) Explain one application of the maximum power transfer.
[2]
b) Determine, for the network shown in Figure 6,
(i) the values of R and X that will result in maximum power being transferred across terminals
AB, and
[5]
(ii) the value of the maximum power. [5]
Fig 6.
QUESTION FIVE:
[12 marks]
a) Distinguish between apparent power and reactive power in a.c apparatus
[3]
b) A current of (15 + j8)A flows in a circuit whose supply voltage is (120 + j200)V. Determine
(i) the active power, and
[5]
Page 4 of 5
(ii) the reactive power.
QUESTION SIX:
[4]
[12 marks]
a) State the Thevenin’s theorem
[3]
b) For the circuit shown in figure 7, use Thevenin’s theorem to determine
(i)
the current flowing in the capacitor, and
(ii)
the p.d. across the 150 kΩ resistor.
Fig 7.
End and Good Luck.
Page 5 of 5
[5]
[4]