LAGOS CITY POLYTECHNIC, IKEJA
SCHOOL OF ENGINEERING AND APPLIED SCIENCE
DEPARTMENT OF ELECT/ELECT AND COMPUTER ENGINEERING
2016/2017 SEMESTER EXAMINATION
COURSE TITLE:
COURSE CODE:
FOR WHOM:
ANSWER
ELECT CIRCUIT THEORY II
NO OF QUESTION :
6
EEC 242/249
TIME
ALLOWED: 2 HRS
ND YR III
CE
PT
INSTRUCTIONS:
ANY
4
QUESTIONS
1.
(a)
series
A 10W Resistor, a 100mF capacitor and an inductor of 0.15H are connected in
to
a
supply at 230v, 50Hz. Calculate the power consumed by the circuit.
(b)
A transfomer has a rated out put of 200KVA with a power factor of 0.6. Calculate
the
following.
(i)
Real
Power
(ii)
Reactive
Power
2.
(a)
system.
Two wattemeter Wi = 8kw and W2 = 4kw are connected to measure power in a
Determine.
(i)
The Total Input power
(ii)
Load power factor
(b)
With the aid of a diagram, explain the reaction of power in the following circuit.
(i)
Resistance
Circuit
(ii)
Inductive cct
(iii) Capacitance
3.
(a)
a.b.c.
30
An unbalanced star-connected load has balanced phase voltage of 120v and the
sequence. The line currents are given as Ja = 10<0oA, Jb = 20< -40o Jc >=
<-155A.
Find
the
power
consumed
by
the
circuit
(b)
100,000W
An 20mF capacitor is charged to a p.d of 400v and then discharged through a
resistor.
Determine
(i)
Time constant
(ii) initial value of discharged current
circuit
4.
(a)
A machine is connected to a 240v a.c supply and draws a current of 18A at a
power
factor
of
0.7.
Calculate
the
power
consumed.
5.
of
(b)
Explain
power
(i)
Sketch
Two
(a)
A coil having 10W resistance and 14H inductane is connected across a d.c voltage
140v,
after the current has reached its final value, how much time would it take for the
to
reach
a
value
of
8A
after
switching
off
the
supply.
current
6.
growth
measurement
out
of
curve
and
circuit
in
a
THREE
the
(ii)
decay
RL
3o
diagram
curve
system
above.
(b)
Sketch
the
(i)
RC
for
the
circuit
(a)
The impedance per phase of a delta connected load is 10W perphase, the line