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Total questions: 44
Worksheet time: 15mins
The condition in Ohm’s Law is that:
ratio V/I should be constant
current should be proportional to voltage
temperature must be constant
temperature should vary
The resistance of carbon when its filament temperature is decreased
increases
decreases
remains the same
increase enormously
It was experimentally found by James Prescott Joules that the heat produced in a current carrying conductor is proportional to:
the square of current
square of resistance
the current
inversely proportional to time
The presence of electric current is made known by:
flashing
effects produced
cracking
electric shock
The resistance R1 and R2 are in parallel. The ratio of the value of resistance R1:R2 is 4:1. The currents in R1:R2 will be equal to:
1:4
1:1
4:1
4:4
Four resistances are connected in series such that R1>R2>R3>R4 and supplied by a 110V source. The least power consumption will be in:
R1
R2
R3
R4
Three resistances are connected in series with a 220V supply. If R2 becomes open-circuited, the reading of the voltmeter will:
become 220V
decrease slightly
fall to zero
increase slightly
What is the formula for Maximum Power Transfer or Pmax?
V2/ 4R2
V2 / 4R
V2/ R
V2/ 2R
In the case of delta-connected circuit, when one resistor is open, the power will be:
unaltered
reduced to 1/3
reduced to 1/9
reduced to 1/6
What will happen to the reactance of the capacitor when the capacitance is reduced by 25%?
increase by 25%
increase by 33%
increase by 50%
. increase by 75%
What are the minimum requirements to cause the flow of electric current?
a voltage source, an ammeter, a conductor and insulator
a voltage, source, a switch and a resistor.
a voltage source and a conductor
a voltage source, a conductor and an insulator
In a series connection of bulb A and B and a source, bulb B grows brighter because its resistance is
in parallel with A
in series with A
lower than A
higher than A
Which of the following is non-linear element?
diode
transistor
heater coil
electric arc with unlike diode
For differential protection, how are the current transformers of the distribution transformer are connected wye-delta?
delta-wye
delta-delta
wye-wye
open delta-wye
A series RLC circuit has R=1Ω, L=0.5H and C= 0.5F. What is the resulting transient current?
undamped
overdamped
critically damped
underdamped
If a positive sequence current passes through a transformer and its phase shift is 30 degrees, the negative sequence current flowing through the transformer will
30 deg
-30 deg
120 deg
0 deg
Expanded ACSR conductors are used
To increase the tensile strength of the line
To reduce corona loss
To reduce I2R loss
To minimize galloping
The surge impedance of a double-circuit power transmission line is
40 ohms
200 ohms
400 ohms
800 ohms
The percentage regulation of an overhead transmission line can be zero when the load power factor is:
Lagging
Unity
Leading
zero
What is the time at which the load is disconnected when there is fault?
arcing time
melting time
cut-off time
operating time
The interrupting capacity of circuit breaker is generally determined by:
line to ground fault
symmetrical fault
asymmetrical fault
line to line fault
A device that connect the conductor to the earth to discharge the charge on the earth
surge arrester
grounding electrode
dissipator
earthing switch
When extra stop buttons are added to an existing starter control circuit, they must be:
in parallel to the start button
in series with the motor
in parallel to overload
in series with contactor coil
What is the device number for distance relay?
52
22
51
21
What is the type of communication that only one of the two party can transmit at a time?
full duplex
half duplex
bicomm
simplex
Cooling of 500 MW turbo-generators is usually done by the following coolants
Nitrogen & hydrogen
Hydrogen & water
Carbon dioxide & hydrogen
Water only
Pumped storage hydroelectric plant can be operated with
Upstream reservoir only
downstream reservoir only
with both as above
none of the above
Running cost of a hydro plant with respect to that of a thermal plant is
More
Less
varying from installation to installation
equal
Pick up the odd plant from the following
Steam
Wind turbine generator plant
Tidal
Solar
Governor is used with the steam turbine to regulate
Steam temperature
Steam pressure
Power output
Speed
A zero sequence relay responds to:
L-G fault
L-L fault
3-phase fault
SLG fault
The synchronous reactance of a modern large size turbo generator in pu is nearest to
1
2
3
4
The base value of a power system is chosen based upon
the rating of one machine in the system
the largest machine in the system
some average (rounded) values such that the pu machine ratings are not too large or too small
Base voltage
Peak load hydro power plants compared to base load thermal plants have plant capacity factor
Much lower
Much higher
Almost equal
Always constant
Heavy water in a nuclear reactor is used for
Cooling & moderation
Cooling and shielding radiation
Moderation & shielding radiation
Moderation only
In reverse PN junction, with the voltage is increasing, the current is
increasing
decreasing
increasing exponentially
no change
An ACSR conductor of size 48/7 means that:
it has 48 strands of steel and 7 strands of aluminum
it has 7 strands of steel and 48 strands of aluminum
it has 48 strands of copper and 7 strands of aluminum
it has 7 strands of copper and 48 strands of aluminum
The following are the essential parts of a hydroelectric power station EXCEPT:
spiral case
impeller
surge tank
throttle valve
What is the minimum diameter of grounding rod?
15mm
10mm
16mm
13mm
Plate electrode shall be installed not less than ____mm below the surface of the soil
600
450
750
240
Where is the surge arrester best installed?
near to transformer
near to air switch
near to busbar
near to isolator
The type of switchgear assembly commonly selected for use in a turbine generator power plant:
dual benchboard
vertical switchboard
duplex benchboard
enclosed switchboard
A certain length of wire with resistance R is divided into 3 equal lengths. It is placed side by side. What is the new resistance of the wires?
R/9
R/27
R/3
R
