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WorksheetsElectrical MCQ
Total questions: 45
Worksheet time: 23mins
Ohm’s law is valid for:
AC only
DC only
Both AC and DC
Neither Ac nor DC
Unit of electrical power is:
Volt
Watt
Ohm
Ampere
1 HP (Horsepower) = ?
746 W
1000 W
748 W
748 W
4. The resistance of a wire is directly proportional to:
Length
Cross-sectional area
Temperature
All of the above
Which instrument is used to measure current?
Voltmeter
Ammeter
Watt mater
Ohm metter
Power factor of a pure resistor is:
0
1
0.5
-1
In a DC circuit, the frequency is:
50 Hz
0 Hz
15 HZ
Infinity
Which of the following is not a type of power in AC circuit?
Apparent power
True power
Reactive power
Linear power
A capacitor blocks
DC only
Ac only
Both AC and DC
None
In an RLC circuit, resonance occurs when:
XL = XC
R = 0
XL > XC
XC > XL
The frequency of rotor current in an induction motor is:
Same as supply frequency
Zero
Depends on slip
Constant
Transformer works on the principle of:
Electrostatics
Electromagnetic induction
Thermionic emission
Coulomb’s law
Which part of the transformer does not move?
Rotor
Armature
Stator
All parts are stationary
Which motor is commonly used in ceiling fans?
Universal motor
DC motor
Single-phase induction motor
Synchronous motor
In an RLC series circuit at resonance, the current is:
Minimum
Maximum
Zero
Depends on R only
a transformer, core losses depend primarily on:
Frequency and flux density
Current
Voltage
Power factor
The function of a commutator in a DC machine is:
Convert AC to DC
Reverse the direction of current
Convert DC to AC
Provide insulation
Ferranti effect occurs in:
Induction motors
Transformers
Long transmission lines at no load
Short transmission lines at full load
In a 3-phase system, the power factor is 0.5 lagging. The effect of adding a capacitor bank is to:
Increase power factor
Decrease power factor
Reduce active power
Reduce frequency
The synchronous speed of a 4-pole alternator operating at 50 Hz is:
1550 RPM
1400 RPM
1500 RPM
1000 RPM
If slip of an induction motor is 0, the rotor speed is:
Synchronous speed
Zero
Half of synchronous speed
Infinite
Two resistors of 10 Ω and 20 Ω are connected in parallel. The equivalent resistance is:
6.67 Ω
30 Ω
15 Ω
10 Ω
In a transformer, the maximum flux in the core depends on:
Number of turns only
Frequency only
Applied voltage and frequency
Load current
In a power system, ferranti effect is more prominent when
Transmission line is short
Load is capacitive
Load is inductive
Line is lightly loaded or open at receiving end
For a 3-phase unbalanced load, the wattmeter method that gives accurate power is:
Two wattmeter
One wattmeter
Cannot be measured
Three wattmeter
A 3-phase squirrel cage induction motor starts with:
Zero torque
High starting torque
Low torque
Torque depending on load
The skin effect in conductors increases with:
Lower frequency
Higher frequency
Lower diameter
Higher resistivity
The core loss in a transformer at no load is represented by
Series resistance
Shunt resistance
Leakage reactance
Series inductance
The magnetizing current in a transformer lags the voltage by:
0°
90°
180°
45°
The direction of rotation of a universal motor can be reversed by:
Reversing armature terminals only
Reversing supply polarity
Reversing either armature or field connections
Cannot be reversed
Transformer oil is mainly used for:
Conducting
Lubrication
Cooling and insulation
Increasing efficiency
The zero-sequence current does not flow in:
Y-connected with neutral grounded
Delta connected system
Single-phase circuit
Unearthed system
Thevenin's theorem is applicable for:
Only resistive circuits
Only linear bilateral networks
Only nonlinear networks
All types of circuits
In a pure inductive circuit, the average power consumed is:
Maximum
Equal to apparent power
Minimum but not zero
Zero
For maximum power transfer in AC circuit, load impedance must be:
Equal to source impedance
Equal to conjugate of source impedance
Greater than source impedance
Less than source impedance
A salient pole alternator has:
Non-uniform air
Uniform air gap
No poles
Used only in 1-phase
Which instrument has the same scale for both AC and DC?
MI
PMMC
Electrostatic
MC
In a synchronous generator, hunting is reduced by:
Laminated core
Cooling system
Damper windings
Increase field current
In which part of the generator is voltage induced?
Field winding
Brush
Shaft
Armature winding
If a synchronous motor runs at 1000 RPM and is connected to 50 Hz supply, the number of poles is:
2
4
6
8
If the efficiency of a transformer is maximum, then:
Core loss = Copper loss
Copper loss = Zero
Core loss > Copper loss
Copper loss > Core loss
The torque-speed characteristic of a DC shunt motor is:
Almost constant speed
Linearly increasing
Linearly decreasing
Exponential
If frequency increases in an AC circuit, capacitive reactance:
First increases, then decreases
Increases
Remains constant
Decreases
Which of the following is NOT a function of a circuit breaker?
Protecting the circuit
Breaking circuit under load
Detecting fault
Isolating fault
In power transmission, bundled conductors are used to:
Reduce resistance
Reduce corona loss
Reduce inductance only
Increase capacitance only
