NEW
Font size
WorksheetsPSP Diagnostic Quiz
Total questions: 50
Worksheet time: 17mins
Which part of a DC machine houses the field winding?
Armature
Stator
Commutator
Rotor
The primary role of a commutator in a DC generator is to:
Maintain a constant current
Convert AC to DC
Improve efficiency
Control voltage
What is the main purpose of interpoles in DC machines?
Reduce armature reaction
Increase efficiency
Reduce losses
Provide insulation
The efficiency of a transformer at full load is typically:
70-75%
80-85%
95-98%
50-55%
In a DC motor, back EMF is generated in:
Field winding
Armature winding
Rotor core
Commutator
The synchronous speed of a 4-pole induction motor supplied with 50 Hz is:
750 RPM
1500 RPM
3000 RPM
1000 RPM
What type of DC generator is commonly used for arc welding?
Series generator
Shunt generator
Compound generator
Permanent magnet generator
A squirrel-cage rotor is commonly used in:
DC motors
Synchronous motors
Induction motors
Stepper motors
In a transformer, the no-load current:
Lags the applied voltage by nearly 90°
Leads the applied voltage by nearly 90°
Is in phase with the voltage
Opposes the voltage
The main advantage of a 3-phase induction motor over a single-phase motor is:
Higher efficiency
Simpler construction
Self-starting capability
Lower cost
Which of the following motors has the highest starting torque?
DC shunt motor
DC series motor
Induction motor
Synchronous motor
The load on a transformer is increased. The primary current will:
Increase
Decrease
Remain unchanged
Oscillate
The direction of rotation of a DC motor can be reversed by:
Interchanging the field terminals
Reversing the supply voltage
Interchanging armature terminals
Either A or C
In a synchronous motor, the excitation controls:
Speed
Power factor
Torque
Efficiency
The core loss in a transformer consists of:
Hysteresis loss only
Eddy current loss only
Both hysteresis and eddy current loss
None of the above
Which machine is commonly used as a starter generator in aircraft systems?
DC motor
Synchronous motor
Compound generator
Universal motor
In a DC shunt motor, the speed is:
Directly proportional to the load
Nearly constant
Inversely proportional to the voltage
Proportional to the square of the current
Which machine operates on the principle of mutual induction?
Transformer
DC motor
Synchronous motor
Induction motor
The maximum torque of an induction motor is known as:
Pull-in torque
Starting torque
Pull-out torque
Slip torque
The open-circuit test of a transformer measures:
Copper loss
Core loss
Efficiency
Voltage regulation
In a purely resistive AC circuit, the phase angle between voltage and current is:
0°
90°
180°
45°
Which of the following does not change in a transformer?
Voltage
Current
Power
Frequency
In a series RLC circuit, resonance occurs when:
Resistance equals capacitance
Inductive reactance equals capacitive reactance
Inductive reactance is zero
Capacitive reactance is zero
The time constant of an RL circuit is given by:
R/L
L/R
R×LR
L/2RL
The RMS value of a sinusoidal voltage Vm is:
0.707Vm
1.414Vm
2Vm
0.5Vm
In an AC circuit, reactive power is measured in:
Watts
Volt-amperes reactive (VAR)
Volt-amperes (VA)
Ohms
The impedance of a series RC circuit is given by:
R+XcR
R^2+Xc^2
\sqrt{R^2 + X_c^2}
R/Xc
In a parallel LC circuit at resonance, the total current is:
Maximum
Minimum
Zero
Infinite
The angular frequency of an AC circuit is given by:
ω=2πf
ω=2π/f
ω=f/2π
ω=f^2/2π
A diode in an AC circuit is primarily used for:
Amplification
Rectification
Filtration
Voltage regulation
Power factor is defined as the ratio of:
Reactive power to apparent power
Real power to apparent power
Apparent power to real power
None of the above
What happens to the capacitive reactance when the frequency increases?
Increases
Decreases
Remains constant
Becomes infinite
The Q factor of a series RLC circuit is a measure of:
Bandwidth
Quality of resonance
Impedance
Current
In a purely capacitive circuit, the current leads the voltage by:
0°
90°
180°
45°
The total power in an AC circuit is the sum of:
Active power and apparent power
Active power and reactive power
Reactive power and apparent power
None of the above
The voltage regulation of a transformer is defined as the change in secondary voltage when:
The primary voltage changes
The load is disconnected
The load varies from no-load to full-load
The power factor changes
In a single-phase induction motor, the starting torque is:
Zero
Maximum
Equal to the running torque
Dependent on the supply voltage
A universal motor can operate on:
DC only
AC only
Both AC and DC
None of the above
Which type of transformer is used for electrical isolation?
Step-up transformer
Step-down transformer
Isolation transformer
Auto-transformer
In a synchronous generator, the frequency of the generated voltage depends on:
Field current
Armature resistance
Rotor speed and number of poles
Load impedance
The direction of rotation of a single-phase induction motor can be reversed by:
Reversing the main winding terminals
Reversing the auxiliary winding terminals
Both A and B
Changing the supply frequency
A stepper motor is commonly used in:
Power generation
Servo systems
Precision control applications
Conveyor belts
In a DC motor, the torque is proportional to:
Armature current
Square of the field flux
Product of field flux and armature current
Voltage squared
The average value of a sinusoidal current over a full cycle is:
Zero
RMS value
Peak value
0.707×Peak value
In a purely inductive circuit, the power consumed is:
Maximum
Zero
Half the reactive power
Equal to the apparent power
Which of the following increases in a series RLC circuit at resonance?
Current
Impedance
Resistance
Reactance
The power factor of a purely capacitive circuit is:
0
1
-1
0.5
What is the purpose of a choke in a fluorescent lamp circuit?
To increase power factor
To reduce current
To provide a high voltage for starting
To dissipate heat
For a parallel RC circuit, the current drawn from the source is:
In phase with the voltage
Leading the voltage
Lagging the voltage
Zero
The main disadvantage of an autotransformer is:
Higher cost
No electrical isolation between primary and secondary
Poor efficiency
Larger size
