Dgca Module 03 Electrical Fundamentals
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- 1.In what equipment is a photon radiated when an electron leaves a hole?.
- A.
Photo-cell.
- B.
LED.
- C.
Photo diode.
- 2.Elements such as phosphorus with 5 electrons in their outer shell, when combined with pure silicon, is a.
- A.
Isotopic.
- B.
Acceptor.
- C.
Donor.
- 3.An atom with less than 4 electrons in its outer shell has.
- A.
Low electrical resistance.
- B.
No electrical resistance.
- C.
High electrical resistance.
- 4.Two inductive coils are placed in close proximity with each other at 90 degrees. The number of flux linkages is.
- A.
0
- B.
Maximum negative.
- C.
Maximum
- 5.Three inductors 10 mH, 5 mH and 20 mH are connected in parallel. What is the total inductance?.
- A.
Without knowing the coupling factor the total inductance cannot be found.
- B.
2.86mH
- C.
35mH
- 6.The time constant of an inductor is.
- A.
L/R
- B.
L2 /R.
- C.
LR.
- 7.If the rate of change of current is halved, mutual inductance will_______
- A.
Stay the same
- B.
Halve
- C.
Double
- 8.When more than two inductors of different inductance are connected in parallel in a circuit, the total inductance is.
- A.
Equal to the sum of the individual inductance.
- B.
Equal to the inductance of the highest rated inductor.
- C.
Less than the inductance of the lowest rated inductor.
- 9.The time constant in an inductive circuit is the time required for the current to reach.
- A.
70.7% of maximum value
- B.
63.2% of maximum value
- C.
63.7% of maximum value
- 10.An induced current in a coil.
- A.
Opposes the EMF producing it.
- B.
Does not affect the EMF producing it.
- C.
Aids the EMF producing it.
- 11.Capacitance is _________ to plate surface area.
- A.
Directly proportional
- B.
Inversely proportional
- C.
Same
- 12.Which Of the below statement is true 1. Inductance is more, More no of flux lines 2. Inductance is less, Less no of flux lines 3. Inductance is more, Less no of flux lines
- A.
Both 1 and 3 true
- B.
Both 1 and 2 are true
- C.
Only 1 is true
- 13.In thermister, if temperature increases its resistance ___________
- A.
Increases
- B.
Decreases
- C.
Remain same
- 14.Unit of power is
- A.
Joule
- B.
Joule/sec
- C.
Joule/min2
- 15.An inductor is said to be saturated when.
- A.
The current is at a maximum
- B.
The current through it is zero
- C.
It will no longer accept lines of flux.
- 16.In a DC motor, the stator's magnetic field, due to armature reaction, moves.
- A.
In the same direction of rotation of the armature.
- B.
In the opposite direction of rotation of the armature.
- C.
Into alignment with the GNA.
- 17.A small air gap between magnetic poles results.
- A.
In a weaker field than a large air gap, for the same magnetising force.
- B.
In a stronger field than a large air gap, for the same magnetising force.
- C.
In the same field as a large air gap, for the same magnetising force.
- 18.Decreasing the field current in a shunt motor will.
- A.
Decrease speed and increase torque.
- B.
Increase speed and increase torque.
- C.
Increase speed and decrease torque.
- 19.To calculate generator output you need to know the.
- A.
Armature speed and number of series conductors.
- B.
Armature speed and field strength.
- C.
Armature speed and number of parallel conductors.
- 20.In a shunt motor, if you reverse both field current and the armature current, the motor will.
- A.
Stop.
- B.
Change direction.
- C.
Continue to run in the same direction.
- 21.If a generator speed is halved and the field strength is doubled, the voltage output will be.
- A.
Unchanged.
- B.
Doubled.
- C.
Halved.
- 22.How can the direction of rotation of a DC electric motor be changed?.
- A.
Reverse the electrical connections to either the field or armature windings.
- B.
Rotate the positive brush one commutator segment.
- C.
Interchange the wires which connect the motor to the external power source.
- 23.The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the.
- A.
Rotates speed at which the armature
- B.
Strength of the magnetic field.
- C.
Number of conductors in the armature.
- 24.Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type?.
- A.
Compound.
- B.
Shunt (parallel).
- C.
Series.
- 25.A series wound DC motor, the field has.
- A.
Few turns of thin wire.
- B.
Many turns of thin wire.
- C.
Few turns of thick wire. few turns of thick wire. few turns of thick wire.
- 26.Generator brushes are normally made of.
- A.
Steel.
- B.
Carbon.
- C.
Brass.
- 27.What device is used to convert alternating current, which has been induced into the loops of the rotating armature of a DC generator into direct current as it leaves the generator?.
- A.
An inverter.
- B.
A commutator.
- C.
A rectifier.
- 28.Which of the following is not one of the purposes of interpoles in a generator?.
- A.
Overcome armature reaction.
- B.
Reduce arcing at the brushes.
- C.
Reduce field strength.
- 29.How are generators rated?.
- A.
Impedance at rated voltage.
- B.
Amperes at rated voltage.
- C.
Watts at rated voltage.
- 30.Some electric motors have two sets of field winding wound in opposite directions so that the.
- A.
Speed of the motor can be more closely controlled.
- B.
Motor can be operated in either direction.
- C.
Power output of the motor can be more closely controlled.
- 31.What polarity do interlopes take in a DC motor?.
- A.
Either, provided they lay on the MNA.
- B.
The same as the next main pole ahead in the direction of rotation.
- C.
The same as the next main pole behind in the direction of rotation.
- 32.In a generator, armature reaction causes the MNA to move.
- A.
Against the direction of rotation.
- B.
In the direction of rotation.
- C.
To the GNA.
- 33.What is the principal advantage of the series-wound DC motor?.
- A.
Suitable for constant speed use.
- B.
High starting torque.
- C.
Low starting torque.
- 34.Interpole windings fitted to DC series wound generators are.
- A.
In series with the armature
- B.
In series with the field.
- C.
In parallel with the armature.
- 35.Interpole windings carry
- A.
The same current as the field.
- B.
The same current as the armature.
- C.
Induces current in the generator.
- 36.The method most often used in overcoming the effect of armature reaction is through the use of.
- A.
Shaded poles.
- B.
Interpoles.
- C.
Drum-wound armatures in combination with a negatively connected series field.
- 37.If a motor is spinning at 50 cycles per second, how long is 1 cycle of the output?.
- A.
50 seconds.
- B.
0.83 seconds.
- C.
0.02 seconds.
- 38.The windings embedded in the pole faces of a DC generator are.
- A.
Commutating coils.
- B.
Interpoles.
- C.
Compensating windings.
- 39.A circuit has 28 volts applied. The current flowing through a 2 ohms resistance is 1 amp. Then the other resistor is
- A.
26 ohm in series with 2 ohm resistor
- B.
26 ohm in parallel with 2 ohm resistor
- C.
26 ohm in series with 1 ohm resistor
- 40.The mass of an atom is contained mainly in the.
- A.
Proton.
- B.
Neutron.
- C.
Nucleus.
- 41.Which filter is used to pass low frequency but attenuates higher frequency?
- A.
Low pass
- B.
High pass
- C.
Band pass
- 42.When cells are connected in series, voltage-
- A.
Subtractive
- B.
Additive
- C.
Same as source voltage
- 43.Resistance is independent of-
- A.
Temperature
- B.
Mass of conductor
- C.
Material of conductor
- 44.Transformer having no loss-
- A.
Voltage transformer
- B.
Step up
- C.
Ideal
- 45.Reactive Power is
- A.
IV
- B.
IVsinɸ
- C.
IVcosɸ
- 46.The 4th band represents -
- A.
Multiplier
- B.
Tolerance
- C.
Error
- 47.Faraday’s Laws States that
- A.
The magnitude of EMF is indirectly proportional to the magnetic Flux
- B.
The magnitude of EMF is directly proportional to the rate of change of Flux
- C.
The magnitude of EMF is indirectly proportional to the rate of change of Flux
- 48.Solar cell is an example of ______ source
- A.
Chemical
- B.
Thermal
- C.
Light
- 49.The magnet holds some of its magnetism, the property was-
- A.
Reluctance
- B.
Retentively
- C.
Permittivity
- 50.Opposition to magnetic field-
- A.
Reluctance
- B.
Resistance
- C.
Permeability
- 51.Which property associated with magnetism
- A.
Permittivity
- B.
Coercivity
- C.
Both
- 52.A material has low permeability
- A.
Diamagnetic
- B.
Paramagnetic
- C.
Ferromagnetic
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