EASA : Module3 Electrical Fundamentals Question Part-2
EASA : Module3 Electrical fundamentals Question - Answer
In cold weather a battery must be kept
Ans a) fully charged
b) fully discharged
c) does not matter
*
A simple basic induction motor has
Ans a) poor starting torque, good running torque
b) good starting torque, poor running torque
c) poor starting torque, poor running torque
*
If the frequency to a capacitor increases, the current through it
Ans a) is zero
b) increases
c) decreases
*
In a 3-phase delta wound circuit, line current is
a) same as the phase current
b) in phase with the phase current
Ans c) the vectorial sum of all 3 phase currents
*
Conductance of a circuit is 2 milliMhos. What is its resistance?
a) 5 MegaOhms
Ans b) 500 Ohms
c) 5000 Ohms
*
To increase the voltage output of a generator you can
Ans a) increase speed
b) decrease speed
c) It is not speed dependant
*
How would you find the direction of the current flow in an armature located in a magnetic field?
a) Maxwells corkscrew rule
Ans b) Flemings right hand rule
c) Fleming's left hand rule
*
If in a electrical circuit there is a difference between the capacitive reactance and the inductive reactance, what would the power factor of the circuit be?
a) Unity
Ans b) Less than unity
*
What is the SI unit of conductance?
Ans a) Sieman
b) Ohm
c) Ohm-metre
*
What is the SI unit of resistivity?
Ans a) Ohm metre
b) Ohms/metre
c) Ohms
*
Generator voltage is
Ans a) dependant on speed of rotation
b) independent of speed of rotation
c) not dependant on speed of rotation
*
If a negatively charged conductor is placed next to an insulated rod
a) the rod has no charge
b) the rod becomes negatively charged
Ans c) the rod becomes positively charged
*
What is the formula for conductance?
Ans a) 1/R
b) 1 - R
c) R + 1
*
What happens if you reverse the supply to the field and armature of a DC shunt motor?
a) Reverses direction of rotation
Ans b) Continues to rotate in same direction
c) Fails to start
*
The internal resistance of a battery off load compared to on load is
Ans a) same
b) increased
c) decreased
*
What is the rating of a monolithic capacitor with 103 on it
Ans a) 10000pf
b)100000pf
c) 1000pf
*
What is the formula for working out the capacitance of a capacitor if K = dielectric constant, A = area of the plates, d = distance plates apart?
Ans a) c = KA/d
b) c = Kd/A
c) c = d/KA
*
115V RMS 2.5A at 60 degrees what is the power disipated?
a) 79 W
Ans b) 143 W
c) 300 VA
*
If cobalt has a permeability of 4800 it is a
Ans a) ferromagnetic
b) paramagnetic
c) diamagnetic
*
The output from a generator to a commutator is
Ans a) AC
b) DC
c) pulsed DC
*
When light hits a photodiode resistance
a) increases
Ans b) decreases
c) stays the same
*
What type of wave is it when the vertical and horizontal distances are equal?
Ans a) Square
b) Rectangular
c) Sawtooth
*
Cobalt has permeability
Ans a) greater than unity
b) same as unity
c) less than unity
*
In an aircraft brushless alternator the armature is
a) in series with the field
Ans b) star wound
c) delta wound
*
to supply a 24 volt output with a transformer with a 5:1 turns ratio,
the input required is
Ans a) 120V
b) 4.8V
c) 24V
*
In a resonant parallel circuit, current is
a) max
Ans b) min
c) zero
*
Total capacitance of 3 capacitors each 12mF in a parallel circuit
Ans a) 36mF
b) 12mF
c) 6mf
*
Band stop filter
Ans a) attenuates frequencies in a specified narrow band
b) stops frequencies in a narrow band
c) pass all frequencies in that band
*
A combination of 1 megohm and 8 microfarad would give a time constant of
a) 40 seconds
Ans b) 8 seconds
c) 400 ms
*
Power factor is
a) sin theta
Ans b) cos theta
c) tan theta
*
What is the main disadvantage of a starter generator?
Ans a) Will not supply output at low rpm
b) Heavier than like for like
c) Can only be used on piston engines
*
What is the voltage across a fully charged capacitor?
Ans a) Same as circuit voltage
b) Less than circuit voltage
c) More than circuit voltage
*
When would you use an electrolytic capacitor?
a) On a balanced circuit
Ans b) Large output compared to size required
c) Low output compared to size required
*
If the phase voltage of a star wound generator is 115V, what would be the line-to-line voltage?
Ans a) 200V
b) 180V
c) 220V
*
Back-EMF is the greatest when a motor is
Ans a) at operating speed
b) just starting to rotate
c) under heavy load
*
What are the factors affecting the frequency of an ac generator?
a) Number of turns in the armature coil and rpm
Ans b) Number of pole pairs and rpm
c) Number of turns in the armature coil and number of pole pairs
*
Which of the following applications would require a "continuously rated" motor
a) Flap drive actuator
Ans b) Fuel pump motor
c) Cargo door actuator
*
What would you use for the core in a generator current transformer?
Ans a) Air core
b) Laminated core
c) Steel Core
*
Spontaneous magnetisation occurs in a
a) permomagnet
Ans b) ferromagnet
c) diamagnet
*
An aircraft transformer is needed to step up a voltage. What sort would be used
a) Air core
Ans b)Laminated core
c) Solid core
*
A conductor is placed in a magnetised coil. What will happen
a) A force will be created
Ans b) Nothing will happen unless the conductor is moved
c) The conductor will move
*
An atom with less than 4 electrons in its outer shell has
Ans a) low electrical resistance
b) high electrical resistance
c) no electrical resistance
*
In a 4:1 step-up transformer, 120V is applied to the primary, and the load on the secondary is 1600 Ohms. What is the current in the primary?
a) 0.075A
Ans b) 1.2A
c) 3A
*
Two 12V, 40Ah cells in series gives
Ans a) 24V 40Ah
b) 24V 80Ah
c) 12V 40Ah
*
A 2 Megohm resistor can be written
a) M20F
Ans b) 2M0F
c) 20MF
*
If a resistor is too small or misshapen to fit the colour code bands, how else is it's value indicated?
a) Dots
Ans b) Letter code
c) Number code
*
Elements such as phosphorus with 5 electrons in their outer shell, when combined with pure silicon, is a
Ans a) donor
b) acceptor
c) isotopic
*
This is a diagram of a
Ans a) Light Dependant Resistor
b) Logarithmic Differential Resistor
c) Laser Diode Rectifier
*
A centrifugal speed switch is used
Ans a) to cut out the resistor/inductor circuit on an AC motor
b) to cut out the capacitor circuit on an AC motor
c) to cut in the resistor/inductor circuit on an AC motor
*
Disconnecting one of the phases from a 3-phase motor will cause the motor to
a) stop
Ans b) run a 2/3 speed
c) run at the same speed
*
To find the internal resistance of a battery in a circuit of known current
a) use the formula R = V x I
Ans b) find the lost volts of the circuit
What effect does hydrogen have in a battery cell?
Ans a) Polarization
b) Sulphation
c) Nothing
*
Eddy current losses in a transformer are
Ans a) current used in magnetising the core
b) current flow induced into the core
c) hysteresis losses
*
A 3-phase star-delta wound transformer gives
a) 90° phase shift
b) no phase shift
Ans c) 30° phase shift
*
In a parallel circuit containing resistors
Ans a) the voltage is the same in all parts of the circuit
b) the sum of the voltage drops equals applied voltage
c) resistance is determined by value of current flow
*
An induced current in a coil
Ans a) opposes the EMF producing it
b) aids the EMF producing it
c) does not affect the EMF producing it
*
Armature reaction is
a) reactive sparking
b) due to dirty or worn commutator
Ans c) the MMF opposing rotation
*
In a 4:1 step up transformer, what would give a reflected impedance of 1K ohm
a) 1 k ohm
b) 4k ohm
Ans c) 16k ohm
*
Lines of magnetic flux pass from
Ans a) N to S
b) E to W
c) S to N
*
A shunt motor
a) gives constant torque with variations in speed
Ans b) is constant speed
c) has high starting torque
*
The direction of current in a wire rotating in a magnetic field can be determined by
Ans a) Fleming's right hand rule
b) Fleming's left hand rule
c) cork screw rule
*
The diagram shows a 200V long shunt generator. What is the voltage across the series resistor?
a) 30V
Ans b) 6V
c) 10V
*
In a parallel LCR circuit, if the capacitance is increased by 4 times, what happens to the impendence?
a) increases by 4 times
Ans b) decreases by 75%
c) remains the same
*
in a DC shunt motor, if the field resistance is increased what happens to the back EMF?
a) increases
Ans b) decreases
c) remains the same
*
Why is ferrite used in memory circuits?
Ans a) High remanence
b) Low permeability
c) High reluctance
*
What semi-conductor material is used in memory circuits?
Ans a) Ferrite
b) Permeomag
c) Iron
*
The discharge curve of a capacitor is
a) Linear
b) Logarithmic
Ans c) Exponential
*
to generate electricity with a fuel cell, you need a constant supply of
Ans a) Oxygen & Hydrogen
b) Kerosene & Heat
c) Nitrogen & Sunlight
*
Five different value resistors all have the same voltage dropped across them, how are the resistors connected?
a) In Series
Ans b) In Parallel
c) In Series/Parallel
*
The input is 115V and is applied across the 300 turn portion. What is the output?
Ans a) 460V
b) 115V
c) 28V
*
A near perfect 4:1 step up transformer has it's primary connected to 120VAC, if the secondary is connected to a load with 1600 ohms resistance what is the current in the primary
a) 1 amp
b) 0.3 amps
Ans c) 1.2 amps
*
Flux losses in a transformer can be prevented by
a) the use of primary shielding
Ans b) winding the primary on top of the secondary
c) laminating the core
*
A ni-cad battery found to be below normal capacity should
a) be removed and used for ground use only
Ans b) be re-charged with a freshening charge
c) have its electrolyte adjusted
*
In a series LCR circuit at resonance, R = 100 ohms, L and C are each 10 ohms. The total impedance is
Ans a) 100 ohms
b) 30 ohms
c) zero ohms
*
An AC generator has four poles. To produce a frequency of 400Hz it must achieve a speed of
a) 6000 RPM
b) 8000 RPM
Ans c) 12000 RPM
*
If an AC sinewave has an RMS value of 5V its peak value is
a) 14.14 V
b) 6.37 V
Ans c) 7.07 V
*
The Daniel Cell electrodes are
Ans a) copper and zinc
b) carbon and zinc
c) zinc and manganese dioxide
*
An inductor of resistance 5 k ohms and inductance 2mH is connected to a DC circuit. The time constant is
Ans a) 400 ns
b) 10 seconds
c) 40 ms
*
The unit of flux is the
Ans a) Weber
b) Ampere turns
c) Ampere turns / metre
*
The flux density of a magnetic field is 1.5T. The length of the conductor in the field is 2 m and the speed of the conductor is 10 m/s. The EMF induced is
a) 0.3 V
Ans b) 30 V
c) 7.5 V
*
A DC generator armature has 6 poles and is lap wound. The number of brushes required are
Ans a) 6
b) 2
c) 3
*
Reactive sparking is reduced by
Ans a) interpoles
b) compensating windings
c) auxiliary windings
*
The back EMF in a DC motor is
a) equal to the applied EMF
Ans b) less than the applied EMF
c) greater than the applied EMF
*
The flux density of a magnetic field is 1.5T. The length of the conductor in the field is 2 m and the current flowing through the conductor is 5 amps. The force on the conductor is
Ans a) 15 Newtons
b) 0.6 Newtons
c) 3.75 Newtons
*
A DC shunt motor has 28 volts applied. The current taken from the armature of 2 ohms resistance is 1 amp. The BEMF is
a) 30 V
b) 27 V
Ans c) 26 V
*
In a motor, armature reaction causes the MNA to move
a) in the direction of rotation
Ans b) against the direction of rotation
c) to the GNA
*
A circuit with good selectivity will have
a) a large bandwidth
Ans b) a narrow bandwidth
c) a low L/C ratio
*
Apparent power in an AC circuit is found by
Ans a) V x I
b) V x I x cosØ
c) V x I x sinØ
*
A 300 ohm resistor would have a colour code of
a) orange, orange, brown
b) orange, brown, black
Ans c) orange, black brown
*
In a synchronous motor, when the motor is running the slip is
a) 100%
b) 5%
Ans c) 0%
*
In a two-phase induction motor there are
a) 2 poles
b) 3 poles
Ans c) 4 poles
*
The diagram shown is a
a) short shunt compound wound machine
Ans b) long shunt compound wound machine
c) shunt wound machine
*
A transformer has 500 turns on the primary and 100 turns on the secondary. When connected to a 100 V supply, the output is
a) 500 V
Ans b) 20 V
c) 25 V
*
In the previous question, the secondary is connected to a 10 ohm load. The primary current is
a) 10 amps
Ans b) 0.4 amps
c) 2 amps
*
Magneto motive force can be found by
a) N/I
Ans b) I x N
c) Blv
*
Permeability of a material can be found by
Ans a) flux density / MMF
b) MMF x flux density
c) MMF / flux density
*
A filter with a small bandwidth has
Ans a) a high value of Q
b) a low value of Q
c) a Q of zero
*
A transformer has 1200 turns primary and 4800 turns secondary. What value of load resistance would be required to give a reflected impedance of 1000 ohms
a) 1 kohm
b) 4 kohm
Ans c) 16 kohm
*
An autotransformer windings are
a) on separate formers
Ans b) connected
c) wired in parallel
*
What voltage can the neutral line carry in a star transformer?
a) Combined line voltages
Ans b) Zero voltage
c) Phase voltage
*
In a generator system, a stabilizing winding is used
a) in series with the field to prevent oscillations
Ans b) to prevent voltage overshoot
c) to control output current
*
When magnetizing a piece of material, magnetic strength will rise
a) linearly with coercive force
b) linearly with magnetic force
Ans c) non-linearly with magnetic force
*
The stator of a permanent magnet rotor AC generator
a) is wound in series with the field
b) is usually delta wound
Ans c) is usually star wound
*
In a resistive/inductive motor
Ans a) the resistor circuit must be disconnected after starting
b) is less efficient than a capacitor start motor
c) can only be used for light loads
*
When a conductor is cut by magnetic lines of force an EMF is induced. This is
a) Lenz's Law
Ans b) Faraday's Law
c) Kirchoff's Law
*
A 47K resistor has the following color code
Ans a) Yellow, Violet, Orange
b) Orange, Violet, Red
c) Red, Orange, Yellow
*
A material with a narrow hysterisis loop
a) has a high retentivity
Ans b) has a low retentivity
c) cannot be magnetised
*
The power output of a similar sized 3 phase compared to a single phase generator is
a) less
b) same
Ans c) more
*
What part of a DC motor would you find the poles?
a) brushes
Ans b) stator
c) rotor
*
in a high Q parallel resonant circuit, what happens to impedance if capacitance is increased by a factor of 4?
Ans a) It reduces by 75%
b) It remains the same
c) It increases by factor of 4
*
In a thermocouple where is voltage measured?
a) At the hot junction
Ans b) At the cold junction
c) At both junctions
*
Mercury cells are covered with a metal cover
a) as a protective cover
Ans b) as a positive terminal
c) as a negative terminal
*
When switching off the supply, the back emf in a collapsing field in an inductor
a) never exceeds forward emf
Ans b) can be multiple times bigger than forward emf
c) is equal to forward emf
*
If the energy supplied to a circuit for 4hrs 15 mins at 800 j/sec what would be the energy consumed?
Ans a) 3.4 KW Hrs
b) 3400 KW Hrs
c) 340 KW Hrs
*
A parallel circuit at resonance has its impedance at a
Ans a) maximum
b) minimum
c) zero
*
A parallel circuit with any number of 2 terminal connections
a) has the same current throughout
Ans b) the individual voltage drops is equal to the emf
c) the resistance is dependent on current
*
In this circuit, Rx is equal to
Ans a) R3 x R2 ÷ R4
b) R3 x R4 ÷ R2
c) R2 x R4 ÷ R3
*
A transformer to supply a 24V load with a 5:1 turn's ratio will have what primary supply?
a) 120 VDC
b) 48 VAC
Ans c) 120 VAC
*
A material exposed to heat will
Ans a) be harder to magnetise
b) be easier to magnetise
c) have no effect on magnetism
*
A 20 Pico farad capacitor with a 1MW resistor takes how long to charge?
a) 20 milli seconds
Ans b) 0.1 second
c) 10 seconds
*
A transformer has 2000V, 500 turns on the primary and 50 turns on the secondary. What would be the line voltage if the transformer were Delta/Star connected?
a) 200V
Ans b) 346V
c) 450V
*
The main advantage of a starter-generator over conventional units is
a) for the same power output there is a weight reduction and the starter drive remains engaged
Ans b) for the same power output there is a weight reduction and the drive is constantly engaged
c) it can produce a greater power output
*
The speed of a single phase induction motor is dependant on
a) the strength of the field
Ans b) the number of pairs of poles
c) the strength of the armature current
*
An A.C. shunt wound motor sometimes uses a volts dropping resistor. The resistor would be
Ans a) in series with the supply
b) in series with the field
c) in series with the armature
*
The time to fully charge a 1 micro farad capacitor in series with a 100K ohm resistor is
Ans a) 100 ms
b) 10 ms
c)1 ms
*
A sine wave has a periodic time of 0.5 milliseconds, what is its frequency?
a) 200 Hz
Ans b) 2Khz
c) 20Khz
*
In a voltage equalizing circuit the generators are regulated so
a) the lower output is increased to that of the higher
b) the higher output is decreased to that of the lower
Ans c) the lower is increased and the higher is decreased until they are equal
*
The capacity of a battery is measured in
a) volts
b) cubic centimeters
Ans c) ampere-hours
*
Phase angle is
Ans a) the difference in degrees of rotation between 2 alternating voltages or currents or a voltage and a current
b) the difference in degrees between the positive and negative parts of an ac sine wave
c) the cosine of the peak value of an ac voltage
*
The impedance of an ac circuit is measured in
a) kilovolt-amperes
b) amperes
Ans c) ohms
*
The formula for impedance in a series circuit is
Ans a)
b)
c)
*
Motor slip is
Ans a) the percentage of difference in speeds between the stator and rotor fields
b) a shifting of the MNA of the motor
c) a symptom of a weak field
*
The principal characteristic of a synchronous motor is
Ans a) it rotates at a speed that is synchronised with the applied ac current
b) it must have a synchronised 3 phase supply to operate
c) it rotates at a speed that is synchronised with the applied dc current
*
There are more negative than positive plates in a lead acid battery because
Ans a) the positive plates are prone to warping if the chemical action is taking place only on one side
b) it reduces the internal resistance of the cell
c) it is necessary for chemical action to take place
*
Commutator ripple can be reduced by
Ans a) the use of a ripple filter
b) increasing generator frequency
c) a resistor in series with the armature
*
In this circuit applied voltage is
Ans a) Vt= IXC
b) Vt = IXL
c) Vt = I/R
*
What is the internal resistance of a Leclanche cell?
a) 6 ohms - 10 ohms
Ans b) 0.02 ohms - 4 ohms
c) 20 ohms - 30 ohms
*
In a DC motor the interpoles are part of the
Ans a) field
b) rotor assembly
c) stator assembly
*
The line voltage in a wye wound transformer is
a) root 3 / phase voltage
b) the same as phase voltage
Ans c) root 3 x phase voltage
*
The valence electron is
Ans a) the electron in outer shell of atom
b) the electron in inner shell of atom
c) a positive electron
*
An aircraft battery on charge from the aircraft generators causes
a) internal resistance of the battery to decrease in sympathy with the decreasing charging current
Ans b)battery voltage to increases to nominal voltage and the charge current decreases
c) battery voltage to decrease to zero until it is fully charged
*
What happens to the current in a series resistive resonant circuit?
Ans a) It is maximum
b) It is minimum
c) It is zero
*
An atom with a deficiency in electrons has
a) high resistance
Ans b) low resistance
c) high impendence
*
The unknown current in the network below is
a) 22A
Ans b) 3A
c) 47A
*
The Watt can be expressed as
Ans a) Joules per second
b) Joules x seconds
c) Seconds per Joule
*
A single phase circuit has an input voltage of 100V. The current is 10A and the circuit has a power factor of 0.5. The true power is
a) 1000W
b) 50W
Ans c) 500W
*
Power in a DC circuit is found by
a) multiplying current by resistance
b) multiplying the voltage by itself and dividing by the current
Ans c) multiplying the resistance by the current squared
*
The total capacitance of the circuit shown is
Ans a) 4µF
b) 36µF
c) 3µF
*
When a capacitor is charged from a DC supply, the voltage / time curve is
a) logarithmic
Ans b) exponential
c) linear
*
An electrolytic capacitor is used because it has a
a) large physical size for a large capacity
Ans b) small physical size for a large capacity
c) small physical size for low leakage current
*
An electrolytic capacitor would be used in circuits supplying
a) heavy loads
b) light loads
Ans c) heavy / light loads
*
The symbol for flux density is
a) H
Ans b) B
c) MMF
*
The hysteresis loop for a magnetic material is on a graph with
a) total flux against flux density
b) current against flux density
Ans c) flux density against magnetising force
*
To determine the direction of the magnetic field around a conductor you would use
Ans a) the corkscrew rule
b) Fleming's left hand rule
c) Fleming's right hand rule
*
A material with a narrow hysteresis loop
a) will have high retentivity
Ans b) will have low retentivity
c) cannot be magnetised
*
If a bar magnet is cut in half
a) the magnet is destroyed
Ans b) two bar magnets are formed
c) one bar magnet and one non-magnet is formed
*
The diagram shows a current carrying conductor in a magnetic field. The conductor will move
a) upwards
Ans b) downwards
c) sideways
*
The electromagnetic force between two charged bodies is
a) proportional to the distance between them
b) inversely proportional to the distance between them
Ans c) inversely proportional to the square of the distance between them
*
Copper is a
a) paramagnetic materials
b) ferromagnetic material
Ans c) diamagnetic material
*
Switching on or off the current in one coil produces an emf in another coil adjacent to it. The two coils are said to have
a) self inductance
Ans b) mutual inductance
c) auto inductance
*
The time constant in an inductive circuit is the time required for the current to reach
Ans a) 63.2% of maximum value
b) 63.7% of maximum value
c) 70.7% of maximum value
*
The MMF of a coil fed with 2 amps and having 10 turns is
a) 5 ampere turns
Ans b) 20 ampere turns
c) 20 amperes / turn
*
An AC inductive circuit has an inductance 0f 10 mH and a frequency input of 1000Hz. The opposition to current flow is approximately
a) 63,000 ohms
b) 630 ohms
Ans c) 63 ohms
*
A sine wave of RMS value 7.07 volts has a peak to peak value of
a) 10.0 volts
b) 0.707 volts
Ans c) 20.0 volts
*
The true power in an AC circuit is given by
a) voltmeter reading x PF
b) volts x amps
Ans c) volts x amps x PF
*
The average value of 100 volts peak AC is
a) 70.7 volts
b) 141.4 volts
Ans c) 63.7 volts
*
The RMS value of 200 volts peak to peak is
a) 141.4 volts
Ans b) 70.7 volts
c) 127.4 volts
*
The impedance of a series tuned circuit at resonance is
a) zero
b) maximum
Ans c) minimum
*
The copper loss on a single phase transformer is 25 Watts on full load. What will it be on half load?
a) 5 Watts
b) 12.5 Watts
Ans c) 6.25 Watts
*
Rotating coil B through 90o will
a) increase the EMF induced into B
Ans b) decrease the EMF induced into B
c) increase the EMF induced into A
*
A transformer is designed to operate at 60 Hz. It is connected across a 50 Hz supply. The primary windings would
Ans a) draw more current
b) draw less current
c) draw the same current
*
A current transformer, when disconnected from a circuit must be
a) left open circuit
Ans b) short circuited
c) have a resistor connected across the terminals
*
What is the reflected impedance in the primary?
a) 20 ohms
Ans b) 500 ohms
c) 50 ohms
*
A transformer rated at a frequency of 200 Hz
a) may be used at any other frequency
Ans b) may only be used at the rated frequency or above
c) may only be used at the rated frequency or below
*
The dots are called, and indicate
a) quadrature dots, points are 90o out of phase
Ans b) phasing dots, point that have the same polarity at the same moment in time
c) phasing dots, point that have the opposite polarity at the same moment in time
*
The power factor of an AC circuit is the
a) sine of the phase angle
Ans b) cosine of the phase angle
c) tangent of the phase angle
*
The Form Factor of an AC waveform can be found by
Ans a) RMS value divided by the average value
b) average value divided by the RMS value
c) average value times the RMS value
*
A differentiator has a time constant which is
a) long
Ans b) short
c) equal to the input pulse
*
If the frequency is increased in an AC circuit of pure resistance, the effect is
a) increased resistance
b) decreased resistance
Ans c) nothing
*
A wire is rotated through a magnetic field. To give DC it must be connected to
Ans a) a commutator
b) slip rings
c) a rectifier
*
In an inductive resistive circuit, 1 amp flows from a supply of 100V dissipating 50 Watts of power. The phase angle is
Ans a) 60o
b) 90o
c) 45o
*
A transformer is built with a material having a
Ans a) narrow hysteresis loop
b) wide hysteresis loop
c) high coercive force
*
An alternator delivers 500V RMS at 1 ampere. The power factor is 0.8. The true power is
a) 100VA
Ans b) 400W
c) 500W
*
In a circuit which possesses mutual inductance, current is increased to the primary
Ans a) the induced EMF in the secondary produces a current in the secondary circuit which opposes the increase in flux due to the increase of current in the primary
b) the induced EMF in the secondary produces a current in the secondary circuit which assists the increase in flux due to the increase of current in the primary
c) the induced EMF in the secondary produces a current in the secondary circuit whose flux has no effect on the flux in the primary
*
A component that produces an output voltage due to incident light is called a
a) liquid crystal
b) light emitting diode
Ans c) solar cell
*
If the supply to a DC shunt motor was reversed
a) it would rotate in the opposite direction
b) it would fail to run
Ans c) it would rotate in the same direction
*
Slip on a synchronous motor on start is
a) 0%
b) 50%
Ans c) 100%
*
A shaded pole motor has shaded poles to
a) increase efficiency
Ans b) create a rotating field
c) reduce interference
*
A series motor draws a high current on start, and then the current reduces. This is due to
a) the resistance of the field and the armature in series
Ans b) the back EMF
c) the resistance of the field and armature in parallel
*
on a brushless AC generator, the main rotating field is fed with
a) AC
Ans b) DC via diodes on the rotor
c) AC from the rotating field exciter
*
Single phase components in a three phase system may be connected between
a) phase A and B only
b) phase and neutral only
Ans c) any phase and neutral OR between any two phases
*
Interpoles in a DC generator are connected
a) in parallel with the armature
Ans b) in series with the armature
c) in series with the field
*
In a DC generator, the effect of armature reaction may be reduced by moving the brush gear
a) from MNA to GNA
Ans b) in the direction of armature rotation towards the MNA
c) against the direction of armature rotation towards the MNA
*
The windings embedded in the pole faces of a DC generator are
a) interpoles
b) commutating coils
Ans c) compensating windings
*
A 6 pole wave-wound generator has
Ans a) 2 brushes
b) 6 brushes
c) 3 brushes
*
In a 2 phase induction motor the control winding is fed with
a) variable phase AC supply
b) fixed AC supply
Ans c) variable amplitude supply only
*
A 3 phase induction motor can be reversed by
a) isolating one phase
b) reversing the rotor connections
Ans c) changing over any two phases
*
The speed of an AC motor can be affected by the
a) field current
Ans b) pairs of poles
c) armature current
*
A generator rated at 30 KVA and power factor 0.8 has a maximum continuous power output of
a) 30 kW
Ans b) 24 kW
c) 37.5 kW
*
An AC motor which rotates at the same speed as the supply frequency is called
a) a universal motor
b) an induction motor
Ans c) a synchronous motor
*
In the circuit shown, impedance will be
a) 9 ohms
Ans b) 5 ohms
c) 7 ohms
*
In the circuit shown, if the frequency is increased from zero to resonant frequency, the circuit current would
Ans a) increase
b) decrease
c) stay the same
*
The true power developed in this circuit is
Ans a) 12W
b) 50W
c) 20W
*
The filter shown is a
a) band stop filter
Ans b) low pass filter
c) high pass filter
*
An example of a paramagnetic material is
Ans a) iron
b) silver
c) glass
*
In a balanced Wheatstone bridge, across the centre of the bridge there is
Ans a) no current flow
b) no voltage present at either end
c) current and voltage at maximum
*
A 24V battery has an internal resistance of 1 ohm. When connected to a load, 12 amps flows. The value of the load is
a) 12 ohms
Ans b) 1 ohm
c) 1/2 ohm
*
The property of a material to accept lines of flux is called
Ans a) permeability
b) reluctance
c) retentivity
*
Armature reaction in a DC generator causes
Ans a) MNA to move in the direction of rotation
b) MNA to move in the opposite direction of rotation
c) GNA to move in the direction of rotation
*
In a DC motor, B-EMF rises if the motor
Ans a) speed rises
b) speed falls
c) load rises
*
Vibration in a magnet causes
a) flux to increase
Ans b) flux to decrease
c) flux to stay the same
*
A high pass filter has
Ans a) high impedance to low frequency, low impedance to high frequency
b) high impedance to high frequency, low impedance to low frequency
c) high impedance to both high and low frequency
*
What sort of wave would be used in a CR oscillascope to control sweep?
Ans a) Sawtooth
b) Square
c) Sine wave
*
If there was a mainly inductive load on an AC generator, the voltage with respect to the current would
Ans a) lead
b) lag
c) be in phase
*
on a brushless AC generator, the permanent magnet generator output is
a) DC
Ans b) AC
c) pulsed
*
The output from a rotating armature AC generator would be taken from
Ans a) the rotor
b) the stator
c) either the rotor or the stator
*
A frequency wild AC generator system has
a) variable voltage and frequency
Ans b) variable frequency only
c) variable voltage only
*
Current in an inductive circuit will
a) lead voltage
Ans b) lag voltage
c) be at unity
*
Power factor of a generator is
a) sin ø
Ans b) cos ø
c) tan ø
*
In a an AC motor, the rotation of the MNA
a) is the same as the rotation of the armature
Ans b) is opposite to the rotation of the armature
c) is slightly less speed than the rotation of the armature
*
in a wave wound generator with 4 poles, what would be the minimum number of brushes?
a) 4
Ans b) 2
c) 8
*
A capacitor rating is
Ans a) the maximum continuous voltage it can take
b) the voltage it will rupture at
c) the voltage it will charge to
*
In conventional flow, the left hand rule applies to
a) generators
Ans b) motors
c) batteries
*
Copper losses in a transformer are caused by
a) circulating currents through the transformer
Ans b) the resistance in the windings
c) wasting of the copper wires due to friction
*
In AC generators, 0.637 is
a) RMS
Ans b) average value
c) form factor
*
In a 3 phase generator, what angle are the phases to each other?
a) 180o
Ans b) 120o
c) 0o
*
In a 2 phase generator, what angle are the phases to each other?
Ans a) 90o
b) 180o
c) 0o
*
Delta wound line current is
a) equal to phase current
Ans b) root 3 x phase current
c) less than the phase current
*
The multiplier color coding on a capacitor is in
a) farads
b) microfarads
Ans c) picofarads
*
Form Factor for a sine wave AC output is
a) 0.707
b) 1.414
Ans c) 1.1
*
In a simple voltaic cell the collection of ions on the cathode causes
a) hydration
Ans b) sulphation
c) polarisation
*
The electrolyte in a nicad battery would rise if the battery was
a) discharging
Ans b) charging
c) remaining at constant voltage
*
When a conductor is cut by magnetic lines of force an EMF is induced. This is
a) Lenz's Law
Ans b) Faraday's Law
c) Kerchoof's Law
*
Two 2 volt 10AH cells are connected in series, the output voltage and the capacity would be
a) 2 volt, 20 AH
Ans b) 4 volt 10 AH
c) 4 volt 20 AH
*
The electrolyte in a nicad battery is
a) cadmium hydroxide
b) nickel hydroxide
Ans c) potassium hydroxide
*
Referring to the drawing below, if the volts dropped across the 20 ohm resistor is 10 volts, the resistance of R1 is
Ans a) 20 ohms
b) 16 ohms
c) 2 ohms
*
The atomic number of an atom is determined by the number of
Ans a) protons
b) electrons
c) neutrons
*
In a Leclanche cell the plates are made of
a) mercury and lithium
b) nickel and cadmium
Ans c) zinc and carbon
*
In a simple voltaic cell, polarization reduces output voltage because of the
a) transfer of material between the anode and the cathode
Ans b) build up of hydrogen on the anode
c) build up of hydrogen on the cathode
*
When the temperature of the electrolyte in a battery increases, the SG
a) goes up
Ans b) goes down
c) remains the same
*
A 47 kilohm resistor has the following color code
Ans a) Yellow, Violet, Orange
b) Orange, Violet, Red
c) Red, Orange, Yellow
*
If the temperature of a pure metal is reduced to absolute zero, its resistance will be
a) infinity
Ans b) practically zero
c) unaffected
*
The bridge circuit shown will be balanced when the value of the unknown resistor R is
a) 18 ohms
b) 14 ohms
Ans c) 2 ohms
*
The current in the circuit below is
a) 5 A
b) 0.2 A
Ans c) 5 mA
*
In the previous question, the power developed across the 10 k ohm resistor is
Ans a) 250 mW
b) 250 W
c) 50 mW
*
What is represented by this diagram?
Ans a) Potentiometer
b) Rheostat
c) Thermister
*
In the following circuit, the input at P is 4 amps and at Q is 5 amps. What is the voltage across the 6 ohm resistor?
Ans a) 54V
b) 1.5V
c) 6V
*
The dielectric constant of a capacitor is a measurement of
Ans a) the electrostatic energy storing capacity of the capacitor dielectric
b) the electrical resistance of the capacitor dielectric
c) the electrical repulsion of electrons within the dielectric material
*
To reverse the direction of rotation on a DC shunt motor, you must change the direction of the current through
Ans a) the field windings or the armature windings
b) the armature windings only
c) the field windings and the armature windings
*
If the field current to a shunt wound DC motor is decreased when operating at a constant load, the motor speed will
a) reduce
Ans b) increase
c) not change
*
An electric current is
a) a surplus of free electron
b) an excitement of electrons in a metal
Ans c) an ordered flow of electrons
*
An atom contains
a) molecules
b) hydrogen
Ans c) electrons
*
What causes a transformer to be noisy?
a) High coil resistance
Ans b) An air gap in the core
c) High core losses
*
Carbon has a
Ans a) negative temperature coefficient
b) positive temperature coefficient
c) temperature coefficient of zero
*
The peak factor for a sine wave is
a) 0.707
Ans b) 1.414
c) 1.11
*
If a motor is spinning at 50 cycles per second, how long is 1 cycle?
Ans a) 0.02 seconds
b) 50 seconds
c) 0.83 seconds
*
An integrated step input at unequal time base produces
a) a square wave
b) a sine wave
Ans c) a saw tooth wave
*
A capacitor in series and inductor in parallel make what kind of filter?
a) Band pass
Ans b) High pass
c) Low pass
*
If a load in series has a current passing through it, the magnetic field can be worked out by using
Ans a) the corkscrew rule
b) left hand rule
c) right hand rule
*
If the current flowing into a junction is 5A, 3A, 4A in and 10A out. What is the 5th wire carrying?
a) 2A in
Ans b) 2A out
c) 5A out
*
If an insulated conductor is placed near to a negatively charged rod, the nearest end of the conductor becomes
a) negatively charged
Ans b) positively charged
c) No change will occur
*
If 2 resistors, one red, yellow, black, gold and the other violet, blue, black, silver were replaced by a single resistor. Ignoring tolerance, what would the color coding be?
Ans a) Brown, black, brown
b) Brown, black, black
c) Black, brown, black
*
Germanium and silicon have how many electrons in their outer shell
Ans a) 4
b) 2
c) 6
*
If a free electron is given to another atom, that atom is a
a) positive ion
Ans b) negative ion
c) valency atom
*
If a nicad battery is not to be used immediately it should be stored
a) fully charged
Ans b) fully dissipated
c) dry
*
A light / heat sensitive cell is a
Ans a) transducer
b) diode
c) transistor
*
In a mercury cell the steel casing is
Ans a) the positive terminal
b) the negative terminal
c) neither
*
To improve the life of a dry cell you would
Ans a) use more zinc
b) use more electrolyte paste
c) us a a pure carbon positive rod
*
What is the voltage at A?
Ans a) 26V
b) 28V
c) 2V
*
The unit for power is equal to
a) N/m
Ans b) Joules per second
c) Volts/Amps
*
The source voltage in the circuit below is
a) 50V
Ans b) 200V
c) 150V
*
The 5th colored band on a resistor represents the
a) tolerance
b) multiplier
Ans c) reliability or temperature coefficient
*
Three 12 microfarad capacitors in parallel. The overall circuit capacitance is
a) 4 microfarads
b) 1 microfarads
Ans c) 36 microfarads
*
Flux density will
a) increase linearly with coercive force
Ans b) increase linearly with magnetic flux
c) decrease linearly with magnetic flux
*
A transformer with a 5:1 ratio has a 24V output. What is the input
a) 120 V DC
b) 4.8 V AC
Ans c) 120 V AC
*
A generator supplies 25 A, 4 V and 50 W. What is the apparent power and the power factor?
a) 100 VA and 2
b) 400 VA and 0.5
Ans c) 100 VA and 0.5
*
In a power circuit, the purpose of an inductor is
Ans a) to dampen power surges
b) to dampen current surges
c) to dampen voltage surges
*
When a number of ferrite pieces are grouped together, they
a) are semi-permanent magnets when DC is passed through them
Ans b) can be used to store binary code
c) electromagnets
*
Ampere turns is calculated by the number of turns
Ans a) multiplied by current
b) divided by current
c) multiplied by magnetic flux
*
A conventional aircraft generator will be
a) series wound
b) delta wound
Ans c) star wound
*
Storage of magnets should be
a) in pairs end to end
b) in a non magnetic pox
Ans c) in pairs with keeper plates
*
A circuit has 1 megohm and 8 microfarads. What is the time constant?
a) 1 second
Ans b) 8 seconds
c) 40 seconds
*
The sum of the instantaneous E.M.F.'s in a three phase system is
a) equal to the line voltage
b) three times the phase voltage
Ans c) zero
*
A capacitor is a barrier to
a) both
b) A.C
Ans c) D.C
*
One revolution of a three phase generator will produce
a) 3 cycles
b) 2 cycles
Ans c) 1 cycle
*
If the North pole of a magnet is brought nearer to the North pole of another magnet
a) attraction between them will be increased
Ans b) repulsion between them will be increased
c) repulsion between them will be reduced
*
A 200 volt motor is taking 10 amperes armature current, the armature resistance is 0.1 ohm. The B.EMF under these conditions will be
a) 201 volts
Ans b) 199 volts
c) 1 volt
*
What is the effect of inserting an iron core into a current carrying coil?
Ans a) The flux density of the original magnetic field produced by the coil is increased
b) The flux density of the original magnetic field remains constant
c) The core tends to move from a stronger to a weaker part of the field
*
What is the total capacitance of a parallel circuit containing three capacitors with capacitance of 0.25microfarad, 0.03microfarad, and 0.12microfarad, respectively?
a) 0.04 µF
b) 0.04 pF
Ans c) 0.4 µF
*
At resonant frequency the phase difference between the voltage and current of an AC supply feeding an inductive and capacitive network is
Ans a) 0 degrees
b) 180 degrees
c) 90 degrees
*
The frequency of a power wave in an AC resistance circuit is
a) the same as the frequency for voltage and current
b) half the frequency for voltage and current
Ans c) twice the frequency for voltage and current
*
The reading on the ammeter in the circuit shown is
a) 3A
Ans b) 6A
c) 12A
*
The 'A' phase of a three phase power system is colour coded
a) blue
b) yellow
Ans c) red
*
The total resistance of the circuit shown is
a) 12 Ohms
Ans b) 3 Ohms
c) 7.5 Ohms
*
What is a method used for restoring generator field residual magnetism?
Ans a) Flash the fields
b) Reseat the brushes
c) Energize the armature
*
A 1µF capacitor is equivalent to
Ans a) 0.000,001 Farads
b) 1,000,000 Farads
c) 0.001 Farads
*
The opposition offered by a coil to the flow of alternating current is called (disregard resistance)
a) impedance
b) reluctance
Ans c) inductive reactance
*
A high surge of current is required when a DC electric motor is first started. As the speed of the motor increase
a) the applied emf increases proportionally
b) the counter emf decreases proportionally
Ans c) the counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature
*
The tolerance of the AC generator frequency is
a) 40 Hz
Ans b) 10 Hz
c) 20 Hz
*
The various parts of an aircraft airframe are maintained at the same potential by
a) the supply bus-bars
b) static discharge wicks
Ans c) bonding
*
When two capacitors are connected in series
a) the charge stored on each is directly proportional to its capacitance
Ans b) the charge stored on each is the same
c) the charge stored on each is inversely proportional to the voltage across it
*
Aircraft generators are cooled by
a) oil cooling radiators around the main body
b) fuel cooling radiators
Ans c) ram air
*
The voltage of an AC generator
a) rises to max in one direction, falls to zero and rises in the same direction
Ans b) rises to max in one direction then falls to zero then rises to max in the opposite direction
c) rises to max in one direction and remains
*
The charge on a capacitor is expressed as
a) the ratio Q/V
b) the product Q x V
Ans c) the product C x V
*
A shunt is used with
Ans a) an ammeter
b) an ohmmeter
c) a voltmeter
*
The resistance of the current return path through the aircraft is always considered negligible, provided the
a) generator is properly grounded
b) voltage drop across the circuit is checked
Ans c) structure is adequately bonded
*
An ammeter is connected into a circuit in
a) parallel
b) shunt
Ans c) series
*
When handling a high voltage capacitor in an electrical circuit, be sure it
a) has a full charge before removing it from the circuit
Ans b) is fully discharged before removing it from the circuit
c) has at least a residual charge before removing it from the circuit
*
When a circuit with a series inductance and capacitance is at resonant frequency
a) the current in the circuit decreases
Ans b) the impedance of the circuit is such that the voltage is in phase with the current
c) the impedance of the circuit is such that the voltage leads the current by exactly 90 degrees
*
in an AC circuit, the effective voltage is
a) equal to the maximum instantaneous voltage
b) greater than the maximum instantaneous voltage
Ans c) less than the maximum instantaneous voltage
*
On a combined DC starter - generator system
Ans a) the voltage regulator is connected to the shunt field after the start cycle is completed
b) the series coil is open circuit during the engine start sequence
c) the voltage regulator controls the start sequence during engine starting
*
A pure capacitor, inductor and resistor are connected in series and the voltage drops across each are 10V and the total current flowing in the circuit is 1A. How much true power is the circuit consuming?
a) 30VA
b) 30W
Ans c) 10W
*
If a capacitor 1µF and an inductor 10mH are connected in parallel what is their approximate resonant frequency?
a) 62Hz
b) 3.2MHz
Ans c) 1.6kHz
*
Which wave form is stepped positive and negative with unequal length sides?
Ans a) Trapezoidal wave
b) Rectangular wave
c) Saw tooth wave
*
The value of an AC sine wave that will give an equivalent heating effect in a DC resistor is the
a) average value
Ans b) RMS value
c) peak value
*
Where is the magnetic dip least?
a) Poles
Ans b) Equator
c) Isoclinals
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