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A condenser in parallel with breaker points will ? [ Deepen EASA ]

Question 27-1 : Intensify current in secondary winding assist in collapse of secondary winding permit arcing across points assist in negative feedback to secondary coil

This question is about the ignition on a piston engine and the use of a magneto .the components of a typical magneto consist of . a permanent magnet . a primary and a secondary windings on a core . a way of making the magnet or the core move by rotating either one . contact breaker points . a condenser capacitor . a distributor .inside the primary circuit is a set of conctact points that make the flux reversals more abrupt when they open and close at critical moments .the condenser capacitor is mainly there to absorb the sparks and reduce arcing to stop the points getting pitted and worn it is connected across the contact points so it is shorted out when they close but the instant they open it absorbs the current from the collapsing current in the primary coil i e it is charged so the points open cleanly with very few sparks this is know as a spark quench the current from the capacitor when it discharges also hastens the collapse of the primary field by opposing it to increase the induced voltage .the more sudden the breaking of the primary circuit is the more current will be induced in the secondary coil exemple 127 Intensify current in secondary winding.Intensify current in secondary winding.

A unit that converts electrical dc into ac is ?

Question 27-2 : An inverter an ac generator a transformer rectifier unit a thermistor

Dc to ac inverter .ac to dc rectifier exemple 131 An inverter.An inverter.

On board electrical systems are protected against faults of the following type ?

Question 27-3 : 1 2 3 4 5 1 2 4 6 1 3 5 6 2 3 4 5 6

The on board electrical systems are protected for all of these scenarios except for vibration of the generator exemple 135 1, 2, 3, 4, 5.1, 2, 3, 4, 5.

The purpose of a battery control unit is generally to isolate the battery .1 ?

Question 27-4 : 1 2 and 3 1 1 and 2 1 2 3 and 4

exemple 139 1, 2 and 3.1, 2 and 3.

The resistors r1 and r2 are connected in parallel the value of the equivalent ?

Question 27-5 : 1/req = 1/r1 + 1/r2 req = r1 x r2 1/req = 1/ r1 + r2 req = r1 + r2

exemple 143 1/req = 1/r1 + 1/r21/req = 1/r1 + 1/r2

The function of the generator breaker is to close when the voltage of the ?

Question 27-6 : Generator is greater than battery voltage and to open when the opposite is true alternator is greater than the battery voltage and to open when the opposite is true battery is greater than the generator voltage and to open when the opposite is true battery is greater than the alternator voltage and to open when the opposite is true

The generator breaker is controlled by sensors that detect over/under speed over/under frequency reverse or over current plus the control for bringing the generator on or offline .the function of the generator breaker is to close when the voltage of the generator is greater than battery voltage and to open when the opposite is true exemple 147 Generator is greater than battery voltage and to open when the opposite is true.Generator is greater than battery voltage and to open when the opposite is true.

The input and output of a static inverter are respectively ?

Question 27-7 : Dc and ac ac and ac dc and dc ac and dc

exemple 151 Dc and ac.Dc and ac.

Alternating current can be derived from direct current by ?

Question 27-8 : An inverter a series wound motor an alternating current motor the use of relays

exemple 155 An inverter.An inverter.

The rating of electrical fuses is expressed in ?

Question 27-9 : Amperes volts watts ohms

exemple 159 Amperes.Amperes.

A 'zener' diode is used for ?

Question 27-10 : Voltage stabilisation rectification reverse current protection digital displays

A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode but will also permit it to flow in the reverse direction when the voltage is above a certain value but keeps it constant .the zener diode is used for voltage stabilisation exemple 163 Voltage stabilisation.Voltage stabilisation.

The type of gate which requires all conditions with logic 1 for engagement is ?

Question 27-11 : And or nand nor

A logic gate is an elementary building block of a digital circuit most logic gates have two inputs and one output at any given moment every terminal is in one of the two binary conditions low 0 or high 1 represented by different voltage levels the logic state of a terminal can and generally does change often as the circuit processes data .there are seven basic logic gates and or xor not nand nor and xnor .the and gate is so named because if 0 is called 'false' and 1 is called 'true' the gate acts in the same way as the logical 'and' operator the following illustration and table show the circuit symbol and logic combinations for an and gate in the symbol the input terminals are at left and the output terminal is at right the output is 'true' when both inputs are 'true' otherwise the output is 'false' exemple 167 And.And.

To reverse the direction of rotation of a shunt type parallel field dc electric ?

Question 27-12 : Reverse the polarity of either the stator or the rotor reverse the polarity of the motor connections change the connections from shunt to series connect a phase shift capacitor to the field circuit

Changing the polarity of the current would change the direction of the field around the conductor whilst leaving the polarity of the main field unchanged exemple 171 Reverse the polarity of either the stator or the rotor.Reverse the polarity of either the stator or the rotor.

The power required for field excitation of the main rotor in modern constant ?

Question 27-13 : The voltage regulator an excitation alternator with a permanent magnet generator a battery an ac generator

When a brushless generator's rotor is initially driven by the csd unit a permanent magnet generator induces an ac voltage into the pilot output the ac voltage is then full wave rectified and fed to the main exciter by way of the voltage regulator the three phase winding on the rotor now has a voltage induced in it which is fed to the dc main field by way of a three phase rectifier network . the dc main field rotates and induces a voltage in the ac output windings which at the same time increases the output of the pilot exciter . this sequence of events continues until the generator reaches its regulated output voltage the output is typically 200/115 volts three phase 400 hz exemple 175 The voltage regulator.The voltage regulator.

The ignition system generally used for small aircrafts is a ?

Question 27-14 : High tension system battery ignition system high intensity system low tension system

.the sole purpose of the ignition system is to supply a high energy spark at the right moment thereby igniting the fuel air mixture so that the engine can start its power stroke .the source for the spark comes from the magnetos .in the magneto the magnetic field generates a voltage in the coil which is transformed to a higher voltage by a secondary coil with much more windings than the primary coil a breaker contact in the primary coil circuit interrupts the flowing current and this interruption causes the magnetic field to collapse thereby generating a very high peak voltage in the secondary coil this peak voltage is then conducted to the correct spark plugs by the distributor and high voltage leads exemple 179 High tension system.High tension system.

Because of the connection in parallel of electrical equipments on an ac bus bar ?

Question 27-15 : Decreases the bus bar current consumption increases the bus bar voltage decreases the bus bar voltage increases the bus bar current consumption

In parallel ac current is shared between the different electrical equipments connected on the bus bar .if you disconnect one of them bus bar current consumption will be reduced exemple 183 Decreases the bus bar current consumption.Decreases the bus bar current consumption.

Regarding 1 a fuse and 2 a circuit breaker ?

Question 27-16 : 1 is not resettable 2 is resettable 1 is resettable 2 is not resettable 1 is not suitable for high currents 2 is suitable for high currents 1 is suitable for high currents 2 is not suitable for high currents

exemple 187 (1) is not resettable, (2) is resettable.(1) is not resettable, (2) is resettable.

Regarding ohm's law ?

Question 27-17 : The current in a circuit is directly proportional to voltage the current in a circuit is directly proportional to the resistance of the circuit the power in the circuit is inversely proportional to the square of the current the current in a circuit is inversely proportional to voltage

exemple 191 The current in a circuit is directly proportional to voltage.The current in a circuit is directly proportional to voltage.

When the ac generators are connected in parallel the reactive loads are ?

Question 27-18 : Excitation current frequency or load controller voltage controller torque of the constant speed drive csd

If generators are to be paralleled frequency is adjusted by adjusting csd output torque to balance the real load and the reactive loads are trimmed by adjusting the excitation current from the voltage regulator exemple 195 Excitation current.Excitation current.

Generators when connected to the same bus bar are usually connected ?

Question 27-19 : In parallel mode in series mode dependent on the type of generator dependent on the type of engine

exemple 199 In parallel mode.In parallel mode.

The advantages of nickel cadmium compared with lead acid batteries are .1 ?

Question 27-20 : 3 4 1 3 1 2 2 4

exemple 203 3, 4.3, 4.

Static dischargers .1 are used to set all the parts of the airframe to the ?

Question 27-21 : 2 4 5 1 2 5 1 3 4 3 4 5

We are not looking to set all the parts of the airframe to the same electrical potential we are looking to maintain the electrical airframe potential at around 10000 volts via the static dischargers by providing a path for the electrons .example of static dischargers on a wing . 810..without static dischargers the electrical airframe potential would rise up to a value 10 times higher and would disturb and/or damage the onboard equipment exemple 207 2, 4, 5.2, 4, 5.

Assuming the initiating cause is removed which of these statements about ?

Question 27-22 : I is incorrect ii is correct i is incorrect ii is incorrect i is correct ii is incorrect i is correct ii is correct

exemple 211 I is incorrect, ii is correct.I is incorrect, ii is correct.

Assuming the initiating cause is removed which of these statements about ?

Question 27-23 : I is correct ii is correct i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

exemple 215 I is correct, ii is correct.I is correct, ii is correct.

The diagram shown in annex represents a twin engine aeroplane electrical system ?

Question 27-24 : 1 and 2 5 and 6 3 and 4 1 and 3

Img878.each generator has its own busbar with non essential services connected to it or those that don't matter if it fails both are ultimately connected in parallel to a central combining busbar which carries the essential services batteries are located on the hot bus 1 and hot bus 2 providing a source of power if both generators fail exemple 219 1 and 2.1 and 2.

Electrical work measurement unit in the international system of units si is ?

Question 27-25 : Joule watt ohm ampere

Unit of force the unit of force in the mks metre kilogram second system is the force which gives to a mass of 1 kilogram an acceleration of 1 metre per second per second . joule unit of energy or work the joule is the work done when the point of application of 1 mks unit of force newton moves a distance of 1 metre in the direction of the force . watt unit of power the watt is the power which in one second gives rise to energy of 1 joule . ampere unit of electric current the ampere is that constant current which if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed 1 metre apart in vacuum would produce between these conductors a force equal to 2 x 10&8722 7 mks unit of force newton per metre of length . ohm unit of electric resistance the ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt applied to these points .produces in the conductor a current of 1 ampere the conductor not being the seat of any electromotive force exemple 223 Joule.Joule.

If two constant frequency ac generators are operating independently then the ?

Question 27-26 : Is unimportant must be synchronised must be 120° out of phase must be 240° out of phase

exemple 227 Is unimportant.Is unimportant.

The logic symbol shown represents assuming positive logic . 880 ?

Question 27-27 : An invert or not gate a nand gate a nor gate an exclusive gate

A logic gate is an elementary building block of a digital circuit most logic gates have two inputs and one output at any given moment every terminal is in one of the two binary conditions low 0 or high 1 represented by different voltage levels the logic state of a terminal can and generally does change often as the circuit processes data .there are seven basic logic gates and or xor not nand nor and xnor .a logical inverter sometimes called a not gate to differentiate it from other types of electronic inverter devices has only one input it reverses the logic state . 881 exemple 231 An invert or not gate.An invert or not gate.

The connection in parallel of two 12 volt/40 amp hours batteries will create a ?

Question 27-28 : 12 volt/ 80 amp hours 24 volt/ 40 amp hours 24 volt/ 80 amp hours 12 volt/ 40 amp hours

Battery packs achieve the desired operating voltage by connecting several cells in series with each cell adding to the total terminal voltage .24 volt / 40 amp hours .parallel connection attains higher capacity for increased current handling as each cell adds to the total current handling .12 volt/ 80 amp hours .in parallel we increase the flow in series we increase tension exemple 235 12 volt/ 80 amp hours.12 volt/ 80 amp hours.

The capacity of a battery is the ?

Question 27-29 : Amount of ampere hours that a fully charged battery can supply number of cycles charging and discharging that a battery can withstand without deterioration of its cells no load voltage of the battery multiplied by its rated output current intensity withstood by the battery during charging

exemple 239 Amount of ampere hours that a fully charged battery can supply.Amount of ampere hours that a fully charged battery can supply.

The frequency of the current provided by an alternator depends on ?

Question 27-30 : Its rotation speed its phase balance its load the strength of the excitation current

Direct current generators are connected ?

Question 27-31 : In parallel to provide maximum power in parallel to provide maximum voltage in series to provide maximum voltage in series to provide maximum power

Generators run most efficiently when loaded to their rated capacity therefore when load demand increases one or more generators can be connected in parallel to provide more power this is the only way to reach maximum power with dc generators exemple 247 In parallel to provide maximum power.In parallel to provide maximum power.

When carrying out a battery condition check using the aircraft's voltmeter ?

Question 27-32 : A load should be applied to the battery in order to give a better indication of condition no load should be applied to the battery because it would reduce the voltage the battery should be isolated the load condition is unimportant

exemple 251 A load should be applied to the battery in order to give a better indication of condition.A load should be applied to the battery in order to give a better indication of condition.

When a battery is almost fully discharged there is a tendency for the ?

Question 27-33 : Voltage to decrease under load voltage to increase due to the current available current produced to increase due to the reduced voltage electrolyte to 'boil'

exemple 255 Voltage to decrease under load.Voltage to decrease under load.

To ensure correct load sharing between ac generators operating in parallel ?

Question 27-34 : Both real and reactive loads must be matched the matching of loads is unimportant only reactive loads need to be matched only real loads need to be matched

exemple 259 Both real and reactive loads must be matched.Both real and reactive loads must be matched.

The frequency of an ac generator is dependent on the ?

Question 27-35 : Number of pairs of poles and the speed of the moving part number of individual poles only field strength and the speed of the moving part number of individual poles and the field strength

The frequency of the induced ac current depends on the revolution of the rotor since rate of revolution is revolutions per minute rpm and frequency is expressed as cycles per second the frequency of the induced ac current will be the rate of revolution of the rotor divided by 60 .in addition to above if two magnets are used two pole pairs the frequency is doubled tripled for three thus putting all of this in a formula we get .frequency hz = rpm x number of pole pairs / 60 exemple 263 Number of pairs of poles and the speed of the moving part.Number of pairs of poles and the speed of the moving part.

If a current is passed through a conductor which is positioned in a magnetic ?

Question 27-36 : A force will be exerted on the conductor the intensity of the magnetic field will decrease the current will increase there will be no effect unless the conductor is moved

When a current is passed through the wire wrapped around a conductor its magnetic field penetrates the conductor and causes the domains to turn aligning parallel to the magnetic field so their tiny magnetic fields add to the wire's field creating a large magnetic field that extends into the space around the magnet . the larger the current passed through the wire coil the more the domains align and the stronger the magnetic field is exemple 267 A force will be exerted on the conductor.A force will be exerted on the conductor.

The alternators when connected are usually connected ?

Question 27-37 : In parallel mode in series mode dependant on the type of generator dependant on the type of engine

exemple 271 In parallel mode.In parallel mode.

The capacity of an accumulator is ?

Question 27-38 : The quantity of electricity that the battery can supply during discharge the number of cycles charging and discharging that a battery can withstand without deterioration of its cells the no load voltage of the battery multiplied by its rated output current the intensity withstood by the battery during charging

.a battery's capacity is the quantity of electricity that it can supply during discharge the more electrolyte and electrode material there is in the cell the greater the capacity of the cell .a small cell has less capacity than a larger cell with the same chemistry and they develop the same open circuit voltage .because of the chemical reactions within the cells the capacity of a battery depends on the discharge conditions such as the magnitude of the current which may vary with time the allowable terminal voltage of the battery temperature and other factors the available capacity of a battery depends upon the rate at which it is discharged if a battery is discharged at a relatively high rate the available capacity will be lower than expected exemple 275 The quantity of electricity that the battery can supply during discharge.The quantity of electricity that the battery can supply during discharge.

The moving part in an ac generator is usually referred to as the ?

Question 27-39 : Rotor slip ring stator oscillator

exemple 279 Rotor.Rotor.

The purpose of bonding the metallic parts of an aircraft is to ?

Question 27-40 : Provide safe distribution of electrical charges and currents prevent electrolytic corrosion between mating surfaces of similar metals isolate all components electrically and thus make the static potential constant provide a single earth for electrical devices

.the single earth return uses the aircraft structure as a return path if the component is not electrical it does not need a return path but still requires bonding to equalise potential difference in the event of static build up this is why the answer provide a single earth for electrical devices is false exemple 283 Provide safe distribution of electrical charges and currents.Provide safe distribution of electrical charges and currents.

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