The rotating part of a motor/generator is called?
- commutator
- armature
- yoke
What is the purpose of the capacitor used in a single phase AC motor ?
- Changing direction of motor
- Provides a high starting torque
- Smoothing Troque
The controlling phase on a two phase motor is of a ?
- variable amplitude
- fixed amplitude
- direct current
In a two-phase induction motor there are ?
- 2 poles
- 4 poles
- 3 poles
In a synchronous motor, when the motor is running the slip is ?
- 100%
- 5%
- 0%
A capacitor in a single phase motor is to ?
- prevent sparking at the switch
- provide smoothing
- provide a phase shift
Calculate the speed of a 400 Hz, 4 pole machine ?
- 6000 rpm
- 12,000 rpm
- 8000 rpm
A three-phase motor has the windings ?
- 90° apart
- 180°apart
- 120° apart
In an aircraft brushless alternator the armature is ?
- star wound
- delta wound
- in series with the field
In a 2 phase generator, what angle are the phases to each other ?
- 0°
- 180°
- 90°
The SI unit of capacitance is ?
- Farad
- Volt
- Ohm
Germanium and silicon have how many electrons in their outer shell?
- 8
- 6
- 4
A semi-conductor will have?
- two electrons in the outer shell
- four electrons in the outer shell
- eight electrons in the outer shell
The symbol “Ω” represents ?
- Watt
- Ohm
- Volt
An ammeter is always connected in?
- Series
- Parallel
- Neither
A voltmeter is always connected in?
- Series
- Barometer
- Both
Ohm’s law states that ?
- R = V + I
- V = I × R
- I = R × V
Which of the following is 1 Amp?
- 1000 mA
- 1000 kA
- 1000 μA
The S.I. unit of magnetic flux density is the?
- Henry
- Weber
- Tesla
The property of a material to accept lines of flux is called?
- retentivity
- reluctance
- permeability
What is the SI unit of conductance?
- Ohm-metre
- Ohm
- Siemen
What is the SI unit of resistivity ?
- Ohms
- Ohms/metre
- Ohm metre
A thermocouple indicator is basically a type of ?
- millivoltmeter
- milliammeter
- milliohmeter
A battery rated at 40 Ah will supply 200 mA for ?
- 20 hours
- 200 hours
- 5 hours
Two 12V 40 amp hour batteries connected in parallel will produce ?
- 12V 80 ah
- 24V 80 ah
- 24V 40 ah
In a mercury cell the steel casing is ?
- The negative terminal
- the positive terminal
- Neither
The electrolyte in a nicad battery is ?
- Cadmium hydroxide
- Nickel hydroxide
- Potassium hydroxide
A galvanometer measures ?
- megohms
- milliamps
- millivolts
If voltage is 100V, resistance is 25 ohms, what is the current ?
- 2500 amperes
- 0.4 amperes
- 4 amperes
In a balanced Wheatstone bridge, across the centre of the bridge there is?
- Current and voltage at maximum
- No current flow
- No voltage present at either end
Total resistance in a parallel resistor circuit, of R1 and R2 is ?
- 1/RT = 1/R1 + 1/R2
- 1/RT = (R1 * R2) ÷ (R1 + R2)
- RT = 1/R1 + 1/R2
A 47 kilohm resistor has the following colour code ?
- Orange, Violet, Red
- Red, Orange, Yellow
- Yellow, Violet, Orange
The phase difference between current and voltage in a pure inductive circuit is ?
- 0°
- 90°
- 180°
The reactance of a capacitor decreases when ?
- Frequency increases
- Frequency decreases
- Capacitance decreases
When a conductor moves through a magnetic field, an EMF is induced due to ?
- Electromagnetic induction
- Mutual induction
- Electrostatic induction
Lenz’s law states that ?
- Induced current flows only in one direction
- Induced EMF aids the cause producing it
- Induced EMF opposes the cause producing it
In a transformer, eddy current losses can be reduced by ?
- Increasing core size
- Using laminated core
- Using solid iron core
The primary purpose of a rectifier is to ?
- Step up voltage
- Convert DC to AC
- Convert AC to DC
Kirchhoff’s voltage law states that ?
- Total current entering equals current leaving
- Total voltage around a loop equals zero
- Power is equal to VI
The instrument used to measure insulation resistance is?
- Voltmeter
- Megger
- Ohmmeter
One Picofarad is ?
- 1 * 10-6 farad
- 1 * 10-12 farad
- 1 * 1012 farad
Magnetic inclination is the least at the ?
- poles
- equator
- isoclines
The unit of flux is the ?
- Ampere turns / metre
- Ampere turns
- Weber
The symbol for flux density is ?
- B(capital)
- H(capital)
- ø(phy)
If the rate of change of current is halved, mutual inductance will ?
- Halve
- Stay the same
- Double
The electromagnetic brake coil in an actuator would be energised ?
- only when the actuator is running
- all the time in flight
- only at the instant of starting and stopping
One purpose of a growler test is to determine the presence of ?
- An out-of-round commutator
- A broken field lead
- A shorted armature
A series wound DC motor, the field has ?
- many turns of thin wire
- few turns of thick wire
- few turns of thin wire
The voltage output of a generator is controlled by ?
- varying the current of the output
- varying the resistance of the output
- varying the current of the field
A 6 pole wave-wound generator has ?
- 2 brushes
- 3 brushes
- 6 brushes
Commutator ripple can be reduced by ?
- a resistor in series with the armature
- increasing generator frequency
- the use of a ripple filter
A shunt motor ?
- is constant speed
- has high starting torque
- gives constant torque with variations in speed