TC Flashcards
A shunt is used in a current meter in order to
Increase the current range of the instrument
What are the two Kirchoff laws?
The sum of the currently entering a point is equal to the sum of the current leaving the point.
The sum of the voltage drops around a circuit equals the voltage of the source.
A Milli volt metre is calibrated to measure between voltages of
More than 1mV, but less than 1V
A DC voltmeter should be connected:
Negative lead to the negative side circuit, positive lead to the positive side of the circuit
Capacitor reactants is measured in
Ohms
In a parallel, RL circuit, Ir and Il are
90° out of phase
In a parallel, RL circuit, when the phase angle is small, the PF is
High
In a certain capacitor, if the spacing between the plate is increased, the
Capacity is decreased
A shading ring is used in a AC magnetic contactor to
Prevent hum and chatter
I wattmeter properly connected in an AC circuit with inductance, and negligible resistance, will read
Practically zero
Which transformer should have the secondary winding short-circuited when the primary is energized and there is no secondary load connected
Current transformer [CT]
The closure voltage of a Delta connected transformer secondary should be nearly
0 V
An open circuit test on a transformer is used to measure its
Iron losses (core losses)
A short circuit test on a transformer is used to measure its
Copper losses
In a three lamp, ground fault, detector system, which of the following occurs if one line becomes solidly grounded?
Two lamps go bright, one goes dim
When parallelling alternators and using the ‘three dark method’, the lights are seen to blink on and off rapidly in unison. What is the problem?
The frequency of one alternator is too low
The greatest drop in output voltage will occur if full load taken from an alternator at
A lagging power factor
The speed of a synchronous motor depends upon
Number of poles and supply frequency
Torque angle for synchronous motors is defined as the angle between
Stator pole and rotor pole
The torque angle of a synchronous motor is affected by the
Load
The power factor of an overexcited synchronous motor would be
Leading
The direction of rotation of a three phase induction motor is
The same direction of the rotating magnetic field
To dynamically break an induction motor, it is necessary to
Apply DC to the stator
If two leads of the rotor winding on a three phase wound rotor motor are interchanged, the
Rotation would remain the same
