Description : AC and DC generators are similar in that they _____________. A. both generate alternating voltages B. both rectify the voltage before delivery C. are constructed at the same physical size for the same kilowatt rating D. both supply three-phase power
Last Answer : Answer: A
Description : An AC circuit has capacitance arranged in series. If the line voltage remains constant, the capacitive reactance value can be varied by changing the _____________. A. line frequency B. resistance C. number of commutating poles D. number of interpoles
Description : The open-circuit voltage of a fully charged lead-acid battery cell is _____________. A. 1.5 volts B. 1.8 volts C. 2.0 volts D. 2.3 volts
Last Answer : Answer: C
Description : Capacitance is the property of an electric circuit opposing a change in the _____________. A. current in the circuit B. voltage in the circuit C. inductance in the circuit D. resistance in the circuit
Last Answer : Answer: B
Description : Basically, a magnetic amplifier is a saturable reactor with the addition of _____________. A. AC to the bias winding B. variable capacitance to all windings C. eddy current protectors D. a rectifier in the load circuit
Last Answer : Answer: D
Description : What is the relation between voltage and current in AC circuit containing only capacitance?
Last Answer : Current (I) is leading the voltage by 90°. I = V/XC amps. XC = 1/2πfC ohms. P = I * V * cosϕ watts. (Where cosϕ is 90 because current is leading the voltage by 90°. So cosϕ 90° = 0) ∴ P = I * V * 0 = 0 watts.
Description : To properly use a hook-on-type volt/ammeter to check current flow, you must FIRST _____________. A. de-energize the circuit to allow connection of the instrument in series B. hook the jaws ... test leads to the appropriate terminals D. short the test leads and calibrate the instrument to zero
Description : If a capacitance is charged by a square wave current source, then the voltage across the capacitor will be (a) Square wave (b) Step function (c) Triangular wave (d) Zero
Last Answer : If a capacitor is charged by a square wave current source, the voltage across the capacitor is : triangular wave
Description : You are attempting to parallel two AC generators and the synchroscope pointer is revolving slowly in the fast direction. You should _____________. A. use the governor control switch to adjust the incoming ... the 0° position D. use the field rheostat to adjust the speed of the incoming machine
Description : AC circuits develop resistance, inductance, and capacitance. The inductive reactance of a circuit is expressed in _____________. A. ohms B. mhos C. henrys D. farads
Description : AC circuits possess characteristics of resistance, inductance, and capacitance. The capacitive reactance of a circuit is expressed in _____________. A. ohms B. mhos C. henrys D. farads
Description : The timer element of a reverse power relay cannot be energized unless _____________. A. one generator is fully motorized B. the movement of the disk is damped by a permanent magnet C. the power flow is the same as the tripping direction D. the power flow is the opposite to the tripping direction
Description : Inductance is the property of an electric circuit that _____________. A. opposes any change in the applied voltage B. opposes any change in the current flow through the circuit C. aids any changes in the applied voltage D. aids any changes in the current through the circuit
Description : A capacitor and a coil are connected in series. The capacitor is charged and allowed to discharge through the coil. The current that will then flow through the capacitor-coil combination will do ... but diminish steadily to zero z) oscillate at high frequency at first but then at slower frequency
Last Answer : ANSWER: Y -- OSCILLATE BUT DIMINISH STEADILY TO ZERO
Description : If an AC generator experiences voltage failure, the cause may be _____________. A. an open in the field circuit B. the brushes shifting out of the neutral plane C. excessive locked-rotor current D. a rotating slip ring
Description : You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0°. If you close the circuit breaker at this moment _____________. A. the incoming ... hazardous condition will be created by the incoming machine being at a higher frequency than the bus
Description : When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is _____________. A. lagging B. leading C. maximum D. minimum
Description : When the voltage and the current developed in an AC circuit reach their peak values at the same time, the power factor is considered to be _____________. A. lagging B. leading C. unity D. infinity
Description : In the flow of one cycle of single phase AC current past any given point in a circuit, the maximum current peak occurs _____________. A. one time B. two times C. three times D. four times
Description : When a megohmmeter is used to test the dielectric strength of wire insulation, the initial dip of the pointer toward 'zero' is caused by _____________. A. good insulation B. the leakage of ... of dirty insulation C. the capacitance of the circuit D. the dielectric absorption effect of the insulation
Description : When troubleshooting electronic equipment, you should use a high impedance multimeter ________________. A. to prevent excess current flow through the meter that would damage it B. for AC measurements only ... being tested D. so as not to load down the circuit and obtain erroneous voltage readings
Description : What is the capacitance when a capacitor passes a current of 31.43 mA when supplied with 40 V AC with a frequency of 1000 Hz? A) 0.125 F B) 0.125 μF C) 1257.2 μF D) None of these
Last Answer : What is the capacitance when a capacitor passes a current of 31.43 mA when supplied with 40 V AC with a frequency of 1000 Hz? A) 0.125 F B) 0.125 μF C) 1257.2 μF D) None of these
Description : The value of the capacitance depends upon the________________? A.voltage applied B. thickness of the capacitor plates C. geometry of the capacitor D. dinsity of the capacitor plates
Last Answer : Ans: C
Description : In accordance with Coast Guard Regulations (46 CFR), each battery operated relay-controlled lantern must _____________. A. be readily portable B. contain a dry cell battery having a minimum capacity of ... automatic battery charger to maintain the battery in a fully charged state D. all of the above
Description : The freezing point of the electrolyte in a fully charged lead-acid battery will be _____________. A. higher than in a discharged battery B. lower than in a discharged battery C. the same as in a discharged battery D. higher than in a discharged battery, but the specific gravity will be less
Description : In the illustrated circuit, one advantage of the capacitor coupling over direct coupling is ____________. EL-0048 A. as the frequency decreased the capacitive reactance (Xc) increases B. the amplifier becomes ... of the signal while it isolates the biasing of each stage. D. good frequency response.
Description : You are attempting to parallel two AC generators, and the synchroscope pointer is revolving fast in the clockwise direction. This indicates that the frequency of the incoming machine is _____________. A. higher ... at any pointer position D. the same as the bus frequency but out of phase with it
Description : You are attempting to parallel two AC generators, and the synchroscope pointer is revolving in the fast direction. This indicates that the frequency of the incoming machine is _____________. A. higher ... the same as the bus frequency and the circuit breaker may be closed at any pointer position
Description : You are attempting to parallel two AC generators and the synchroscope pointer is revolving in the slow direction. This indicates that the frequency of the incoming machine is _____________. A. higher than ... same as the bus frequency, and the circuit breaker may be closed at any pointer position
Description : When the voltage remains constant, and the resistance increases in a series circuit, current flow _____________. A. decreases B. remains the same C. increases D. increases by the square
Description : When the voltage remains constant and the resistance is increased in a series circuit, the flow of current _____________. A. increases by the square of the original value B. increases C. remains the same D. decreases
Description : If the resistance of a circuit is cut in half and the applied voltage is kept constant, the current flow will be _____________. A. doubled B. quadrupled C. unchanged D. cut in half
Description : A low-voltage protection circuit is used in electric motor starting equipment to _____________. A. trip circuit contactors when the motor overspeeds due to low voltage B. trip circuit ... voltage without manually resetting D. prevent the motor from restarting automatically on restoration of voltage
Description : A capacitor of capacitance 50 micro farads is charged to a potential difference of 200 Volts. Find out energy stored in the condenser?
Last Answer : A capacitor of capacitance 50 micro farads is charged to a potential difference of 200 Volts. Find out energy stored in the condenser? 1 joule
Description : The frequency of an AC generator is controlled by the _____________. A. rheostat B. governor C. exciter D. capacitor
Description : The formula for computing impedance in a series circuit containing resistance, capacitance, and inductance is _____________. [ NOTE: the symbol * stands for 'multiplied by' ] A. Z = RT + XL + XC B. Z = R + XL - XC C. Z * Z = R * R + (XL - XC) * (XL - XC) D. Z = R * R + (XL * XC) - (XL * XC)
Description : A lead-acid battery is considered fully charged when the ______________. A. electrolyte gasses freely B. battery charger ammeter indicates a positive reading C. terminal voltage reaches a constant value at a ... cells reaches the correct value and no longer increases over a period of 1 to 4 hours
Description : An instantaneous-trip-type fuse will _____________. A. open as soon as the load current exceeds its set point B. allow a preset delay between overcurrent and melting C. open a circuit by using a time delay element with a magnetic trip D. reset itself when the overcurrent is corrected
Description : Capacitor is fully charged if potential difference is equal toA. e.m.f B. current C. resistance D. power
Last Answer : e.m.f
Description : Which of the listed battery charging circuits is used to maintain a wet-cell, lead-acid, storage battery in a fully charged state during long periods of disuse? A. Normal charging circuit B. Quick charging circuit C. Trickle charging circuit D. High ampere charging circuit
Description : Equal power factors on paralleled AC generators are maintained by an automatic _____________. A. voltage regulator B. reverse power relay C. reverse current relay D. governor control switch
Description : The electrical supply applied to the anodes shown in the illustration is _____________. EL-0090 A. low voltage, high current DC B. low voltage, high current AC C. high voltage, low current DC D. high voltage, low current AC
Description : Shading coils are installed on AC full-voltage starters to _____________. A. eliminate contact chatter B. dissipate opening contact arcs C. delay current build up in the holding coil D. protect the motor windings from momentary starting current overload
Description : The reactive power drawn by a motor from an AC generator is the power which is _____________. A. used to establish the magnetic field of the motor B. lost in overcoming friction in the ... by current flow through the windings D. transmitted directly through the rotor shaft to perform useful work
Description : When measuring AC current flow, you must always connect the meter _____________. A. in series with the power source and load B. in parallel with the power source and load C. insuring correct polarity D. using the lowest range possible to prevent instrument damage
Description : In accordance with Coast Guard Regulations (46 CFR), a circuit breaker located in the machinery space and installed in a 440V AC system must _____________. A. be dependent upon mechanical ... the maximum asymmetrical shortcircuit current available at the point of application D. all of the above
Description : The purpose of DC generator brushes is to _____________. A. neutralize armature reaction B. conduct electric current to an outside circuit C. convert DC current to AC current D. provide excitation to a DC generator
Description : The most inefficient method of voltage reduction from the stand point of power loss, is a/an _____________. A. capacitor in series with the load B. inductor in series with the load C. capacitor and inductor in series with the load D. resistor in series with the load
Description : What happens to current flow in a capacitive circuit when the DC voltage across the capacitor is approximately equal to the source voltage?
Last Answer : Capacitor always charges up to the voltage of source. When the capacitor is charged to same as source voltage then there is no current flowing through the capacitor. The current through the capacitor is called displacement current.
Description : The most practical method of controlling the RPM of a step-speed AC motor is to _____________. A. change input voltage B. vary the number of poles C. vary power factor D. change the number of brushes