Description : What is the relation between voltage and current in AC circuit containing only inductance?
Last Answer : Current (I) is lags behind the voltage by 90°. I = V/XL amps. XL = 2πfL ohms. P = I * V * cosϕ watts. (Where cosϕ is 90 because current lags behind voltage by 90°. So cosϕ 90° = 0) ∴ P = I * V * 0 = 0 watts.
Description : What is the relation between voltage and current in AC circuit containing only resistance?
Last Answer : Current (I) is in-phase with the voltage. I = V/R amps. P = I * V * cosϕ or I2 R watts. (Where cosϕ is zero because the voltage and current are in-phase. So cosϕ 0° (zero) = 1)
Description : Capacitance in an AC circuit will _____________. A. stop current flow once the capacitor is fully charged B. allow current flow in only one direction C. oppose any change in circuit voltage D. rectify the current
Last Answer : Answer: C
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
Last Answer : Answer: A
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 : 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 : 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 : 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 : 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 : A battery is connected to a circuit containing three resistors in parallel. The values of the three resistors are 2 ohms, 3 ohms, and 6 ohms. What is the voltage of the battery if the total circuit current is 12 amps? A. 2 volts B. 6 volts C. 12 volts D. 24 volt
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 : Which of the following statements is true concerning a stepdown transformer in an operating AC power circuit? A. Voltage and current will both be increased. B. Voltage and current will both be decreased C. Voltage decreases as current increases. D. Voltage increases as current decreases.
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 an AC circuit, the inductive reactance of a coil varies with the _______________. A. resistance of the circuit B. frequency of the circuit C. voltage of the circuit D. current of the circuit
Description : A transformer in an electric circuit serves to ____________. A. generate its own electrical power B. transform electrical energy into mechanical energy C. increase or decrease circuit voltage as required D. convert AC current to DC current
Description : An a.c series circuit has resistance of 10ohm, inductance of 0.1H and capacitance of 10µf, voltage applied to circuit is 200V. find (i) Resonant frequency (ii) Current at resonance (iii) Power at resonance
Last Answer : Solution: For RLC series circuit
Description : To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will _____.
Last Answer : To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will decrease.
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 : 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 : In AC Circuit Theory, the term that replaces the resistance is: w) inductance x) capacitance y) impedance z) reactance
Last Answer : ANSWER: Y -- IMPEDANCE
Description : The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains _____________. A. a magnetic operating coil B. normally open line contacts C. thermal-overload protection D. a momentary-contact start button
Description : Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop
Description : An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. ... between the armature and the bus D. cause high currents to be induced in the field windings
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Description : When securing an AC generator, you should FIRST ___________. A. open the generator circuit breaker B. switch the voltage regulator to 'manual' C. decrease the field excitation to minimum D. reduce the load on the unit
Description : State the voltage and current relation in star and delta connection.
Last Answer : In star connection line current is equal to the phase current and line voltage is √3 times that of phase voltage. In delta connection line voltage is equal to the phase voltage and line current is √3 times that of phase current.
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 : What is the purpose of CVT (capacitance voltage transformer)?
Last Answer : Purposes of CVT are a. To indicate if line is charged or not. b. To synchronize grid with generator. c. For power line communication and carrier tripping.
Description : As shown in the illustration, the circuit has been on the line for several days when component 'E1' burns out. The operator receives an alarm, switches over 'B' to energize the standby ... than required for the circuit therefore limiting the current through the alarm relay which will not pick up
Description : The time constant of the capacitance circuit is defined as the time during which voltage?
Last Answer : The time constant of the capacitance circuit is defined as the time during which voltage rises to 63.2% of its final steady value.
Description : In the schematic of the electrical circuit shown in the illustration, what is the value of the total capacitance, when compared to the value of equal individual capacitors? EL-0038 A. Equal B. Half C. Double D. Squared
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 : What is the formula to find the capacitance in a circuit?
Last Answer : C = Q/E farad.
Description : What is the resultant capacitance in series and parallel circuit?
Last Answer : In series circuit the resultant capacitance 1/CT = 1/c1+1/c2 + 1cn farad. In parallel circuit the resultant capacitance CT = c1 + c2 + cn farad.
Description : If reading AC current with the illustrated device and unsure of the range as a precaution , the first step should be to _________. EL-0047 A. secure power and test for voltage B. disconnect the ... resistance and use Ohm's law to calculate current D. unable to safely measure current with the device
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 : Which is a function of the voltage regulators used with AC generators? A. To cut out generators when they are no longer required. B. To cut in additional generators automatically as ... between generators operating in parallel. D. To divide reactive current between generators operating in parallel.
Description : A switchboard for an AC electrical system requires the use of which of the following devices? A. Frequency meter. B. Ohmmeter. C. Induction voltage regulator. D. Current transformer governor.
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 : A testing device called a 'growler' is being used to locate a shorted coil in the stator of an AC electrical machine. When the 'feeler' is moved over a slot containing the shorted coil _____________. ... . the meter needle will be deflected to zero D. the meter needle will be deflected to full-scale
Description : Instantaneous voltage and instantaneoss current in an L-R circuit in AC is V=100sin (100)t and `i=10sin(100t-pi//4)`. Match the following table, `{:(,
Last Answer : Instantaneous voltage and instantaneoss current in an L-R circuit in AC is V=100sin (100)t and `i=10sin(100t ... power in one cycle",(S),"None"):}`
Description : When an AC voltage, of variable frequency is applied to series L-C-R circuit, the current in the cirucit is the same at 4kHz. The current in the cirui
Last Answer : When an AC voltage, of variable frequency is applied to series L-C-R circuit, the current in the cirucit ... is maximum at (x)kHz. Find the value of x
Description : In a simple dc circuit, voltage equals resistance multiplied by current. This is also considered true in an AC circuit if the what values of the current and voltage are used.
Last Answer : ANSWER: ROOT MEAN SQUARE (RMS) VALUES
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 : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker