Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
A comprehensive set of questions and answers related to alternating currents (ac) circuits. It covers fundamental concepts, calculations, and applications of ac circuits, including topics like power triangle, transformers, capacitive and inductive reactance, phase angles, and impedance. Suitable for students studying electrical engineering or related fields.
Typology: Exams
1 / 18
This page cannot be seen from the preview
Don't miss anything!
According to the power triangle, the apparent power is___. - ANSWER✔✔Greater than the true power Which of the following uses electromagnetic induction to transfer electrical energy from one circuit to another? - ANSWER✔✔Transformer What is the step-down turns ratio of a transformer with 200 turns in the primary and 100 turns in the secondary? - ANSWER✔✔2:
Opening the secondary of a CT under load will cause a dangerous level of___. - ANSWER✔✔induced high voltage Which of the following is true of the current in a capacitive circuit? - ANSWER✔✔It leads the voltage. In sine wave terminology, the average value is___. - ANSWER✔✔0. x peak value In AC circuits containing only resistance,. - ANSWER✔✔All DC rules and laws apply, including Ohm's law If the area of the plates of a capacitor is increased, the amount of capacitance. - ANSWER✔✔Increases The self-induced voltage across in inductance is equal to the change in___. - ANSWER✔✔Current with respect to time
Given: An AC circuit containing resistance only. What is the current flow if the resistance is 15 ohms and the voltage is 150v? - ANSWER✔✔10A The current in inductive circuit___. - ANSWER✔✔Lags the voltage Unless otherwise noted, the calculations in AC circuits use___. - ANSWER✔✔Rms values When frequency decreases, capacitive reactance___. - ANSWER✔✔Increases Given: A transformer has 200 turns in the primary, 100 turns in the secondary, and 150V AC applied to the primary. What is the voltage across the secondary? - ANSWER✔✔75V AC
Transformers in which the primary and secondary voltages are 180 out of phase are known as___. - ANSWER✔✔Unlike-wound transformers Maximum voltage is generated by rotating wire when the conductor is moving___. - ANSWER✔✔Across the field at 90° If the time for one cycle is 0.1 second, the frequency is___. - ANSWER✔✔10 Hz If the phase angles of two sine waves are both 0 degrees then the waves___. - ANSWER✔✔Are in phase Calculate the true power in a 2A series RL circuit with a 100 ohms resistor. - ANSWER✔✔400W Inductive reactance increases as the___. - ANSWER✔✔Frequency increases
ANSWER✔✔Apparent power In a parallel LC circuit, the voltage across the branches is___. - ANSWER✔✔The same as the applied voltage Which of the following coils is likely to show the lowest inductance? - ANSWER✔✔A coil with a narrow coil, long core, non-magnetic core and few turns Which of the following conditions exist in a circuit of pure resistance? - ANSWER✔✔Voltage and current in phase What is the peak voltage in a circuit with an rms voltage of 120VAC? - ANSWER✔✔170 volts Which of the following conditions exist in a circuit of pure inductance? - ANSWER✔✔The voltage and current are 90 degrees out of phase.
The power factor in a circuit with a resistance of 50Upper Omega and an impedance of 100Upper Omega is - ANSWER✔✔0. A power factor is not an angular measure, but a numerical ratio with a value between 0 and 1, equal to the - ANSWER✔✔cosine of the phase angle A transformer with 10 turns in the primary and two turns in the secondary has a turns ratio of (ratio is primary/secondary) - ANSWER✔✔ 5 Capacitance is measured in - ANSWER✔✔farad or micro farad The total capacitance of two 5uf capacitors and one 10uf capacitor in parallel is - ANSWER✔✔20uf The two windings of a conventional transformer are known as the -
An electric current always produces - ANSWER✔✔magnetic field The total capacitance of two 15uF capacitors connected in parallel is - ANSWER✔✔30uF The number of cycles an alternating electric current undergoes per second is known as - ANSWER✔✔Frequency When the current increases in an AC circuit, what role does inductance play? - ANSWER✔✔reduces current Reactance increases with an increase in - ANSWER✔✔Inductance Which of these items determines the amount of voltage induced in a moving conductor? - ANSWER✔✔Speed of conductor, rate of movement and strength of magnetic field
The greatest amount of voltage is induced when the conductor is moving _____ to the magnetic field. - ANSWER✔✔perpendicular What is the frequency of a waveform that occurs 500 times in 10 seconds? (500/10) - ANSWER✔✔50Hz Given frequencies of 60Hz and 50Hz, which has the shortest period? - ANSWER✔✔60Hz (higher the number the shortest period) What is the peak value of a waveform that has a peak-to-peak value of 150 volts? - ANSWER✔✔75volts (half value) The symbol for phase angle is - ANSWER✔✔Theta vector straight line of a sine wave means - ANSWER✔✔voltage and current in phase
If a 15- and a 35-microfarad capacitor are connected in parallel, the total capacitance is _____ microfarads. - ANSWER✔✔ 50 A variable capacitor is used to tune a radio to the desired station. At the low end of the AM band (550kHz), will the capacitive reactance (XC) be higher or lower than it is at the high end of the band (1440kHz)? - ANSWER✔✔Higher Total opposition to current flow in an AC circuit is called _____. - ANSWER✔✔impedance If the resistance in a series RL circuit is greater than the inductance, the phase angle will be _____. - ANSWER✔✔less than 45 degrees Which of the following statements applies to a parallel RC circuit? - ANSWER✔✔The voltages across the branches are in phase.
In a series LC circuit, the capacitor drops 170 volts and the inductor drops 50 volts. The total voltage is _____ volts. - ANSWER✔✔ 120 When resistance is added to an AC circuit containing a capacitor, current will lead voltage by an angle between _____. - ANSWER✔✔zero and 90 degrees If resistance and capacitive reactance are equal in a series RC circuit, the phase angle will be _____ degrees. - ANSWER✔✔ 45 Apparent power is the _____. - ANSWER✔✔product of source voltage and total current The power factor of a circuit is the ratio of _____. - ANSWER✔✔true power to apparent power
to compare the phase angle between two wave both waves must have the same - ANSWER✔✔frequency one device that requires sawtooth waveform is - ANSWER✔✔oscilloscope what is the voltage (E) in purely resistive circuit with a current draw of 22A and 10 omega resistance? - ANSWER✔✔220V which of the following coils is likely to show highest inductance? - ANSWER✔✔short core, many turns and magnetic core total capacitance of three 10uF capacitors and one 5uF capacitor connected in parallel is - ANSWER✔✔35uF circuit's impedance is represented by the letter - ANSWER✔✔Z
True power is the product of resistor current squared and the - ANSWER✔✔resistance apparent power is the product of the source voltage and the - ANSWER✔✔current reactive power - ANSWER✔✔performs no work power factor of a circuit with resistance of 75 omega and impedance of 150 omega is - ANSWER✔✔. apparent power is the result of the vector addition of the true power and the - ANSWER✔✔reactive power an iron core transformer provides better power transfer than air core transformer - ANSWER✔✔true transformer
