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A collection of questions and answers related to the alternating currents module 1 exam. It covers various concepts, including voltage, current, capacitance, inductance, reactance, and power in ac circuits. Useful for students preparing for the exam, as it offers practice questions and their solutions.
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A circuit has a peak voltage of 275V. What is the average voltage value? - ANSWER✔✔175V Each of three equal capacitors in series has___. - ANSWER✔✔one-third the applied voltage The formula for inductive reactance is___. - ANSWER✔✔XL=2piefL
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
In sine wave terminology, the average value is___. - ANSWER✔✔ 0 .637 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.
The self-induced voltage across in inductance is equal to the change in___. - ANSWER✔✔Current with respect to time Given: A 30-microfarad capacitor in parallel with a 15-microfarad capacitor. The total capacitance is___. - ANSWER✔✔ 45 Which of the following opposes any change in circuit current? - ANSWER✔✔Inductance "ELI the ICE MAN" is used to remember___. - ANSWER✔✔Phase relationships that exist between voltage and current in an inductive circuit
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
The power factor can be defined as the ratio of true power to___. - ANSWER✔✔Apparent power For a given frequency, the capacitive reactance decreases with___. - ANSWER✔✔Increasing capacitance In a circuit that has both capacitance and resistance, the current will lead the voltage___. - ANSWER✔✔By some angle between 0° and 90° If the vector diagram of two AC waveforms is a right angle, then the waves___. - ANSWER✔✔Are 90° out of phase
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
1 ANSWER✔✔impedance The opposition to current flow offered by the capacitance of a circuit is known as - ANSWER✔✔Capacitive Reactance The total capacitance of two 15uF capacitors in series is - ANSWER✔✔7.5uF The true power in a circuit with 4A through a 50 Omega resistor is - ANSWER✔✔800W An electric current always produces - ANSWER✔✔magnetic field
1 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
1 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?
1 vector straight line of a sine wave means - ANSWER✔✔voltage and current in phase non-sine waves - ANSWER✔✔sawtooth, rectangular and square waves In a purely resistive circuit containing one 25-ohm resistor powered by 120VAC, the total current flow is _____ amps. - ANSWER✔✔4. In a purely resistive circuit, the voltage and current will be _____. - ANSWER✔✔in phase
1 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.
1 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
