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ALTERNATING CURRENTS LEVEL 2 MODULE 1
QUESTIONS WITH CORRECT DETAILED
ANSWERS LATEST UPDATE 20 24 - 2025
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 What is the hertz rating of an AC circuit if the frequency is 20 cycles per 1/ second? - ANSWER✔✔40Hz Given: A circuit has an rms voltage of 120VAC. What is the peak-to-peak voltage? - ANSWER✔✔340V A circuit has a peak voltage of 275V. What is the average voltage value? - ANSWER✔✔175V
2 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 Which of the following is true of the current in a capacitive circuit? - ANSWER✔✔It leads the voltage.
4 "ELI the ICE MAN" is used to remember___. - ANSWER✔✔Phase relationships that exist between voltage and current in an inductive circuit 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 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°
5 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°
7 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
8 The two windings of a conventional transformer are known as the - ANSWER✔✔primary and secondary windings In a purely resistive AC circuit where 240V is applied across a 10 - ohm resistor, the amperage is (ohm's law) - ANSWER✔✔24A The total opposition to current flow in an AC circuit is known as - 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
10 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 non-sine waves - ANSWER✔✔sawtooth, rectangular and square waves
11 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 A coil with many turns of wire will induce less voltage than a coil with fewer turns of wire. - ANSWER✔✔False In an inductor, when the voltage waveform is at 270 degrees, the current waveform will be at _____. - ANSWER✔✔zero How much current will flow in a circuit that is supplied by a 60 - Hz, 120-volt source and has a 0.03-henry coil? - ANSWER✔✔10.6A If a 15 - and a 35 - microfarad capacitor are connected in parallel, the total capacitance is _____ microfarads. - ANSWER✔✔ 50
13 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 A transformer in which the secondary voltage is in phase with the primary voltage is called a(n) _____ transformer. - ANSWER✔✔like-wound What is the voltage across the secondary winding if the primary winding has 120VAC applied to it, the primary has 200 turns, and the secondary has 300 turns?
- ANSWER✔✔180VAC An isolation transformer can help prevent electrical shocks. - ANSWER✔✔True
14 A(n) _____ is often used in fluorescent lighting circuits. - ANSWER✔✔Autotransformer If a sine wave is repeated 10 times per half second, its frequency is - ANSWER✔✔20Hz 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
16 on transformer schematic, dots are used as - ANSWER✔✔polarity A transformer has 200 turns in primary, 100 turns in secondary and 120VAC to the primary (Ep) what is Es? - ANSWER✔✔60VAC Voltage-sensing relay is likely to be powered by - ANSWER✔✔Potential Transformer
