Practice Test Geeks(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test
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AC/DC Theory and Circuits Flashcards

6 cards from real NETA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 AC/DC Theory and Circuits flashcards as text

  1. A technician is analyzing a series AC circuit operating at 60 Hz. The circuit contains a resistor (R) of 8 ohms, an inductor with an inductive reactance (XL) of 10 ohms, and a capacitor with a capacitive reactance (XC) of 4 ohms. What is the total impedance (Z) of this circuit?

    Answer: 10.0 ohms

    The total impedance (Z) in a series RLC circuit is calculated using the formula: Z = √[R² + (XL - XC)²]. In this case, Z = √[8² + (10 - 4)²] = √[64 + 6²] = √[64 + 36] = √100 = 10.0 ohms.

  2. In an AC power system, which of the following best describes the relationship between true power (P), reactive power (Q), and apparent power (S)?

    Answer: Apparent power is the vector sum of true power and reactive power.

    The relationship between true power (measured in Watts), reactive power (measured in VAR), and apparent power (measured in VA) is represented by the power triangle. Apparent power (S) is the hypotenuse, representing the vector sum of true power (P) and reactive power (Q), expressed by the formula S² = P² + Q².

  3. A technician closes a switch to apply a DC voltage source to a circuit containing only a resistor and a large inductor in series. Immediately at the instant the switch is closed (t=0), how does the inductor behave?

    Answer: As an open circuit, with maximum voltage drop.

    Due to its property of opposing a change in current, an inductor will initially behave as an open circuit the moment a DC voltage is applied. At this instant (t=0), current has not yet begun to flow, so the current is zero, and the full source voltage is dropped across the inductor.

  4. A field service report notes that a three-phase transformer is consistently running hotter than its nameplate rating would suggest, despite the load current being within limits. Which of the following is the most likely cause for the overheating?

    Answer: High levels of harmonic distortion

    Harmonic currents, which are multiples of the fundamental frequency, can cause significant additional heating in the windings and core of a transformer due to increased eddy current and hysteresis losses. This leads to overheating even when the fundamental load current is not excessive.

  5. A technician uses a power quality analyzer on an AC circuit and measures the true power as 4.0 kW and the apparent power as 5.0 kVA. What is the power factor of this circuit?

    Answer: 0.80

    Power factor (PF) is defined as the ratio of true power (P) to apparent power (S). The formula is PF = P / S. In this scenario, PF = 4.0 kW / 5.0 kVA = 0.80.

  6. According to Kirchhoff's Current Law (KCL), what is the current (I_total) entering a junction if three branches leaving the junction have currents of 2 A, 5 A, and 3.5 A?

    Answer: 10.5 A

    Kirchhoff's Current Law (KCL) states that the algebraic sum of currents entering a node (or junction) must equal the sum of currents leaving that node. Therefore, I_total = 2 A + 5 A + 3.5 A = 10.5 A.