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The CETa exam has 100 questions and runs 2 hours.
These 10 free CETa questions are organized by exam domain, so you can see how each part of the Associate Certified Electronics Technician blueprint is tested. Reveal the answer and explanation under each question.
During power-supply servicing, a qualified technician isolates and locks out the incoming source. The input terminals test deenergized, but a correctly rated meter still measures 168 V across the bulk capacitor. The power indicator is dark. Before measuring the bleeder resistor with an ohmmeter, the technician must:
Correct answer: B - Follow the approved discharge procedure, then verify absence of voltage.
A PWM controller applies either 24 V or 0 V directly across a 24 Ω resistive heater. The waveform is HIGH for 25% of each cycle. Assume constant heater resistance and negligible switching losses. What average power does the heater dissipate?
Correct answer: A - 6.0 W
Q1 is an NPN transistor switching a 12 V relay coil, with its emitter connected to return. With the relay commanded ON, the base measures 0.78 V and the collector 0.16 V relative to the emitter. With the command OFF, these readings become 0 V and 12 V, and the relay releases. How should Q1's operation be classified?
Correct answer: D - Normal switching: saturation when ON and cutoff when OFF.
A sine-wave source with constant RMS voltage drives a series circuit containing an ideal inductor, an ideal capacitor, and a fixed nonzero resistance. The frequency is adjusted until the inductor and capacitor voltages are equal in magnitude and opposite in phase. At this operating point, which description is correct?
Correct answer: A - Minimum input impedance; current in phase with the source voltage.
Several joints on a lead-free assembly have a uniform matte finish. Magnified inspection shows proper wetting, continuous fillets, and no cracks, bridges, or loose leads. The joints pass the specified electrical and workmanship checks; no special cosmetic finish is required. Which disposition is justified?
Correct answer: B - Leave the joints intact; matte appearance alone does not justify rework.
An Ethernet patch cord passes a basic continuity test: every contact connects to the same numbered contact at the other end, with no shorts. Inspection shows that its four physical twisted pairs occupy contacts 1-2, 3-4, 5-6, and 7-8 at both connectors. What termination defect has the continuity test missed?
Correct answer: C - Split pairs at contacts 3-6 and 4-5.
A 12.0 V source feeds two 1.0 MΩ resistors in series. In separate measurements, a voltmeter with 1.0 MΩ input resistance reads 4.0 V from their midpoint to return; a second meter with 10 MΩ input resistance reads 5.7 V at the same points. The source remains at 12.0 V during both measurements, and both meters pass their calibration checks. What accounts for this difference?
Correct answer: B - Each meter loads the divider through its finite input resistance.
An isolated 60 Hz transformer feeds a four-diode bridge and a reservoir capacitor. Under the same load, the output has developed greater ripple and a lower average voltage. The capacitor now receives charging pulses at 60 Hz rather than the previous 120 Hz; the transformer secondary waveform is unchanged. Which single fault best explains the change in charging frequency?
Correct answer: C - One bridge diode has failed open.
An inverting op-amp stage has a 10 kΩ input resistor, a 47 kΩ feedback resistor, and its noninverting input grounded. The amplifier uses ±12 V supplies but is specified for linear output only between −10 V and +10 V with this load. A +2.50 V DC input is applied. Input common-mode limits are satisfied. Using ideal closed-loop gain until an output limit is reached, predict the response.
Correct answer: D - Negative clipping; linear gain would require −11.75 V.
A driver guarantees a HIGH output of at least 2.4 V and a LOW output of at most 0.4 V under the connected load. Its receiver is an SN74HC00 powered at 4.5 V, requiring at least 3.15 V for a guaranteed HIGH and at most 1.35 V for a guaranteed LOW. A prototype works with a measured HIGH of 3.6 V. Based on these voltage specifications, what can be concluded about the direct connection?
Correct answer: A - The HIGH level is not guaranteed to meet the receiver's requirement.
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