Circuit Design & Troubleshooting Flashcards

A technician measures 0V across a load resistor in a series circuit. What is the most likely fault?

Answer: There is an open circuit upstream of the load

An open circuit upstream prevents current flow, resulting in 0V across the load (all voltage drops at the open point).

Which filter topology uses an inductor in series and a capacitor in parallel to pass low frequencies?

Answer: Low-pass LC filter

A low-pass LC filter places the inductor in series (blocks high frequencies) and the capacitor in shunt (bypasses remaining high frequencies to ground).

When troubleshooting a circuit with an oscilloscope, you observe a waveform with excessive ripple at the output of a rectifier. What component is most likely faulty?

Answer: The filter capacitor

A deteriorated or open filter capacitor cannot smooth the rectified waveform, causing excessive ripple voltage.

What is the purpose of a snubber circuit placed across a relay coil?

Answer: To suppress voltage spikes caused by inductive kickback

When a relay coil de-energizes, its inductance produces a large reverse voltage spike; a snubber (RC or diode) clamps this transient.

In a voltage divider circuit with R1=10kΩ and R2=10kΩ connected to 24V, what is the output voltage taken across R2?

Answer: 12V

Equal resistors split the voltage equally: Vout = 24V × (10k/(10k+10k)) = 12V.

A technician finds that a PCB trace is intermittently open at a solder joint. Which troubleshooting technique is most effective for isolating this fault?

Answer: Flexing the board while monitoring continuity

Physically flexing the board stresses intermittent solder joint cracks, causing them to open and close, revealing the fault location.

Which of the following best describes a Thevenin equivalent circuit?

Answer: A voltage source in series with a resistance

Thevenin's theorem states any linear network can be reduced to a single voltage source (Vth) in series with a single resistance (Rth).