What is one cause of oscillatory transients?

Question

Options

• ALightning strikes
• BNon-unity power factors
• CMotors turning on and off
• DStatic electricity discharges

• A
  2% (1)
• B
  6% (3)
• C
  80% (39)
• D
  12% (6)

Explanation

Motors turning on and off creates oscillatory transients because switching an inductive load (like a motor) on or off causes a sudden interruption or change in current flow. The inductance of the motor and the capacitance present in the circuit then exchange energy back and forth, producing a voltage disturbance that oscillates at the circuit's natural resonant frequency before dying out.

Lightning strikes (A) and static electricity discharges (D) are both causes of impulsive transients - single, unidirectional voltage spikes - not oscillatory ones. Non-unity power factor (B) describes a condition where voltage and current are out of phase, which reduces efficiency and stresses equipment, but does not itself generate transients.

Memory tip: Oscillatory means "back and forth," just like a motor repeatedly switching on and off drives energy back and forth between inductance and capacitance in the circuit.

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