Red Seal Electrician Practice
Meters and troubleshootingQuestion 656 of 1506

What is the best way to work out what a circuit will do after a component fails?

  1. Redraw it with the resistance of the failed part and recalculate.
  2. Replace every other part in the circuit before you start.
  3. Raise the supply voltage until the circuit works again.
  4. Assume that all branch currents stay as they were before.
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Correct answer: Redraw it with the resistance of the failed part and recalculate.

A short is a very low resistance and an open is a very high one. Put that value in and solve the circuit again.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 5.7: Component Failure Analysis

Practice meters and troubleshooting

Questions last reviewed: 18 October 2026