basic electric theory (series circuit)

Thread Starter


Joined Oct 30, 2011
Need help,this is one of 5 questions that I need help with.A circuit. Contains 8 incandescent lamps connected in series across 480v.One lamp has burned out and you must determine which one is defective. You have available. A voltmeter, ammeter, and ohmmeter. Which meter would you use to determine which lamp is defective in the shortest possible time? Explain how you would use this meter and why.
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Joined Jul 9, 2011
Draw the circuit then ask yourself the following questions:

1. Is there a current flow in a circuit with 8 resistors in series where of them is interrupted?
2. Would you use an Ohmmeter in an energized circuit?
3. What's the resistance of a burnt light bulb (in relationship to the intact ones)?


Joined Feb 12, 2009
3 tests maximum. Use voltmeter if still connected to the supply. Ohmmeter if not.

A similar technique is used in Analog to Digital converters called Successive Approximation. Also called a Binary Search.

OK: if you had 16 lamps in series with one blown - how many tests then?