Answer 6—Separate the eight resistors into two groups of four and take the series resistance of one of these groups. If the total resistance is 4 kW, the odd resistor is in the other pile. If the resistance is not 4 kW, the odd resistor is in this pile. Call the bad pile "A" and the good pile "B."

Next, connect three of the resistors from pile A in series. Connect three resistors from pile B in parallel with the first A resistor, and connect one resistor from pile B in parallel with the second A resistor. Refer to the following diagram:

Measure the total resistance of this network. The ohmmeter will give different readings depending on whether the odd resistor is in column 1, 2, 3, or is the one not used.

 

Bad resistor	Resistance reading
A0	1750 W
A1 shorted	1500 W
A1 open	1833 W
A2 shorted	1250 W
A2 open	2250 W
A3 shorted	750 W
A3 open	Open circuit

Contributor: Eddie Insam

Published November 2003