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Simple Physics Problem?
A total resistance of 3.05 Ω is to be produced by connecting an unknown resistance to a 12.19 Ω resistance. (a) What must be the value of the unknown resistance, and (b) should it be connected in series or in parallel?
1 Answer
- 5 years ago
To answer part (b) first.
The general rule is that for resistors in series, the equivalent resistance is always bigger than the biggest individual resistor.
For resistors in parallel, the equivalent resistance is always smaller than the smallest individual resistor.
So if you want the equivalent resistor to be only 3.05 Ω the unknown resistance Rx) must be in parallel with the 12.19 Ω resistor.
1 / 3.05 = 1 / 12.19 + 1/Rx
1/Rx = 1/3.05 - 1/12.19 = 0.2458
Rx = 1/0.2458 = 4.07 Ω {To 3 significant figures}
