alleryStart learning →A 45 ohm resistor and a 60 ohm resistor are wired in parallel with each other. What is their combined resistance?
A105 ohm
B52.5 ohm
C15 ohm
D25.7 ohm
Answer & Solution
Correct answer: D. 25.7 ohm
1. For two resistors in parallel: 1/R_equiv = 1/45 ohm + 1/60 ohm.
2. 1/45 ohm + 1/60 ohm = 4/180 ohm + 3/180 ohm = 7/180 per ohm.
3. R_equiv = 180/7 ohm, which is approximately 25.7 ohm.
4. 105 ohm and 52.5 ohm both come from adding or averaging the two resistances, which is the series rule, not the parallel rule.
_Source: OpenStax Physics (CC BY 4.0), Ch 19 "Electrical Circuits", section Find the Current through a Complex Resistor Circuit_
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