alleryStart learning →A 10 ohm resistor is connected in parallel with a second resistor R, giving a combined equivalent resistance of 8 ohm. What is the value of R?
A20 ohm
B2 ohm
C80 ohm
D40 ohm
Answer & Solution
Correct answer: D. 40 ohm
1. For two resistors in parallel: 1/R_equiv = 1/R1 + 1/R2.
2. Substitute R_equiv = 8 ohm and R1 = 10 ohm: 1/8 = 1/10 + 1/R.
3. Solve for 1/R: 1/R = 1/8 - 1/10 = 1/40.
4. R = 40 ohm.
_Source: OpenStax Physics (CC BY 4.0), Ch 19 "Electrical Circuits", section 19.3 Parallel Circuits_
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