alleryStart learning →Three 10 ohm resistors are connected in parallel across a 9.0 V battery. What power is dissipated in the circuit?
A2.7 W
B90 W
C8.1 W
D24 W
Answer & Solution
Correct answer: D. 24 W
1. For three identical 10 ohm resistors in parallel, the equivalent resistance is R divided by 3: R_equiv = 10 ohm / 3, about 3.33 ohm.
2. Use P = V^2 / R_equiv.
3. P = (9.0 V)^2 / 3.33 ohm = 81 / 3.33 W.
4. P is approximately 24 W.
5. 2.7 W is the power for the same three resistors connected in series instead of parallel, a much higher resistance combination that draws far less power.
_Source: OpenStax Physics (CC BY 4.0), Ch 19 "Electrical Circuits", section 19.4 Electric Power_
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