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Physics · Grades 10–12

Power in a series resistor network

Ideal source and wires; resistors are ohmic and connected in series.

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Rule and assumptions

Ideal source and wires; resistors are ohmic and connected in series.

P = V²/(R₁ + R₂)

Worked examples

In a theoretical circuit, 1 Ω and 35 Ω are in series across an ideal 43 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

P = V²/(R₁ + R₂) 43² / (1 + 35) = 51.361

51.361 W

In a theoretical circuit, 36 Ω and 31 Ω are in series across an ideal 22 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

P = V²/(R₁ + R₂) 22² / (36 + 31) = 7.224

7.224 W

Try two questions

  1. In a theoretical circuit, 12 Ω and 23 Ω are in series across an ideal 5 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

  2. In a theoretical circuit, 8 Ω and 27 Ω are in series across an ideal 14 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

Answers and reasoning

Answers and marking notes
  1. 0.714 W

    P = V²/(R₁ + R₂) 5² / (12 + 23) = 0.714

  2. 5.6 W

    P = V²/(R₁ + R₂) 14² / (8 + 27) = 5.6

Further reading and review references

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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.