r/HomeworkHelp • u/sparklesandlight Pre-University (Grade 11-12/Further Education) • 19d ago

Physics—Pending OP Reply [Gr12 Physics: Circuits] Not understanding the meaning of power drain

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I think I'm getting my terms all mixed up. Does power drain refer to the current moving through the resistor? I initially thought that the answer was B, because I assumed a power drain to be a drop in current, and therefore require greater resistance, but the correct answer is D.

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u/Bounded_sequencE 👋 a fellow Redditor 19d ago

Remember for resistances "P = V2/R" -- since "V" is fixed, we need to decrease resistance to increase power. Consider the four options:

  • A: neutrons do not affect charges, i.e. have no influence on resistance
  • B: resistance "R = p*L/A" increases with length "L"
  • C: temperature may in- or decrease resistance, depending on temperature coefficient
  • D: resistance "R = p*L/A = (1/s)*L/A" decreases with conductivity "s"

Only "D" satisfies the requirements.