Compute resistor power: When 8 mA flows through a 12 kΩ resistor, what is the resulting power dissipation?

Difficulty: Easy

Correct Answer: 768 mW

Explanation:


Introduction / Context:
Translating current through a known resistance into power helps ensure components operate within safe limits. This is commonly needed when verifying resistor wattage in bias networks and load resistors.


Given Data / Assumptions:

  • I = 8 mA = 0.008 A.
  • R = 12 kΩ = 12,000 Ω.
  • DC or RMS values implied; use standard power formulas.


Concept / Approach:
Use P = I^2 * R. Alternatively, compute voltage first via V = I * R and then apply P = V * I. Both yield the same result when done consistently in SI units.


Step-by-Step Solution:

Compute P = I^2 * R = (0.008)^2 * 12,000.(0.008)^2 = 0.000064; multiply: 0.000064 * 12,000 = 0.768 W.Convert to milliwatts: 0.768 W = 768 mW.


Verification / Alternative check:
Find V: V = I * R = 0.008 * 12,000 = 96 V. Then P = V * I = 96 * 0.008 = 0.768 W. Both methods agree.


Why Other Options Are Wrong:

  • 7.68 mW: Off by a factor of 100; likely from moving the decimal incorrectly.
  • 7.68 W and 76.8 W: Too large; would require far higher current or resistance.


Common Pitfalls:

  • Forgetting to convert kΩ to Ω and mA to A before substituting.
  • Dropping zeros when squaring the current.


Final Answer:
768 mW

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