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SESK: Stuff Everyone Should Know · sesk.info/hamg-g5b03

How many watts does an 800-ohm load consume when it is supplied with 400 volts DC?

200 watts, since power is voltage squared divided by resistance.

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  1. 0.5 watts
  2. 200 watts ✔
  3. 3200 watts

Why: Power equals voltage squared divided by resistance. 400 squared is 160,000, and dividing by 800 gives 200 watts.

Huh, didn't know that: At 40 volts, the same load would use only 2 watts, because power rises with the square of voltage.

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Where do electricians buy their supplies? The Ohm Depot.
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References

Answer: 200 watts. Power equals voltage squared divided by resistance. 400 squared is 160,000, and dividing by 800 gives 200 watts.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    200 watts
    Checked 2026-10-11.

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Ham RadioWhat is the PEP produced by 200 volts peak-to-peak across a 50-ohm dummy load?Ham RadioA signal reads 20 dB over S9. How does its power compare with an S9 signal?Ham RadioAbout how many dB represents a factor of two increase or decrease in power?

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