If AP power level is increased from 25 mW to 100 mW. What is the power difference in dBm?

Question

Options

• A6 dBm
• B14 dBm
• C17 dBm
• D20 dBm

• A
  79% (26)
• B
  6% (2)
• C
  12% (4)
• D
  3% (1)

Explanation

Explanation

Option A (6 dBm) is correct because the power increased 4x (from 25 mW to 100 mW), and in decibel math, every doubling of power = +3 dB; since 4x = two doublings, that equals 3 dB + 3 dB = 6 dBm. Option B (14 dBm) is incorrect and likely results from confusing this with an absolute dBm conversion rather than a difference calculation. Option C (17 dBm) is the absolute dBm value of 50 mW, not the difference between the two power levels. Option D (20 dBm) is the absolute dBm value of 100 mW itself, not the change in power - a common trap when students forget the question asks for the difference.

Memory Tip: Use the "Rule of 3s and 10s" - every time power doubles, add 3 dB; every time power increases 10x, add 10 dB. Here, 25→50→100 mW is two doublings, so 3+3 = 6 dBm.

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