Under 802.3af, why does the powered device receive less power than the PSE's maximum?

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Multiple Choice

Under 802.3af, why does the powered device receive less power than the PSE's maximum?

The key idea is that power in PoE isn’t delivered at the PSE’s maximum value because the copper path between the PSE and the PD wastes some of that power. The PSE can source up to 15.4 W, but the resistance of cabling and connectors causes a voltage drop as current flows to the PD. That drop reduces the actual power reaching the PD, so the device ends up with less power than the PSE maximum. PoE does use detection and classification to determine how much power a PD can safely draw, and the PD will pull only what it needs, but the line losses are the main reason for the lower delivered power. The other options describe faults or misconceptions about PoE operation, not the normal cause of power being lower than the PSE’s maximum.

The key idea is that power in PoE isn’t delivered at the PSE’s maximum value because the copper path between the PSE and the PD wastes some of that power. The PSE can source up to 15.4 W, but the resistance of cabling and connectors causes a voltage drop as current flows to the PD. That drop reduces the actual power reaching the PD, so the device ends up with less power than the PSE maximum. PoE does use detection and classification to determine how much power a PD can safely draw, and the PD will pull only what it needs, but the line losses are the main reason for the lower delivered power. The other options describe faults or misconceptions about PoE operation, not the normal cause of power being lower than the PSE’s maximum.

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