A portable power bank stores a total of of usable energy before it must be recharged
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A portable power bank stores a total of 54kJ of usable energy before it must be recharged. Three different electronic devices can be powered by the bank, each operating at a constant power rating.
Device information (continuous operation)
• Device A: 2.0W
• Device B: 5.0W
• Device C: 9.0W
Assume the power bank delivers energy at the listed rates with no additional losses.
(a) Describe the relationship among energy transferred, operating time, and power for any device that runs at a constant power.
(b) Without performing detailed numerical calculations, rank the three devices from longest to shortest possible operating time when powered by the bank. Justify your ranking qualitatively using the data provided.
(c) Explain, without explicit calculation, how the operating time of Device C compares to that of Device A. Support your explanation with proportional reasoning based on the given power values.