A portable power bank stores of energy when fully charged

PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Circuits · Electric Circuits

Problem

A portable power bank stores

100\,\text{Wh}

of energy when fully charged. It is used to run simultaneously: • an LED strip that draws

0.50\,\text{A}

5.0\,\text{V}

, and • a DC fan that operates at

12\,\text{V}

and draws an unknown current

I

. The conversion efficiency of the power bank (from stored chemical energy to electrical output) is only 80 %. Both appliances are required to run together for

3.0\,\text{h}

. (i) Calculate the total electrical energy actually available to the appliances during the

3.0\,\text{h}

operation. (ii) Determine the electrical energy consumed by the LED strip in this interval. (iii) Hence find the energy that can be supplied to the fan. (iv) Using your result in part (iii), calculate the maximum current

I

that the fan may draw at

12\,\text{V}

so that the required operating time is achieved.

Related theory

Browse the problem library