A mobile phone requires 5.0 V at its input and draws 1.8 A during fast charging
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Circuits · Electric Circuits
Problem
A mobile phone requires 5.0 V at its input and draws 1.8 A during fast charging. It is connected to a 5.0 V USB adapter through a cable whose conductors have some resistance.
(i) When the charging current is 1.8 A, the adapter has to supply 5.4 V so that 5.0 V appears at the phone end. Calculate the total resistance of the cable.
(ii) The same cable is used with another phone that draws only 1.0 A. Determine the voltage that will now appear at the phone end.
(iii) For efficient charging, the voltage at the phone must not fall below 4.9 V. Find the maximum current that can be drawn through this cable without violating this condition.