Exercise EE1-03.R1

Prof. Dr. Thorsten Jungmann (last updated 2025-12-07)

Relates to EE1-03 Sources

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Task

A portable LED torch is powered by an AA alkaline battery. The battery has a rated voltage of $U_0=1.5\mathrm{V}$ and a battery capacity of $Q=2500\mathrm{mAh}$.

In operation, the electric circuit of the light emitting diode draws a constant current of $I=200\mathrm{mA}$.

a) In theory, how long can the torch be operated before the battery is exhausted?

b) What energy (in joules and watt-hours) is stored in the battery?

c) What power does the electric circuit of the light emitting diode draw?

Solution

a) $t=12.5\mathrm{h}$
b) $W=13500\mathrm{J}=3.75\mathrm{Wh}$
c) $P=0.3\mathrm{W}$

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