A mobile phone battery is connected to a constant potential difference of $5.0\,\text{V}$ for charging. Over a time of $1.0\,\text{hour}$, the initial current of $0.50\,\text{A}$ gradually falls to zero, as shown. What is the best estimate of the energy transferred to the battery during the $2.0\,\text{hours}$ represented on the graph?
- A$2700\,\text{J}$
- B$9000\,\text{J}$
- C$14\,000\,\text{J}$
- D$18\,000\,\text{J}$