# Hello, hello? My phone's almost dead...drat.

Cell phone batteries are rated by their voltage and total ability to output current, usually in units of milliamperes $$\times$$ hours, for which we use the abbreviation mA-h. If a battery has a value of $$1000~\mbox{mA-h}$$, this means it can deliver $$1000~\mbox{mA}$$ of current for one hour. The cell phone battery in this question has a voltage rating of $$3.7~\mbox{V}$$ and current rating of $$1100~\mbox{mA-h}$$. How much energy in Joules does the battery store when fully charged?

Details and assumptions

• Assume the voltage remains constant as the battery discharges. The voltage of real batteries decreases as they discharge, but we'll ignore that effect for simplicity.
• Hint: Try converting the rating to Amp-seconds and think how you could use that unit with Volts to get an energy.
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