Question 131: Current Electricity

Question

The battery of a mobile phone is rated as $4.2 \mathrm{~V}, 5800 \mathrm{~mAh}$. How much energy is stored ir it when fully charged?

Accepted Answer

To find the energy stored in the battery, follow these steps:
Convert mAh to Ah:
The battery capacity is given as 5800 mAh. Since
$$1\,	ext{Ah} = 1000\,	ext{mAh},$$
we have
$$5800\,	ext{mAh} = 5.8\,	ext{Ah}.$$
Calculate energy in watt-hours (Wh):
The energy in Wh is given by the product of the voltage and the capacity in Ah. Thus,
$$	ext{Energy (Wh)} = 4.2\,	ext{V} 	imes 5.8\,	ext{Ah} = 24.36\,	ext{Wh}.$$
Convert watt-hours to joules (J):
Since
$$1\,	ext{Wh} = 3600\,	ext{J},$$
the total energy in joules is:
$$24.36\,	ext{Wh} 	imes 3600\,	ext{J/Wh} = 87,696\,	ext{J} \approx 87.7\,	ext{kJ}.$$
Thus, the energy stored in the battery when fully charged is about 87.7 kJ.
The correct answer is Option A: 87.7 kJ.

Answer

87.7 kJ

Answer

43.8 kJ

Answer

48.7 kJ

Answer

24.4 kJ

Current Electricity

The battery of a mobile phone is rated as 4.2 \mathrm{~V}, 5800 \mathrm{~mAh}. How much energy is stored ir it when fully charged?

Choose the correct answer: