Question

The battery of a mobile phone is rated as 4.2 V, 5800 mAh. How much energy is stored in it when fully charged?

• A. 43.8 kJ
• B. 48.7 kJ
• C. 87.7 kJ
• D. 24.4 kJ

Hint:

To calculate energy stored in a battery, use the formula \( E = Vq \), where \( V \) is the voltage and \( q \) is the charge in coulombs.

Answer 1

The Correct Option is C

Given the voltage \( V = 4.2 \) volts and the battery capacity \( 5800 \) mAh, we can calculate the energy stored in the battery using the formula: \[ \text{Energy supplied by battery} = Vq \] where \( q \) is the charge in coulombs. Converting \( 5800 \) mAh to coulombs: \[ q = 5800 \times 3600 \times 10^{-3} \, \text{C} = 5800 \times 3.6 \, \text{C} = 20880 \, \text{C} \] Thus, the energy supplied by the battery is: \[ \text{Energy} = 4.2 \times 5800 \times 3600 \times 10^{-3} = 87.696 \, \text{kJ} \] Therefore, the energy stored in the battery when fully charged is approximately \( 87.7 \, \text{kJ} \).