Q 12-03-300JEE MainJEE Main 2025 (2 Apr, Shift 1)Easy
The battery of a mobile phone is rated as $4.2\ \text{V}$, $5800\ \text{mAh}$. How much energy is stored in it when fully charged?
Answer: (C) $87.7\ \text{kJ}$
Charge stored: $Q = 5800\ \text{mAh} = 5.8\ \text{A} \times 3600\ \text{s} = 20880\ \text{C}$.
Energy $= VQ = 4.2 \times 20880 = 87696\ \text{J} \approx 87.7\ \text{kJ}$.
Solution by Sreeraj P, M.Sc Physics