A mobile phone operates at a constant power of 200 mW It has a 3.7 V lithium-ion battery that has a charge capacity of 9400 C What is the time taken for the battery to discharge completely? - AQA - A-Level Physics - Question 26 - 2018 - Paper 1

The time (t) taken to discharge the battery can be calculated using the formula:

$t = \frac{E}{P}$

where:

• $E$ is the energy (34680 J)
• $P$ is the power (200 mW or 0.2 W)

Now substituting the values:

$t = \frac{34680 ext{ J}}{0.2 ext{ W}} = 173400 ext{ seconds}$

To convert seconds into hours:

$173400 ext{ seconds} \div 3600 \approx 48.25 ext{ hours}$

Thus, the time taken for the battery to discharge completely is approximately 48 hours.

Based on the calculation, the correct option is B. 48 hours.