Sci-Tech

Question Corner: How does a fully charged mobile phone lose its charge when left unused?

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Readers may send their questions/answers to questioncorner@thehindu.co.in

Q: How does a fully charged mobile phone lose its charge when left unused for several days together?

A:

Kingshuk Roy

IISER, Pune

Lithium-ion battery chemistries are associated with self-discharge phenomena. A passivation layer develops on the electrodes over time (on performing several charging-discharging cycles) which results in self-discharging of the battery. It means internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. Studies show a self-discharge rate of Li-ion battery is 5% in 24 hours, then 1–2% per month. It must be borne in mind that even when the phone is kept idle, there are a lot of applications working in the background like phone-watch, calender, to name a few. These applications in-turn cause a charge loss.

Q: How does water rise up tall trees during autumn and winter when there is very less water evaporation from leaves?

A:

Senthil Subramanian

South Dakota State University, U.S.

During late autumn and winter deciduous trees are dormant. The colder temperatures during these seasons are not optimal for most physiological reactions in cells. Therefore, trees do not need a lot of water in the winter. The amount of transpiration is only one-sixth that during the peak growing season. Trees can also store water in their stems which they use during the winter. This also reduces the need for transpiration to obtain water during the winter.

This week’s question:

Are buildings with stilt parking (without a wall joining the stilts) at greater risk of collapsing during an earthquake?

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Printable version | Jan 25, 2020 12:55:53 AM | https://www.thehindu.com/sci-tech/question-corner-how-does-a-fully-charged-mobile-phone-lose-its-charge-when-left-unused/article30310428.ece

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