Question

The battery capacity of a lithium ion battery in a digital music player is 750 mA-h. The manufacturer claims that the player can operate for eight hours if the battery is initially fully charged. Given this information, determine the number of electrons that flow through the player as you listen to your favorite songs for three hours.
A. 6.2 times 10^18 electrons
B. 1.0 times 10^3 electrons
C. 2.4 times 10^9 electrons
D. 6.3 times 10^21 electrons
E. 8.1 times 10^28 electrons

Answer 1

Answer:

The number of electrons is $6.3\times10^{21}\ electrons$

(D) is correct option.

Explanation:

Given that,

Battery capacity = 750 mA-h

Time t= 8 hours

Time t'=3 hours

We need to calculate the battery capacity

$Battery\ capacity=750\times10^{-3}\times3600$

$Battery\ capacity=2700\ A-s$

We need to calculate the number of electrons in 1 C Li

Using formula for number of electron

$n=\dfrac{1}{e}$

$n=\dfrac{1}{1.6\times10^{-19}}$

$n=6.25\times10^{18}\ electrons$

We need to calculate the number of electron in 2700 C

$2700\ C=2700\times6.25\times10^{18}=1.68\times10^{22}\ electrons$

The total number of electrons battery can deliver in 8 hours

$n=1.68\times10^{22}\ electrons$

We need to calculate the number of electron in 3 hours

Using formula of number of electrons

$n=\dfrac{n\times t'}{t}$

Put the value into the formula

$n=\dfrac{1.68\times10^{22}\times3}{8}$

$n=6.3\times10^{21}\ electrons$

Hence, The number of electrons is $6.3\times10^{21}\ electrons$

Answer 2

Answer:

option (D)

Explanation:

capacity, q = 750 mA - h = 0.750 x 3600  A-s = 2700 C

time, t = 3 hours = 3 x 3600 seconds = 10800 s

1 C = 6.24 x 10^18 electrons

So, 2700 C = 2700 x 6.24 x 10^18 electrons

                   = 1.684 x 10^22 electrons

but it is used for 3/8 th part

so, number of electrons = 3/8 x 1.684 x 10^22

                                        = 6.315 x 10^21 electrons