Question

A smart phone charger delivers charge to the phone, in the form of electrons, at a rate of$-0.75\mathrm{C}/\mathrm{s}$ . How many electrons are delivered to the phone during $30\min$ of charging?

Short answer

Delivered electrons are$8.4\times {10}^{21}\mathrm{electrons}$.

Step-by-step solution

Calculation for charge

Charge is,

$\mathrm{Q}=\mathrm{N}\mathrm{e}$

Where $\mathrm{e}=-1.6\times {10}^{-19}\mathrm{C}$.

So,

$\mathrm{N}=\frac{\mathrm{Q}}{\mathrm{e}}$

The rate of accumulation of the electrons is ,

$\frac{\mathrm{Q}}{\mathrm{t}}$

$=-0.75\mathrm{C}/\mathrm{s}$

For time $\mathrm{t}=30\min$,

Where,

$\mathrm{t}=30\min =30\left(60\mathrm{s}\right)$

$=1800\mathrm{s}$

So,

$\mathrm{Q}=(-0.75\mathrm{C}/\mathrm{s})\mathrm{t}$

$=(-0.75\mathrm{C}/\mathrm{s})(1800\mathrm{s})$

$=-1350\mathrm{C}$

Calculation of electrons

Electron is,

$\mathrm{N}=\frac{\mathrm{Q}}{\mathrm{e}}$

$=\frac{-1350\mathrm{C}}{-1.6\times {10}^{-19}\mathrm{C}}$

$=8.4\times {10}^{21}\mathrm{electrons}$