Question

In a particular television tube, a beam of electrons has a current of 5.8 × 10−5 A . How long does it take for 1.17 × 1015 elec- trons to strike the screen? The fundamental charge is 1.602 × 10−19 C . Answer in units of s.

Answer 1

Here we know that current is defined as rate of flow of charge

so here we have

$i = \frac{dQ}{dt}$

here we also know that

Q = Ne

now we have

$i = \frac{Ne}{t}$

now in order to find time we have

$t = \frac{Ne}{i}$

here we know that

$N = 1.17 \times 10^{15}$

$e = 1.602 \times 10^{-19}C$

$i = 5.8 \times 10^{-5}A$

now we have

$t = \frac{1.17\times 10^{15} (1.602 \times 10^{-19}}{5.8 \times 10^{-5}}$

$t = 3.23 s$