Question

The duration of a photographic flash is related to an RC time constant, which is 0.200 µs for a certain camera. (a) If the resistance of the flash lamp is 0.0410 Ω during discharge, what is the size (in µF) of the capacitor supplying its energy? µF (b) What is the time constant (in s) for charging the capacitor, if the charging resistance is 650 kΩ? s

Answer 1

Explanation:

It is given that,

The time constant of RC circuit, $\tau=0.2\ \mu s=0.2\times 10^{-6}\ s$

(a) The resistance of the flash lamp is 0.0410 Ω

We know that the relation between the resistance and time constant is given by :

$\tau=R\times C$

$C=\dfrac{\tau}{R}$

$C=\dfrac{0.2\times 10^{-6}}{0.0410}$

$C=4.87\times 10^{-6}\ F$

(b) If he value of resistance, $R=650\ k\Omega=650\times 10^3\ \Omega$

$\tau=R\times C$

$\tau=650\times 10^3\times 4.87\times 10^{-6}$

$\tau=3.16\ s$

Hence, this is the required solution.