Question

If you wish to take a picture of a bullet traveling at 500 m/s, then a very brief flash of light produced by an RC discharge through a flash tube can limit blurring. Assuming 1.00 mm of motion during one RC constant is acceptable, and given that the flash is driven by a 600-μF capacitor, what is the resistance in the flash tube?

Answer 1

Explanation:

The given data is as follows.

       Speed of the bullet (v) = 500 m/s

     Distance during one RC time constant (d) = 1 mm = $1 \times 10^{-3} m$

      Capacitance (C) = 600 $\mu F$ = $600 \times 10^{-6} F$

Hence, formula for speed of the bullet is as follows.

                v = $\frac{d}{t}$

or,           t = $\frac{d}{v}$

Time constant for RC circuit is as follows.

          t = RC

        R = $\frac{t}{C}$

            = $\frac{d}{vC}$

            = $\frac{1 \times 10^{-3}}{500 \times 600 \times 10^{-6}}$

            = $3.33 \times 10^{-3} ohm$

Thus, we can conclude that resistance in the flash tube is $3.33 \times 10^{-3} ohm$.