The RC charging circuit in a camera flash unit has a voltage source of 275 V and a capacitance of 125 µF.

PROBLEM:

The RC charging circuit in a camera flash unit has a voltage source of 275 V and a capacitance of 125 µF.

a). Find its resistance R if the capacitor charges to 90.0% of its final value in 15.0 s.

b). Find the average current delivered to the flashbulb if the capacitor discharges 90.0% of its full charge in 1.04 ms.

STRATEGY:

To solve this RC (Resistor-Capacitor) circuit problems involving charging or discharging, start by recalling the exponential formulas for voltage and charge in RC circuits. For part (a), make T the subject of the formular and then calculate what is 90% of 100%. (b) Calculate the resistance by substituting given values in the equation T = RC and then Calculate for average current delivered.

DATA COLLECTION:

1. V = 275V

2. C = 125µF.

3. t = 15.0s

4. Q = 90.0%

SOLUTIONS: 

(a).

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(b).

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