A disposable camera uses a circuit to charge a capacitor before triggering the flash

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A disposable camera uses a circuit to charge a capacitor before triggering the flash. The capacitor has a value of

C=2.20\,\text{mF}

and is charged from a

5.0\,\text{V}

battery through a resistor of unknown resistance

R

. The manufacturer specifies that the capacitor should reach about

63\%

of its final charge

4.0\,\text{s}

after the shutter button is pressed. Answer the following in the spaces provided. (a) Calculate the resistance

R

required to meet the manufacturer’s specification. Show your work and include appropriate units. (b) The production team considers replacing the capacitor with one of

1.10\,\text{mF}

while keeping the same resistor. Determine the new time it would take the capacitor to reach

63\%

of its final charge. (c) To shorten the recharge interval to

1.0\,\text{s}

while keeping the original

2.20\,\text{mF}

capacitor, determine the resistance that should be used.

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