   Chapter 18, Problem 36P

Chapter
Section
Textbook 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 flash bulb if the capacitor discharges 90.0% of its full charge in 1.00 ms.

(a)

To determine
The resistance R if the capacitor charges to 90.0% of its final value in 15.0s .

Explanation

Given Info: Capacitance C is 125μF , time t is 15.0s charge on the capacitor q is 90.0% maximum charge on the capacitor Q is 100.0%

Explanation:

Formula to calculate the time constant τ of the circuit

q=Q(1e(tτ))

On rearrange

τ=tln(1qQ)

• C is the capacitance of the capacitor,
• τ is the time constant,
• t is the time
• q is the charge on the capacitor,
• Q is the maximum charge on the capacitor,

Substitute, 15.0s for t , 90.0% for q and 100.0% for Q in the above equation to find τ

τ=15.0sln(190.0%100.0%)=15

(b)

To determine
The average current Iav delivered to the flash bulb if the capacitor discharges 90.0% of its full charge in 1.00ms .

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started

Find more solutions based on key concepts 