Circuits with capacitators
Not what you're looking for?
The figure (attached) shows a simplified circuit for a photographic flash unit. This circuit consists of a 9.0 V battery, an R = 45.0 k resistor, a 140 µF capacitor, a flashbulb, and two switches. Initially, the capacitor is uncharged and the two switches are open. To charge the unit, switch S1 is closed; to fire the flash, switch S2 (which is connected to the camera's shutter) is closed. How long does it take to charge the capacitor to 5.5 V?
(See attachment for diagram)
I do not know how to do circuits with capacitors in them. I tried treating the circuit like it was in parallel, but it didn't work. I also tried using calculus and got 5.9 x 10-3 seconds, but it was wrong.
Purchase this Solution
Solution Preview
Suppose, at any given moment of time t, the charge on the capacitor (C = 0.14x10^{-3}F) is
Q(t).
Then the voltage on the capacitor is
V_c = Q(t) / C
Given this voltage, if the switch S_1 is closed and the switch S_2 is open (the charging stage), the current is
I = (V_b-V_c) / R,
where V_b = 9 V is the voltage of the battery.
Since
I = dQ/dt,
we now have a differential equation for Q as a function of time:
...
Purchase this Solution
Free BrainMass Quizzes
Intro to the Physics Waves
Some short-answer questions involving the basic vocabulary of string, sound, and water waves.
Classical Mechanics
This quiz is designed to test and improve your knowledge on Classical Mechanics.
Introduction to Nanotechnology/Nanomaterials
This quiz is for any area of science. Test yourself to see what knowledge of nanotechnology you have. This content will also make you familiar with basic concepts of nanotechnology.
Basic Physics
This quiz will test your knowledge about basic Physics.
The Moon
Test your knowledge of moon phases and movement.