AP Physics 2: 1.4 Changes and Conservation Laws

AP Physics 2: 1.4 Changes and Conservation Laws. Find the capacitance of the capacitor. 

APAP Physics 2
AP Physics 2Changes and Conservation Laws
LanguageEnglish Language
Test PrepAP Physics 2

Transcript

00:24

battery on his camera phone is dead he rushes up to the attic finds an old

00:28

flashbulb camera and makes it back down just in time to snap a photo of the [Chris using flashbulb camera]

00:32

Admiral the energy used to produce the flash is stored in a capacitor the flash

00:36

pulse has the power of 100 thousand watts and a duration of .001

00:39

seconds and the potential difference be across the capacitor plates is held

00:43

constant at 200 volts, energy is stored in a capacitor with a capacitance of C at a [physics formula]

00:48

potential difference V determine the capacitance of the capacitor assume all

00:53

the energy stored in the capacitor is converted into energy for the flash and

00:57

here are the potential answers..different kind of flash... All right, [potential answers and the Flash appears]

01:02

look not to sound jaded but we've seen all the pictures of cats playing the

01:06

piano the internet is built on piano playing cat pics is any image search [internet page of cats playing piano]

01:10

will prove sorry Chris but without video evidence of the Admiral playing

01:14

Beethoven's ninth were not impressed but a flashbulb camera that we are impressed [Chris takes picture of girl with flashbulb camera]

01:19

with it's like a historical artifact from a simpler time okay, enough about

01:23

cats and cameras.. in order to solve this problem we first need to find out how [two hands with sparks in between]

01:27

much power we're dealing with. Since all the energy in the capacitor is used by

01:31

the flash if we can figure out how much energy is needed to blind poor Admiral [Admiral being photographed by Chris]

01:35

Snugglesworth then we can figure out the total energy we're dealing with well

01:40

energy equals power times time in this case we have a hundred thousand watts of [Energy formula shown on blackboard]

01:44

power used in one, one thousandth of a second and that means the total energy

01:49

is a hundred joules we were already given the equation to calculate the

01:53

stored energy we just need to arrange that equation to find the capacitance [equation for stored energy rearranged]

01:57

starting with the equation U sub E equals one half CV squared we find that

02:02

C equals 2U sub E over V squared plugging in the numbers we find that the

02:08

capacitance equals five microfarads which means the correct answer is D

02:13

if we ever have a pet talented enough to actually play an instrument we're going [Admiral playing the piano and jumps on Chris]

02:17

to be very careful taking pictures the last thing we want from her is to get

02:21

camera shy because we finally get the paparazzi's attention we've always [paparazzi taking snaps of Admiral and Chris]

02:25

wanted.