7/17/2019 Physics2A_CheatSheet

http://slidepdf.com/reader/full/physics2acheatsheet 1/1

 

V

 

SWITCH IN CAPACITOR

When there is a switch to

disconnect from voltage

source:

Q(int) = C*V

 

WHE C!"C#"!$%& E '%E" WHE r >

radius of sphere use radius of shere

for volume and r for

 + * * r,-

 

 E.uation is for oint charge

#%$S (/C)

Electric 0eld follows

suerosition

Electric 0eld is 1ased o2

directionr = distance to the electric 0eld

 (%n0nite line of charge)

 (%n0nite Sheet) umerator =

#niform Charge ensit3 = = Q/Volume

Surface = sigma = Q/!rea

"inear = lam1da = Q/d (C/m)

4,- is distance 1etween two

charges

Forces are equal and opposite

'orce is 1ased on direction

(down and left is negative)

= .d (diole moment

charge times distance

searated)

 $or.ue = Esin(5)

 $or.ue Vector = (cross

rod) E

# = 6 (dot rod) E

7 = 8 *

#%$S (*m,- / C)

!mount of electric 0eld 9ow

through a surface

'low ointing inwards =

negative

'low ointing outwards =

ositive

ero 9u; when:

  No charge inside surface, zero

netcharge inside surface, parallel to

surface, inward ux cancels

outward ux 

E erendicular to !rea

times !rea

E arallel to !rea vector

times !rea

!ngle is 1etween E and !

vector

  <ottom e.uation wor7s

onl3 for s3mmetrical

sherical surface

  ro1lem from HW

 %f more

than one

ointElectric otential is the

negative derivative of

Electric 0eld

'or an electron

moving in direction of 

E 0eld:

E increases from

high to low otential

E increases as >E

decreases

>E decreases in

direction of E 0eld

W =

6.Ed. in formula a1ove is test

charge

E = #

'orce = negative

derivative of #

  #nits (')1 = radius of outer

conductor

a = radius of inner

conductor

 

HA$F FI$$%&

CAPACITORUse parallel-plate

capacitance but add (k+1)

and diide b "

When solving series/arallel solve the arallel 0rst

and solve the whole s3stem as a series@

!lso for two in series 3ou can use Ce2 = (C?*C-) /

(C?AC-)

Bore than two: (C?*C-*C) / (C?*C- A C?*C A

C-*C)

Series have same charge

 

 

tot surface charge on int

surface of the conductor (wall

of cavit3) = 6.

tot surface charge on e;t

surface of the conductor

(3ellow 1all) = .

E(int) = 7./r,-

E(e;t) = the same as the 0eld

roduced 13 the oint charge

. located at the center of the

shere

WH%N q' IS (RO)*HT

O)TSI&% CON&)CTOR+

.(int) would not change

.(e;t) would not change

E(;) = 6!3 A -<;

E(3) = 6!; D C

E() = F

When E = F:

E(;) = (6C/!) E(3) = (6

-<C)/(!,-)

E() = C/!

 inner , a - c , .'q

Outer , / - d , #'q

r G a E? = F

a G r G 1 E- = F

1 G r G c E = (7-.) / r,-

direction is outward the

center

c G r G d E = F

r I d EJ = F

 $otal charge on inner surface

of small shell = F

 $otal charge on the outer

surface of small shell = -.

 $otal charge on inner surface

of large shell = 6-. $otal charge on outer surface

of small shell = F

Coulom1Ks "aw D Electric