Physics Toolbox: Circuits

testybelchMechanics

Nov 14, 2013 (3 years and 8 months ago)

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Physics Toolbox:
Circuits


These equations
will

be given on the exam

because they are less fundamental than others
:



2
2
( )
( )
dU V
P I R I V
dt R

    


2
2
1 1
( ) ( )
2 2 2
Q
U C V Q V
C
    


L L
R
A A


 




E
J E


 






These equations
will not

be given on the exam because they contain foundational concepts that we
want you to remember after the semester ends:



dq
I
dt



I
J
A



V
I
R




Q
C
V




1
1
series
1 1
parallel
N
eq i
i
N
i
eq i
R R
R R








1
1
parallel
1 1
series
N
eq i
i
N
i
eq i
C C
C C










1
Loop rule: 0
Junction rule:
N
loop
i
i
in out
V V
I I

   


 



K
now how to derive these equations for current, voltage, and charge as a function of time for
discharging
and
charging capacitors.

(You might want to just memorize the
m
, too.)


Discharging:



Charging:

0
( )
t RC
I t I e





0
( )
t RC
I t I e



0
( )
t RC
V t V e







max
( ) 1
t RC
V t V e

 

0
( )
t RC
Q t Q e






max
( ) 1
t RC
Q t Q e

 


Time constant =
RC