your name

advertisement
LECTURE 16
Hand
Hand in
in your
your homework
homework after
after
class:
class: Print
Print both
both
•• your
your name
name
•• your
your TA’s
TA’s name
name
on
on your
your assignment,
assignment, and
and place
place
itit in
in the
the appropriate
appropriate box
box
DEMO: all bulbs are identical
4
1
3
E
2
5
6
Prediction
Prediction#1:
#1:Bulbs
Bulbs11&&22 are
areconnected
connectedfirst.
first.IfIf
bulb
bulb33isisconnected
connectednext,
next,then
then
1.)
bulb
3
will
be
brighter
than
1.) bulb 3 will be brighter than11oror22but
butnot
not1+2
1+2
2.)
2.)bulb
bulb33will
willbe
bebrighter
brighterthan
than1+2
1+2
3.)
3.)bulb
bulb33will
willbe
beasasdimmer
dimmerthan
thaneither
either11oror22
Prediction
Prediction#2:
#2:Bulbs
Bulbs44&&55 are
areconnected
connectedfirst.
first.IfIf 66isisconnected
connectednext,
next,
1.)
1.)bulb
bulb44will
willbe
bebrighter
brighterthan
thanbefore
before
2.)
bulb
4
will
be
dimmer
than
before
2.) bulb 4 will be dimmer than before
3.)
3.)bulb
bulb44will
willbe
bethe
thesame
sameasasbefore
before
Prediction
Prediction#3:
#3:All
Allbulbs
bulbsare
areconnected.
connected.The
Thebrightest
brightestbulb
bulbisis
1.)
1.)Bulb
Bulb#1
#1
2.)
bulb
#2
2.) bulb #2
3.)
3.)bulb
bulb#3
#3
4.)
bulb
#4
4.) bulb #4
5.)
5.)bulb
bulb#5
#5
6.)
6.)bulb
bulb#6
#6
Concept
Concept Test:
Test: An
Anammeter
ammeterAAisisconnected
connected
between
betweenpoints
pointsaaand
andbbin
inthe
thecircuit
circuitbelow,
below,
in
inwhich
whichthe
thefour
fourresistors
resistorsare
areidentical.
identical.
The
Thecurrent
currentii through
throughthe
theammeter
ammeterisis
i
1.1.I/2.
I/2.
2.2.I/4.
I/4.
3.3.zero.
zero.
4.4.need
needmore
moreinformation
information
Exercise:
Exercise: Twelve
Twelve identical
identical resistors,
resistors, each
each
of
of resistance
resistance R,
R, are
are connected
connected as
as edges
edges of
of
aa cube,
cube, as
as shown
shown in
in the
the figure.
figure. What
What is
is the
the
equivalent
equivalent resistance
resistance between
between two
two
diagonally
diagonally opposite
opposite nodes
nodes (say,
(say, aa and
and d)
d) ??
RC circuits
• Circuit containing a resistance R and a
capacitor C
+
-
E
Question:Can such a circuit sustain a constant
current ?
1. Yes
2. No
3. Depends on values of C and R
Concept
Concept Test:
Test: In
Inthe
thecircuit
circuitshown
shownbelow,
below,
the
thecapacitor
capacitorisischarged
chargedto
toaapotential
potentialdifference
difference
VV00..The
Theswitch
switchisisinitially
initiallyopen,
open,but
butthen
thenthrown
thrown
closed.
closed.Immediately
Immediatelyafter
afterthe
theswitch
switchisisclosed,
closed,
the
thecurrent
currentin
inthe
thecircuit
circuitisis
1.1.
2.2.
3.3.
VV00/R
/R
zero
zero
need
needmore
moreinfo
info
Concept
Concept Test:
Test: The
Thecapacitor
capacitorin
inthe
thecircuit
circuit
below
belowisisinitially
initiallyuncharged.
uncharged.Immediately
Immediatelyafter
after
the
theswitch
switchisisclosed,
closed,
a.)
a.)the
thecurrent
currentisis
isis
1.1.
2.2.
3.3.
E/R
E/R
zero
zero
need
needmore
moreinfo
info
b.)
b.)VVacross
acrossthe
thecapacitor
capacitor
1.1.EE
2.2.zero
zero
3.3.need
needmore
moreinfo
info
Demonstration Part I
S1
R1
E
S2
R2
C
When the switch S1 is closed, the intensity
of the bulb R1
1. is initially high and then gradually drops
2. gradually increases then drops to zero
3. remains zero (does not shine)
Demo: Part II
S1
R1
E
S2
R2
C
S1 is closed, and then opened again. If S2 is now
closed, the intensity of the bulb R2
1. is initially high and then gradually drops
2. gradually increases then drops to zero
3. remains zero.
What happens to bulb R1?
1. is initially high and then gradually drops
2. gradually increases then drops to zero
3. does not shine
S1
S2
R
E
R
C
Switch S2 is kept closed. What is the current
through the battery
a.) immediately after closing the switch
b.) steady state current
c.) what is the maximum voltage across C?
Download