1. Series Circuits:
Other
examples:

2. Series circuits - ________________________________________
_________________________________________
have only 1 path for current
could have switches, etc. I
circuit
element ___ 1
wire
wire
________
potential
high +
voltage
source
circuit
element ___ 2
low -
________
potential
wire
circuit
element ___
wire 3 I
Assume:
1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
4. _____________________________________________________
All energy provided by source is used in the elements
Wires have no potential drop (voltage) across them
Pos. current is out of the “high” voltage side
No charge is “lost.” All current returns to the source.

3. _______________ Conservation: V = V1 + V2 Charge
For a
circuit
with 2
resistors: I V I1 V1 R1 I2 R2 V2
Energy
_______________ Conservation: V =
V1 + V2
Charge
_______________ Conservation: I =
I1 = I2
Equivalent
_______________ (Total) Resistance: Req =
R1 + R2
__________ Law applies to the total: V =
and to each individual element: V1 =
V2 =
Ohm’s
I Req
I1R1
I2R2

5. V = IR
Ohm’s
Law
I = V/R

6. Ex. Find all the voltages and currents in the circuit below:
I = I1 = I2
V1 = I1R1
V1 = I1 = R1 =
5.0 V
0.125 A
40 W
V2 = I2R2
V2 = I2 = R2 =
15.0 V
0.125 A
120 W
20. V
20/160 A
V = I = Req =
0.125 A
160 W
I = V/Req
Req = R1 + R2

7. Form the _________ of each resistance to Req = _______ ,
and then multiply by the __________ voltage V
ratio
160 W
total
V =
20. V R1
40 W
40 W
x 20 V =
5 V
Req
160 W
120 W R2
120 W
x 20 V =
15 V
Req
160 W
V “divides up” ______________________________ as the R’s
This is because ___________ R requires _________ energy.
Series circuits are _______________________________.
in the same proportion
more
more
voltage dividers

8. Plot V vs. “distance around circuit.”
back to ____
side of the
battery +
Plot V vs. “distance around circuit.”
____ side of
battery +
wire 20
V dropped across
the ______ resistor
40 W 15
wire
potential
difference
(V)
V dropped
across the
______ R -
at the ___
side of the
battery
160 W
wire
distance around circuit
______ drop across wires because we assume _________ No
R = 0

9. “I is ______________ everywhere in ___________ circuit” does
Important:
“I is ______________ everywhere in ___________ circuit” does
NOT mean that I is ___________ in _________________ circuit!
the same
a series
the same
every other I=
I1=
I2=
10/100 = .1 A
10. V
R1=
25 W
.1 A
R2 =
75 W
.1 A I=
I1=
I2=
I3 =
10/200 = .05 A
R1=
100 W
25 W
10. V
R2=
.05 A
.05 A
R3=
75 W
.05 A
same
I is still the _______________ in all parts of the second
circuit, but it is a ________________ I than the first one!
different

10. If you replace the resistors of a
circuit with one resistor, the total I would be the same
Equivalent resistance: _________________________________
________________________________________________________
Replacing this part of the
circuit with a single
_______________ resistor:
Req = R1 + R2 = =
20. V
40 W
equivalent
40 W W
120 W
160 W
…gives you this circuit: V
Req
The total I =
= V
160 W
20. V
Req =
160 W
= A
This is the ____________ as before.
same I

11. All _______________ circuits can be ___________________ in this way.
series
simplified A.
Req =
_____ W
V =
20 V
V =
20 V
50 W
200
150 W B.
Req =
_____ W
8 W
V =
12 V
16 W 24
V =
12 V
voltage source
This can be done even if the ______________________ is not shown. C.
Req =
_____ W
70 W 90
20 W D.
10 W
Req =
_____ W
5 W 50
15 W
20 W
Req results in the _____________ as the _________________ circuit.
same I
original

12. To measure I1, the current through R1, _________________
Meter
__________ Hookups:
Original
circuit: R1 V R2
disconnect
To measure I1, the current through R1, _________________
the circuit and _____________ an ________________ next to R1
insert
ammeter
insert
disconnect A V R1 R1 V R2 R2
Other
possibilities: R1 V V R1 R2 R2 A A
___ is the same everywhere, so _________________________ I
anywhere gives same I.

13. To measure, V1, the voltage across R1, __________disconnect
the circuit. Simply connect the ______________ across R1
do NOT
voltmeter V R1 R2 V R1 R2
Original
circuit: V
Other
possibilities: V R1 R2 V V V R1 R2
Similarly, to measure the _________ voltage V or V2:
total V R1 R2 V R1 R2 V V