1. Solving Series circuits
How to
Whiteboards

2. A Series Circuit has many voltages, but only one current
Note that the total voltage drops add to source voltage
1  V1
V1 = IR = (3 A)(1 ) = 3 V
24 V
V2 = IR = (3 A)(2 ) = 6 V
2  V2 A2
V3 = IR = (3 A)(5 ) = 15 V
5  V3 A3
How to solve series:
1. Find the total resistance (1  + 2  + 5  = 8 )
2. Find the one current (I = V/R = (24 V)/(8 ) = 3 A - all
the ammeters read 3 A)
3. Use V = IR to find voltages (voltage drops)

3. I A1 A2 R1 R2 R3
Analogy - ping pong balls - electrons
All start moving at once/speed of impulse, speed of particles
Resistance anywhere along the tube limits flow everywhere

4. Whiteboards
1 | 2 | 3 | 4

5. What is the Total resistance?
11 
5 
7 
20.0 V
R tot = R1 + R2 + R3 ...
= 5  + 7  + 11  = 23 
23 

6. What is the reading on both ammeters? (The one current)
(answer with 3 SF)
5 
7 
11  A2 A1
20 V
I = V/R
= (20 V)/(23 ) = = .870 A
.870 A

7. What do the voltmeters read? (3 SF)
11 
5 
7 
20.0 V
V = IR
V1 = (5 )(.8696 A) = 4.35 V
V2 = (18 )(.8696 A) = 15.7 V
4.35 V, 15.7 V

8. What do the voltmeters read? (3 SF)
11 
9 
5 
35 V
13 
3 
R = 41 , I = A
V = IR
V1 = (5 )(.8537 A) = 4.27 V
V2 = (20 )(.8537 A) = 17.1 V
V3 = (13 )(.8537 A) = 11.1 V V3
4.27 V, 17.1 V, 11.1 V

9. What do the voltmeters read? (3 SF)
200 
90 
500  V3
110 
120 V
130 
R = 1030 , I = A
V = IR
V1 = (500 )(.1165 A) = 58.3 V
V2 = (90 )(.1165 A) = 10.5 V
V3 = (330 )(.1165 A) = 38.4 V
58.3 V, 10.5 V, 38.4 V

10. What is the value of the mystery resistor if V1 reads 3.17 V (3 SF)
??? 
5 
7 
20 V
I = V/R = (3.17 V)/(5 )= .634 A
Rtot = V/I = (20 V)/(.634 A) = 
Rtot = 5  + 7  + ?? = 
?? = 19.5 
19.5 

11. V3 A3