Lecture 13—Circuits part 2

Monday, February 16

Series Resistors

Slide 23-17

In series, current the same in both resistors.

, 1 2 1 2

, 1 2

eq series

eq series

V IR V V IR IR

R R R

Parallel Resistors

Slide 23-18

In parallel, voltage is the same.

1 2, 1 2

, 1 2

1 1 1

eq par

eq par

V V VI I I

R R R

R R R

What is the equivalent resistance of the following circuit?

Find the current in and the potential difference across each element in the following circuit.

Slide 23-21

What is the potential difference across the 200 resistor?

2 v

3 v

4.5 v

7.5 v

Not

enou

gh in

f...

20% 20% 20%20%20%

1. 2 v2. 3 v3. 4.5 v4. 7.5 v5. Not enough info

Find equivalent resistor

• Start at right side:– Series eq = 15Ω

– Two 15Ω in parallel• Par eq = 7.5 Ω

10Ω 15 15

Continue, diagram is now

Now in series equivalent = 10Ω

Now in parallelequivalent = 5Ω

10 7.5

2.55.0

10

10

5.0

Continue

• Finally in series:– Req =10 Ω

5

5.0

Now find all currents and voltages

• Find current in equivalent resistor

10v10

101 A

10eqeq

VI

R

Homework due Friday

• 22: CQ9, CQ11, CQ12, CQ15, 28, 31, 32, 35, 49, 61, 62, WB 22: 8-14

• CQ9 simple loop• CQ11 R=ρL/A• 35• WB22-10

Homework due Today

• 23: 4-5 Measuring current and voltage, complex circuits—how to simplify

• 23: CQ1, CQ2, CQ3, 1, 4, 5, 6, 7, 10, 11, 15, 47, 52, WB 23: 1-6

• CQ2• 1, 5, 7, 47• WB23: 3,5